Abseil Common Libraries (C++) (grcp 依赖) https://abseil.io/
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// Copyright 2017 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
7 years ago
#include "absl/synchronization/mutex.h"
#ifdef _WIN32
#include <windows.h>
#ifdef ERROR
#undef ERROR
#endif
#else
#include <fcntl.h>
#include <pthread.h>
#include <sched.h>
#include <sys/time.h>
#endif
#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <algorithm>
#include <atomic>
#include <cinttypes>
#include <thread> // NOLINT(build/c++11)
#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/base/dynamic_annotations.h"
#include "absl/base/internal/atomic_hook.h"
#include "absl/base/internal/cycleclock.h"
#include "absl/base/internal/hide_ptr.h"
7 years ago
#include "absl/base/internal/low_level_alloc.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/base/internal/spinlock.h"
#include "absl/base/internal/sysinfo.h"
#include "absl/base/internal/thread_identity.h"
#include "absl/base/port.h"
#include "absl/debugging/stacktrace.h"
#include "absl/debugging/symbolize.h"
7 years ago
#include "absl/synchronization/internal/graphcycles.h"
#include "absl/synchronization/internal/per_thread_sem.h"
#include "absl/time/time.h"
using absl::base_internal::CurrentThreadIdentityIfPresent;
using absl::base_internal::PerThreadSynch;
using absl::base_internal::ThreadIdentity;
using absl::synchronization_internal::GetOrCreateCurrentThreadIdentity;
using absl::synchronization_internal::GraphCycles;
using absl::synchronization_internal::GraphId;
using absl::synchronization_internal::InvalidGraphId;
using absl::synchronization_internal::KernelTimeout;
using absl::synchronization_internal::PerThreadSem;
extern "C" {
ABSL_ATTRIBUTE_WEAK void AbslInternalMutexYield() { std::this_thread::yield(); }
} // extern "C"
namespace absl {
Export of internal Abseil changes -- c99f979ad34f155fbeeea69b88bdc7458d89a21c by Derek Mauro <dmauro@google.com>: Remove a floating point division by zero test. This isn't testing behavior related to the library, and MSVC warns about it in opt mode. PiperOrigin-RevId: 285220804 -- 68b015491f0dbf1ab547994673281abd1f34cd4b by Gennadiy Rozental <rogeeff@google.com>: This CL introduces following changes to the class FlagImpl: * We eliminate the CommandLineFlagLocks struct. Instead callback guard and callback function are combined into a single CallbackData struct, while primary data lock is stored separately. * CallbackData member of class FlagImpl is initially set to be nullptr and is only allocated and initialized when a flag's callback is being set. For most flags we do not pay for the extra space and extra absl::Mutex now. * Primary data guard is stored in data_guard_ data member. This is a properly aligned character buffer of necessary size. During initialization of the flag we construct absl::Mutex in this space using placement new call. * We now avoid extra value copy after successful attempt to parse value out of string. Instead we swap flag's current value with tentative value we just produced. PiperOrigin-RevId: 285132636 -- ed45d118fb818969eb13094cf7827c885dfc562c by Tom Manshreck <shreck@google.com>: Change null-term* (and nul-term*) to NUL-term* in comments PiperOrigin-RevId: 285036610 -- 729619017944db895ce8d6d29c1995aa2e5628a5 by Derek Mauro <dmauro@google.com>: Use the Posix implementation of thread identity on MinGW. Some versions of MinGW suffer from thread_local bugs. PiperOrigin-RevId: 285022920 -- 39a25493503c76885bc3254c28f66a251c5b5bb0 by Greg Falcon <gfalcon@google.com>: Implementation detail change. Add further ABSL_NAMESPACE_BEGIN and _END annotation macros to files in Abseil. PiperOrigin-RevId: 285012012 GitOrigin-RevId: c99f979ad34f155fbeeea69b88bdc7458d89a21c Change-Id: I4c85d3704e45d11a9ac50d562f39640a6adbedc1
5 years ago
ABSL_NAMESPACE_BEGIN
7 years ago
namespace {
#if defined(THREAD_SANITIZER)
constexpr OnDeadlockCycle kDeadlockDetectionDefault = OnDeadlockCycle::kIgnore;
#else
constexpr OnDeadlockCycle kDeadlockDetectionDefault = OnDeadlockCycle::kAbort;
#endif
ABSL_CONST_INIT std::atomic<OnDeadlockCycle> synch_deadlock_detection(
kDeadlockDetectionDefault);
ABSL_CONST_INIT std::atomic<bool> synch_check_invariants(false);
// ------------------------------------------ spinlock support
// Make sure read-only globals used in the Mutex code are contained on the
// same cacheline and cacheline aligned to eliminate any false sharing with
// other globals from this and other modules.
static struct MutexGlobals {
MutexGlobals() {
// Find machine-specific data needed for Delay() and
// TryAcquireWithSpinning(). This runs in the global constructor
// sequence, and before that zeros are safe values.
num_cpus = absl::base_internal::NumCPUs();
spinloop_iterations = num_cpus > 1 ? 1500 : 0;
}
int num_cpus;
int spinloop_iterations;
// Pad this struct to a full cacheline to prevent false sharing.
char padding[ABSL_CACHELINE_SIZE - 2 * sizeof(int)];
} ABSL_CACHELINE_ALIGNED mutex_globals;
static_assert(
sizeof(MutexGlobals) == ABSL_CACHELINE_SIZE,
"MutexGlobals must occupy an entire cacheline to prevent false sharing");
Export of internal Abseil changes -- 1bc4d36e13fb9175ea8cdaa00213aa9d4417c669 by Andy Getzendanner <durandal@google.com>: Fix pointer format specifier in documentation Import of https://github.com/abseil/abseil-cpp/pull/614 PiperOrigin-RevId: 293227540 -- c7b43b30493c4fb5f2ec3264672b08bfe1ea3709 by Abseil Team <absl-team@google.com>: Internal change. PiperOrigin-RevId: 293160245 -- 64439365e2b4a0b5e51ae0a7dafdb15912402dfd by Shahriar Rouf <nafi@google.com>: Add benchmarks for string_view: BM_CompareFirstOneLess and BM_CompareSecondOneLess. PiperOrigin-RevId: 293031676 -- b273b420cab24a6e3f487430987e09f4eb1caec4 by Greg Falcon <gfalcon@google.com>: Remove an unreachable line from charconv.cc. Fixes github issue #613. PiperOrigin-RevId: 292980167 -- 70babb5f7a3d9fdd00a2b3085c3c2b9fe0265c79 by Gennadiy Rozental <rogeeff@google.com>: Move GetFlag implementation into FlagImpl. This change will allow us to hide details of GetFlag overloads inside implementation detais. Eventually we'll migrate to a different implementation. No semantic changes in this CL. PiperOrigin-RevId: 292930847 -- 94bee7b7cc31e0167ee4b953281c1e78c96a574a by Abseil Team <absl-team@google.com>: Clarification in absl::Exponential documentation. PiperOrigin-RevId: 292912672 -- d6916d30c5c1d3ee9ae46d69ec0a166a760c99c7 by Derek Mauro <dmauro@google.com>: Make AtomicHook constant-initializable on Clang for Windows. Only mark AtomicHook as constant-initializable on platforms where it is actually constant-initializable. PiperOrigin-RevId: 292655939 GitOrigin-RevId: 1bc4d36e13fb9175ea8cdaa00213aa9d4417c669 Change-Id: I090b231a0ca0d92868e494ab5b3fa86c902889d5
5 years ago
ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
absl::base_internal::AtomicHook<void (*)(int64_t wait_cycles)>
submit_profile_data;
ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES absl::base_internal::AtomicHook<void (*)(
const char *msg, const void *obj, int64_t wait_cycles)>
mutex_tracer;
ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
absl::base_internal::AtomicHook<void (*)(const char *msg, const void *cv)>
cond_var_tracer;
ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES absl::base_internal::AtomicHook<
bool (*)(const void *pc, char *out, int out_size)>
symbolizer(absl::Symbolize);
7 years ago
} // namespace
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
static inline bool EvalConditionAnnotated(const Condition *cond, Mutex *mu,
bool locking, bool trylock,
bool read_lock);
7 years ago
void RegisterMutexProfiler(void (*fn)(int64_t wait_timestamp)) {
submit_profile_data.Store(fn);
}
void RegisterMutexTracer(void (*fn)(const char *msg, const void *obj,
int64_t wait_cycles)) {
mutex_tracer.Store(fn);
}
void RegisterCondVarTracer(void (*fn)(const char *msg, const void *cv)) {
cond_var_tracer.Store(fn);
}
void RegisterSymbolizer(bool (*fn)(const void *pc, char *out, int out_size)) {
symbolizer.Store(fn);
}
// spinlock delay on iteration c. Returns new c.
namespace {
enum DelayMode { AGGRESSIVE, GENTLE };
};
static int Delay(int32_t c, DelayMode mode) {
// If this a uniprocessor, only yield/sleep. Otherwise, if the mode is
// aggressive then spin many times before yielding. If the mode is
// gentle then spin only a few times before yielding. Aggressive spinning is
// used to ensure that an Unlock() call, which must get the spin lock for
// any thread to make progress gets it without undue delay.
int32_t limit = (mutex_globals.num_cpus > 1) ?
((mode == AGGRESSIVE) ? 5000 : 250) : 0;
if (c < limit) {
c++; // spin
} else {
ABSL_TSAN_MUTEX_PRE_DIVERT(nullptr, 0);
7 years ago
if (c == limit) { // yield once
AbslInternalMutexYield();
c++;
} else { // then wait
absl::SleepFor(absl::Microseconds(10));
c = 0;
}
ABSL_TSAN_MUTEX_POST_DIVERT(nullptr, 0);
7 years ago
}
return (c);
}
// --------------------------Generic atomic ops
// Ensure that "(*pv & bits) == bits" by doing an atomic update of "*pv" to
// "*pv | bits" if necessary. Wait until (*pv & wait_until_clear)==0
// before making any change.
// This is used to set flags in mutex and condition variable words.
static void AtomicSetBits(std::atomic<intptr_t>* pv, intptr_t bits,
intptr_t wait_until_clear) {
intptr_t v;
do {
v = pv->load(std::memory_order_relaxed);
} while ((v & bits) != bits &&
((v & wait_until_clear) != 0 ||
!pv->compare_exchange_weak(v, v | bits,
std::memory_order_release,
std::memory_order_relaxed)));
}
// Ensure that "(*pv & bits) == 0" by doing an atomic update of "*pv" to
// "*pv & ~bits" if necessary. Wait until (*pv & wait_until_clear)==0
// before making any change.
// This is used to unset flags in mutex and condition variable words.
static void AtomicClearBits(std::atomic<intptr_t>* pv, intptr_t bits,
intptr_t wait_until_clear) {
intptr_t v;
do {
v = pv->load(std::memory_order_relaxed);
} while ((v & bits) != 0 &&
((v & wait_until_clear) != 0 ||
!pv->compare_exchange_weak(v, v & ~bits,
std::memory_order_release,
std::memory_order_relaxed)));
}
//------------------------------------------------------------------
// Data for doing deadlock detection.
static absl::base_internal::SpinLock deadlock_graph_mu(
absl::base_internal::kLinkerInitialized);
// graph used to detect deadlocks.
static GraphCycles *deadlock_graph ABSL_GUARDED_BY(deadlock_graph_mu)
ABSL_PT_GUARDED_BY(deadlock_graph_mu);
7 years ago
//------------------------------------------------------------------
// An event mechanism for debugging mutex use.
// It also allows mutexes to be given names for those who can't handle
// addresses, and instead like to give their data structures names like
// "Henry", "Fido", or "Rupert IV, King of Yondavia".
namespace { // to prevent name pollution
enum { // Mutex and CondVar events passed as "ev" to PostSynchEvent
// Mutex events
SYNCH_EV_TRYLOCK_SUCCESS,
SYNCH_EV_TRYLOCK_FAILED,
SYNCH_EV_READERTRYLOCK_SUCCESS,
SYNCH_EV_READERTRYLOCK_FAILED,
SYNCH_EV_LOCK,
SYNCH_EV_LOCK_RETURNING,
SYNCH_EV_READERLOCK,
SYNCH_EV_READERLOCK_RETURNING,
SYNCH_EV_UNLOCK,
SYNCH_EV_READERUNLOCK,
// CondVar events
SYNCH_EV_WAIT,
SYNCH_EV_WAIT_RETURNING,
SYNCH_EV_SIGNAL,
SYNCH_EV_SIGNALALL,
};
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
enum { // Event flags
SYNCH_F_R = 0x01, // reader event
SYNCH_F_LCK = 0x02, // PostSynchEvent called with mutex held
SYNCH_F_TRY = 0x04, // TryLock or ReaderTryLock
SYNCH_F_UNLOCK = 0x08, // Unlock or ReaderUnlock
7 years ago
SYNCH_F_LCK_W = SYNCH_F_LCK,
SYNCH_F_LCK_R = SYNCH_F_LCK | SYNCH_F_R,
};
} // anonymous namespace
// Properties of the events.
static const struct {
int flags;
const char *msg;
} event_properties[] = {
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
{SYNCH_F_LCK_W | SYNCH_F_TRY, "TryLock succeeded "},
{0, "TryLock failed "},
{SYNCH_F_LCK_R | SYNCH_F_TRY, "ReaderTryLock succeeded "},
{0, "ReaderTryLock failed "},
{0, "Lock blocking "},
{SYNCH_F_LCK_W, "Lock returning "},
{0, "ReaderLock blocking "},
{SYNCH_F_LCK_R, "ReaderLock returning "},
{SYNCH_F_LCK_W | SYNCH_F_UNLOCK, "Unlock "},
{SYNCH_F_LCK_R | SYNCH_F_UNLOCK, "ReaderUnlock "},
{0, "Wait on "},
{0, "Wait unblocked "},
{0, "Signal on "},
{0, "SignalAll on "},
7 years ago
};
Export of internal Abseil changes. -- bdce7e57e9e886eff1114d0266781b443f7ec639 by Derek Mauro <dmauro@google.com>: Change {Get|Set}EnvironmentVariable to {Get|Set}EnvironmentVariableA for compatibility with /DUNICODE. PiperOrigin-RevId: 239229514 -- 2276ed502326a044a84060d34eb19d499e3a3be2 by Derek Mauro <dmauro@google.com>: Import of CCTZ from GitHub. PiperOrigin-RevId: 239228622 -- a462efb970ff43b08a362ef2343fb75ac1295a50 by Derek Mauro <dmauro@google.com>: Adding linking of CoreFoundation to CMakeLists in absl/time. Import https://github.com/abseil/abseil-cpp/pull/280. Fix #283 PiperOrigin-RevId: 239220785 -- fc23327b97f940c682aae1956cf7a1bf87f88c06 by Derek Mauro <dmauro@google.com>: Add hermetic test script that uses Docker to build with a very recent version of gcc (8.3.0 today) with libstdc++ and bazel. PiperOrigin-RevId: 239220448 -- 418c08a8f6a53e63b84e39473035774417ca3aa7 by Derek Mauro <dmauro@google.com>: Disable part of the variant exeception safety test on move assignment when using versions of libstd++ that contain a bug. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87431#c7 PiperOrigin-RevId: 239062455 -- 799722217aeda79679577843c91d5be62cbcbb42 by Matt Calabrese <calabrese@google.com>: Add internal-only IsSwappable traits corresponding to std::is_swappable and std::is_nothrow_swappable, which are used with the swap implementations of optional and variant. PiperOrigin-RevId: 239049448 -- aa46a036038a3de5c68ac5e5d3b4bf76f818d2ea by CJ Johnson <johnsoncj@google.com>: Make InlinedVectorStorage constructor explicit PiperOrigin-RevId: 239044361 -- 17949715b3aa21c794701f69f2154e91b6acabc3 by CJ Johnson <johnsoncj@google.com>: Add absl namesapce to internal/inlined_vector.h PiperOrigin-RevId: 239030789 -- 834628325953078cc08ed10d23bb8890e5bec897 by Derek Mauro <dmauro@google.com>: Add test script that uses Docker to build Abseil with gcc-4.8, libstdc++, and cmake. PiperOrigin-RevId: 239028433 -- 80fe24149ed73ed2ced995ad1e372fb060c60427 by CJ Johnson <johnsoncj@google.com>: Factors data members of InlinedVector into an impl type called InlinedVectorStorage so that (in future changes) the contents of a vector can be grouped together with a single pointer. PiperOrigin-RevId: 239021086 -- 585331436d5d4d79f845e45dcf79d918a0dc6169 by Derek Mauro <dmauro@google.com>: Add -Wno-missing-field-initializers to gcc compiler flags. gcc-4.x has spurious missing field initializer warnings. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=36750 PiperOrigin-RevId: 239017217 -- 94602fe4e33ee3a552a7f2939c0f57a992f55075 by Abseil Team <absl-team@google.com>: Formatting fixes. PiperOrigin-RevId: 238983038 -- a1c1b63c08505574e0a8c491561840cecb2bb93e by Derek Mauro <dmauro@google.com>: Add hermetic test script that uses Docker to build with a very recent version of clang with libc++ and bazel. PiperOrigin-RevId: 238669118 -- e525f8d20bc2f79a0d69336b902f63858f3bff9d by Derek Mauro <dmauro@google.com>: Disable the test optionalTest.InPlaceTSFINAEBug until libc++ is updated. PiperOrigin-RevId: 238661703 -- f99a2a0b5ec424a059678f7f226600f137b4c74e by Derek Mauro <dmauro@google.com>: Correct the check for the FlatHashMap-Any test bug (list conditions instead of platforms when possible) PiperOrigin-RevId: 238653344 -- 777928035dbcbf39f361eb7d10dc3696822f692f by Jon Cohen <cohenjon@google.com>: Add install rules for Abseil CMake. These are attempted to be limited to in-project installation. This serves two purposes -- first it's morally the same as using Abseil in-source, except you don't have to rebuild us every time. Second, the presence of an install rule makes life massively simpler for package manager maintainers. Currently this doesn't install absl tests or testonly libraries. This can be added in a follow-up patch. Fixes #38, Fixes #80, Closes #182 PiperOrigin-RevId: 238645836 -- ded1c6ce697c191b7a6ff14572b3e6d183117b2c by Derek Mauro <dmauro@google.com>: Add hermetic test script that uses Docker to build with a very recent version of clang with libstdc++ and bazel. PiperOrigin-RevId: 238517815 GitOrigin-RevId: bdce7e57e9e886eff1114d0266781b443f7ec639 Change-Id: I6f745869cb8ef63851891ccac05ae9a7dd241c4f
6 years ago
7 years ago
static absl::base_internal::SpinLock synch_event_mu(
absl::base_internal::kLinkerInitialized);
// protects synch_event
// Hash table size; should be prime > 2.
// Can't be too small, as it's used for deadlock detection information.
static const uint32_t kNSynchEvent = 1031;
static struct SynchEvent { // this is a trivial hash table for the events
// struct is freed when refcount reaches 0
int refcount ABSL_GUARDED_BY(synch_event_mu);
7 years ago
// buckets have linear, 0-terminated chains
SynchEvent *next ABSL_GUARDED_BY(synch_event_mu);
7 years ago
// Constant after initialization
uintptr_t masked_addr; // object at this address is called "name"
// No explicit synchronization used. Instead we assume that the
// client who enables/disables invariants/logging on a Mutex does so
// while the Mutex is not being concurrently accessed by others.
void (*invariant)(void *arg); // called on each event
void *arg; // first arg to (*invariant)()
bool log; // logging turned on
// Constant after initialization
Export of internal Abseil changes -- c99f979ad34f155fbeeea69b88bdc7458d89a21c by Derek Mauro <dmauro@google.com>: Remove a floating point division by zero test. This isn't testing behavior related to the library, and MSVC warns about it in opt mode. PiperOrigin-RevId: 285220804 -- 68b015491f0dbf1ab547994673281abd1f34cd4b by Gennadiy Rozental <rogeeff@google.com>: This CL introduces following changes to the class FlagImpl: * We eliminate the CommandLineFlagLocks struct. Instead callback guard and callback function are combined into a single CallbackData struct, while primary data lock is stored separately. * CallbackData member of class FlagImpl is initially set to be nullptr and is only allocated and initialized when a flag's callback is being set. For most flags we do not pay for the extra space and extra absl::Mutex now. * Primary data guard is stored in data_guard_ data member. This is a properly aligned character buffer of necessary size. During initialization of the flag we construct absl::Mutex in this space using placement new call. * We now avoid extra value copy after successful attempt to parse value out of string. Instead we swap flag's current value with tentative value we just produced. PiperOrigin-RevId: 285132636 -- ed45d118fb818969eb13094cf7827c885dfc562c by Tom Manshreck <shreck@google.com>: Change null-term* (and nul-term*) to NUL-term* in comments PiperOrigin-RevId: 285036610 -- 729619017944db895ce8d6d29c1995aa2e5628a5 by Derek Mauro <dmauro@google.com>: Use the Posix implementation of thread identity on MinGW. Some versions of MinGW suffer from thread_local bugs. PiperOrigin-RevId: 285022920 -- 39a25493503c76885bc3254c28f66a251c5b5bb0 by Greg Falcon <gfalcon@google.com>: Implementation detail change. Add further ABSL_NAMESPACE_BEGIN and _END annotation macros to files in Abseil. PiperOrigin-RevId: 285012012 GitOrigin-RevId: c99f979ad34f155fbeeea69b88bdc7458d89a21c Change-Id: I4c85d3704e45d11a9ac50d562f39640a6adbedc1
5 years ago
char name[1]; // actually longer---NUL-terminated std::string
} * synch_event[kNSynchEvent] ABSL_GUARDED_BY(synch_event_mu);
7 years ago
// Ensure that the object at "addr" has a SynchEvent struct associated with it,
// set "bits" in the word there (waiting until lockbit is clear before doing
// so), and return a refcounted reference that will remain valid until
// UnrefSynchEvent() is called. If a new SynchEvent is allocated,
// the string name is copied into it.
7 years ago
// When used with a mutex, the caller should also ensure that kMuEvent
// is set in the mutex word, and similarly for condition variables and kCVEvent.
static SynchEvent *EnsureSynchEvent(std::atomic<intptr_t> *addr,
const char *name, intptr_t bits,
intptr_t lockbit) {
uint32_t h = reinterpret_cast<intptr_t>(addr) % kNSynchEvent;
SynchEvent *e;
// first look for existing SynchEvent struct..
synch_event_mu.Lock();
for (e = synch_event[h];
e != nullptr && e->masked_addr != base_internal::HidePtr(addr);
7 years ago
e = e->next) {
}
if (e == nullptr) { // no SynchEvent struct found; make one.
if (name == nullptr) {
name = "";
}
size_t l = strlen(name);
e = reinterpret_cast<SynchEvent *>(
base_internal::LowLevelAlloc::Alloc(sizeof(*e) + l));
e->refcount = 2; // one for return value, one for linked list
e->masked_addr = base_internal::HidePtr(addr);
7 years ago
e->invariant = nullptr;
e->arg = nullptr;
e->log = false;
strcpy(e->name, name); // NOLINT(runtime/printf)
e->next = synch_event[h];
AtomicSetBits(addr, bits, lockbit);
synch_event[h] = e;
} else {
e->refcount++; // for return value
}
synch_event_mu.Unlock();
return e;
}
// Deallocate the SynchEvent *e, whose refcount has fallen to zero.
static void DeleteSynchEvent(SynchEvent *e) {
base_internal::LowLevelAlloc::Free(e);
}
// Decrement the reference count of *e, or do nothing if e==null.
static void UnrefSynchEvent(SynchEvent *e) {
if (e != nullptr) {
synch_event_mu.Lock();
bool del = (--(e->refcount) == 0);
synch_event_mu.Unlock();
if (del) {
DeleteSynchEvent(e);
}
}
}
// Forget the mapping from the object (Mutex or CondVar) at address addr
// to SynchEvent object, and clear "bits" in its word (waiting until lockbit
// is clear before doing so).
static void ForgetSynchEvent(std::atomic<intptr_t> *addr, intptr_t bits,
intptr_t lockbit) {
uint32_t h = reinterpret_cast<intptr_t>(addr) % kNSynchEvent;
SynchEvent **pe;
SynchEvent *e;
synch_event_mu.Lock();
for (pe = &synch_event[h];
(e = *pe) != nullptr && e->masked_addr != base_internal::HidePtr(addr);
pe = &e->next) {
7 years ago
}
bool del = false;
if (e != nullptr) {
*pe = e->next;
del = (--(e->refcount) == 0);
}
AtomicClearBits(addr, bits, lockbit);
synch_event_mu.Unlock();
if (del) {
DeleteSynchEvent(e);
}
}
// Return a refcounted reference to the SynchEvent of the object at address
// "addr", if any. The pointer returned is valid until the UnrefSynchEvent() is
// called.
static SynchEvent *GetSynchEvent(const void *addr) {
uint32_t h = reinterpret_cast<intptr_t>(addr) % kNSynchEvent;
SynchEvent *e;
synch_event_mu.Lock();
for (e = synch_event[h];
e != nullptr && e->masked_addr != base_internal::HidePtr(addr);
7 years ago
e = e->next) {
}
if (e != nullptr) {
e->refcount++;
}
synch_event_mu.Unlock();
return e;
}
// Called when an event "ev" occurs on a Mutex of CondVar "obj"
// if event recording is on
static void PostSynchEvent(void *obj, int ev) {
SynchEvent *e = GetSynchEvent(obj);
// logging is on if event recording is on and either there's no event struct,
// or it explicitly says to log
if (e == nullptr || e->log) {
void *pcs[40];
int n = absl::GetStackTrace(pcs, ABSL_ARRAYSIZE(pcs), 1);
// A buffer with enough space for the ASCII for all the PCs, even on a
// 64-bit machine.
char buffer[ABSL_ARRAYSIZE(pcs) * 24];
int pos = snprintf(buffer, sizeof (buffer), " @");
for (int i = 0; i != n; i++) {
pos += snprintf(&buffer[pos], sizeof (buffer) - pos, " %p", pcs[i]);
}
ABSL_RAW_LOG(INFO, "%s%p %s %s", event_properties[ev].msg, obj,
(e == nullptr ? "" : e->name), buffer);
}
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
const int flags = event_properties[ev].flags;
if ((flags & SYNCH_F_LCK) != 0 && e != nullptr && e->invariant != nullptr) {
// Calling the invariant as is causes problems under ThreadSanitizer.
// We are currently inside of Mutex Lock/Unlock and are ignoring all
// memory accesses and synchronization. If the invariant transitively
// synchronizes something else and we ignore the synchronization, we will
// get false positive race reports later.
// Reuse EvalConditionAnnotated to properly call into user code.
struct local {
static bool pred(SynchEvent *ev) {
(*ev->invariant)(ev->arg);
return false;
}
};
Condition cond(&local::pred, e);
Mutex *mu = static_cast<Mutex *>(obj);
const bool locking = (flags & SYNCH_F_UNLOCK) == 0;
const bool trylock = (flags & SYNCH_F_TRY) != 0;
const bool read_lock = (flags & SYNCH_F_R) != 0;
EvalConditionAnnotated(&cond, mu, locking, trylock, read_lock);
7 years ago
}
UnrefSynchEvent(e);
}
//------------------------------------------------------------------
// The SynchWaitParams struct encapsulates the way in which a thread is waiting:
// whether it has a timeout, the condition, exclusive/shared, and whether a
// condition variable wait has an associated Mutex (as opposed to another
// type of lock). It also points to the PerThreadSynch struct of its thread.
// cv_word tells Enqueue() to enqueue on a CondVar using CondVarEnqueue().
//
// This structure is held on the stack rather than directly in
// PerThreadSynch because a thread can be waiting on multiple Mutexes if,
// while waiting on one Mutex, the implementation calls a client callback
// (such as a Condition function) that acquires another Mutex. We don't
// strictly need to allow this, but programmers become confused if we do not
// allow them to use functions such a LOG() within Condition functions. The
// PerThreadSynch struct points at the most recent SynchWaitParams struct when
// the thread is on a Mutex's waiter queue.
struct SynchWaitParams {
SynchWaitParams(Mutex::MuHow how_arg, const Condition *cond_arg,
KernelTimeout timeout_arg, Mutex *cvmu_arg,
PerThreadSynch *thread_arg,
std::atomic<intptr_t> *cv_word_arg)
: how(how_arg),
cond(cond_arg),
timeout(timeout_arg),
cvmu(cvmu_arg),
thread(thread_arg),
cv_word(cv_word_arg),
contention_start_cycles(base_internal::CycleClock::Now()) {}
const Mutex::MuHow how; // How this thread needs to wait.
const Condition *cond; // The condition that this thread is waiting for.
// In Mutex, this field is set to zero if a timeout
// expires.
KernelTimeout timeout; // timeout expiry---absolute time
// In Mutex, this field is set to zero if a timeout
// expires.
Mutex *const cvmu; // used for transfer from cond var to mutex
PerThreadSynch *const thread; // thread that is waiting
// If not null, thread should be enqueued on the CondVar whose state
// word is cv_word instead of queueing normally on the Mutex.
std::atomic<intptr_t> *cv_word;
int64_t contention_start_cycles; // Time (in cycles) when this thread started
// to contend for the mutex.
};
struct SynchLocksHeld {
int n; // number of valid entries in locks[]
bool overflow; // true iff we overflowed the array at some point
struct {
Mutex *mu; // lock acquired
int32_t count; // times acquired
GraphId id; // deadlock_graph id of acquired lock
} locks[40];
// If a thread overfills the array during deadlock detection, we
// continue, discarding information as needed. If no overflow has
// taken place, we can provide more error checking, such as
// detecting when a thread releases a lock it does not hold.
};
// A sentinel value in lists that is not 0.
// A 0 value is used to mean "not on a list".
static PerThreadSynch *const kPerThreadSynchNull =
reinterpret_cast<PerThreadSynch *>(1);
static SynchLocksHeld *LocksHeldAlloc() {
SynchLocksHeld *ret = reinterpret_cast<SynchLocksHeld *>(
base_internal::LowLevelAlloc::Alloc(sizeof(SynchLocksHeld)));
ret->n = 0;
ret->overflow = false;
return ret;
}
// Return the PerThreadSynch-struct for this thread.
static PerThreadSynch *Synch_GetPerThread() {
ThreadIdentity *identity = GetOrCreateCurrentThreadIdentity();
return &identity->per_thread_synch;
}
static PerThreadSynch *Synch_GetPerThreadAnnotated(Mutex *mu) {
if (mu) {
ABSL_TSAN_MUTEX_PRE_DIVERT(mu, 0);
}
PerThreadSynch *w = Synch_GetPerThread();
if (mu) {
ABSL_TSAN_MUTEX_POST_DIVERT(mu, 0);
}
return w;
}
static SynchLocksHeld *Synch_GetAllLocks() {
PerThreadSynch *s = Synch_GetPerThread();
if (s->all_locks == nullptr) {
s->all_locks = LocksHeldAlloc(); // Freed by ReclaimThreadIdentity.
}
return s->all_locks;
}
// Post on "w"'s associated PerThreadSem.
inline void Mutex::IncrementSynchSem(Mutex *mu, PerThreadSynch *w) {
if (mu) {
ABSL_TSAN_MUTEX_PRE_DIVERT(mu, 0);
}
PerThreadSem::Post(w->thread_identity());
if (mu) {
ABSL_TSAN_MUTEX_POST_DIVERT(mu, 0);
}
}
// Wait on "w"'s associated PerThreadSem; returns false if timeout expired.
bool Mutex::DecrementSynchSem(Mutex *mu, PerThreadSynch *w, KernelTimeout t) {
if (mu) {
ABSL_TSAN_MUTEX_PRE_DIVERT(mu, 0);
}
assert(w == Synch_GetPerThread());
static_cast<void>(w);
bool res = PerThreadSem::Wait(t);
if (mu) {
ABSL_TSAN_MUTEX_POST_DIVERT(mu, 0);
}
return res;
}
// We're in a fatal signal handler that hopes to use Mutex and to get
// lucky by not deadlocking. We try to improve its chances of success
// by effectively disabling some of the consistency checks. This will
// prevent certain ABSL_RAW_CHECK() statements from being triggered when
// re-rentry is detected. The ABSL_RAW_CHECK() statements are those in the
// Mutex code checking that the "waitp" field has not been reused.
void Mutex::InternalAttemptToUseMutexInFatalSignalHandler() {
// Fix the per-thread state only if it exists.
ThreadIdentity *identity = CurrentThreadIdentityIfPresent();
if (identity != nullptr) {
identity->per_thread_synch.suppress_fatal_errors = true;
}
// Don't do deadlock detection when we are already failing.
synch_deadlock_detection.store(OnDeadlockCycle::kIgnore,
std::memory_order_release);
}
// --------------------------time support
// Return the current time plus the timeout. Use the same clock as
// PerThreadSem::Wait() for consistency. Unfortunately, we don't have
// such a choice when a deadline is given directly.
static absl::Time DeadlineFromTimeout(absl::Duration timeout) {
#ifndef _WIN32
struct timeval tv;
gettimeofday(&tv, nullptr);
return absl::TimeFromTimeval(tv) + timeout;
#else
return absl::Now() + timeout;
#endif
}
// --------------------------Mutexes
// In the layout below, the msb of the bottom byte is currently unused. Also,
// the following constraints were considered in choosing the layout:
// o Both the debug allocator's "uninitialized" and "freed" patterns (0xab and
// 0xcd) are illegal: reader and writer lock both held.
// o kMuWriter and kMuEvent should exceed kMuDesig and kMuWait, to enable the
// bit-twiddling trick in Mutex::Unlock().
// o kMuWriter / kMuReader == kMuWrWait / kMuWait,
// to enable the bit-twiddling trick in CheckForMutexCorruption().
static const intptr_t kMuReader = 0x0001L; // a reader holds the lock
static const intptr_t kMuDesig = 0x0002L; // there's a designated waker
static const intptr_t kMuWait = 0x0004L; // threads are waiting
static const intptr_t kMuWriter = 0x0008L; // a writer holds the lock
static const intptr_t kMuEvent = 0x0010L; // record this mutex's events
// INVARIANT1: there's a thread that was blocked on the mutex, is
// no longer, yet has not yet acquired the mutex. If there's a
// designated waker, all threads can avoid taking the slow path in
// unlock because the designated waker will subsequently acquire
// the lock and wake someone. To maintain INVARIANT1 the bit is
// set when a thread is unblocked(INV1a), and threads that were
// unblocked reset the bit when they either acquire or re-block
// (INV1b).
static const intptr_t kMuWrWait = 0x0020L; // runnable writer is waiting
// for a reader
static const intptr_t kMuSpin = 0x0040L; // spinlock protects wait list
static const intptr_t kMuLow = 0x00ffL; // mask all mutex bits
static const intptr_t kMuHigh = ~kMuLow; // mask pointer/reader count
// Hack to make constant values available to gdb pretty printer
enum {
kGdbMuSpin = kMuSpin,
kGdbMuEvent = kMuEvent,
kGdbMuWait = kMuWait,
kGdbMuWriter = kMuWriter,
kGdbMuDesig = kMuDesig,
kGdbMuWrWait = kMuWrWait,
kGdbMuReader = kMuReader,
kGdbMuLow = kMuLow,
};
// kMuWrWait implies kMuWait.
// kMuReader and kMuWriter are mutually exclusive.
// If kMuReader is zero, there are no readers.
// Otherwise, if kMuWait is zero, the high order bits contain a count of the
// number of readers. Otherwise, the reader count is held in
// PerThreadSynch::readers of the most recently queued waiter, again in the
// bits above kMuLow.
static const intptr_t kMuOne = 0x0100; // a count of one reader
// flags passed to Enqueue and LockSlow{,WithTimeout,Loop}
static const int kMuHasBlocked = 0x01; // already blocked (MUST == 1)
static const int kMuIsCond = 0x02; // conditional waiter (CV or Condition)
static_assert(PerThreadSynch::kAlignment > kMuLow,
"PerThreadSynch::kAlignment must be greater than kMuLow");
// This struct contains various bitmasks to be used in
// acquiring and releasing a mutex in a particular mode.
struct MuHowS {
// if all the bits in fast_need_zero are zero, the lock can be acquired by
// adding fast_add and oring fast_or. The bit kMuDesig should be reset iff
// this is the designated waker.
intptr_t fast_need_zero;
intptr_t fast_or;
intptr_t fast_add;
intptr_t slow_need_zero; // fast_need_zero with events (e.g. logging)
intptr_t slow_inc_need_zero; // if all the bits in slow_inc_need_zero are
// zero a reader can acquire a read share by
// setting the reader bit and incrementing
// the reader count (in last waiter since
// we're now slow-path). kMuWrWait be may
// be ignored if we already waited once.
};
static const MuHowS kSharedS = {
// shared or read lock
kMuWriter | kMuWait | kMuEvent, // fast_need_zero
kMuReader, // fast_or
kMuOne, // fast_add
kMuWriter | kMuWait, // slow_need_zero
kMuSpin | kMuWriter | kMuWrWait, // slow_inc_need_zero
};
static const MuHowS kExclusiveS = {
// exclusive or write lock
kMuWriter | kMuReader | kMuEvent, // fast_need_zero
kMuWriter, // fast_or
0, // fast_add
kMuWriter | kMuReader, // slow_need_zero
~static_cast<intptr_t>(0), // slow_inc_need_zero
};
static const Mutex::MuHow kShared = &kSharedS; // shared lock
static const Mutex::MuHow kExclusive = &kExclusiveS; // exclusive lock
#ifdef NDEBUG
static constexpr bool kDebugMode = false;
#else
static constexpr bool kDebugMode = true;
#endif
#ifdef THREAD_SANITIZER
static unsigned TsanFlags(Mutex::MuHow how) {
return how == kShared ? __tsan_mutex_read_lock : 0;
}
#endif
static bool DebugOnlyIsExiting() {
return false;
}
Mutex::~Mutex() {
intptr_t v = mu_.load(std::memory_order_relaxed);
if ((v & kMuEvent) != 0 && !DebugOnlyIsExiting()) {
ForgetSynchEvent(&this->mu_, kMuEvent, kMuSpin);
}
if (kDebugMode) {
this->ForgetDeadlockInfo();
}
ABSL_TSAN_MUTEX_DESTROY(this, __tsan_mutex_not_static);
7 years ago
}
void Mutex::EnableDebugLog(const char *name) {
SynchEvent *e = EnsureSynchEvent(&this->mu_, name, kMuEvent, kMuSpin);
e->log = true;
UnrefSynchEvent(e);
}
void EnableMutexInvariantDebugging(bool enabled) {
synch_check_invariants.store(enabled, std::memory_order_release);
}
void Mutex::EnableInvariantDebugging(void (*invariant)(void *),
void *arg) {
if (synch_check_invariants.load(std::memory_order_acquire) &&
invariant != nullptr) {
SynchEvent *e = EnsureSynchEvent(&this->mu_, nullptr, kMuEvent, kMuSpin);
e->invariant = invariant;
e->arg = arg;
UnrefSynchEvent(e);
}
}
void SetMutexDeadlockDetectionMode(OnDeadlockCycle mode) {
synch_deadlock_detection.store(mode, std::memory_order_release);
}
// Return true iff threads x and y are waiting on the same condition for the
// same type of lock. Requires that x and y be waiting on the same Mutex
// queue.
static bool MuSameCondition(PerThreadSynch *x, PerThreadSynch *y) {
return x->waitp->how == y->waitp->how &&
Condition::GuaranteedEqual(x->waitp->cond, y->waitp->cond);
}
// Given the contents of a mutex word containing a PerThreadSynch pointer,
// return the pointer.
static inline PerThreadSynch *GetPerThreadSynch(intptr_t v) {
return reinterpret_cast<PerThreadSynch *>(v & kMuHigh);
}
// The next several routines maintain the per-thread next and skip fields
// used in the Mutex waiter queue.
// The queue is a circular singly-linked list, of which the "head" is the
// last element, and head->next if the first element.
// The skip field has the invariant:
// For thread x, x->skip is one of:
// - invalid (iff x is not in a Mutex wait queue),
// - null, or
// - a pointer to a distinct thread waiting later in the same Mutex queue
// such that all threads in [x, x->skip] have the same condition and
// lock type (MuSameCondition() is true for all pairs in [x, x->skip]).
// In addition, if x->skip is valid, (x->may_skip || x->skip == null)
//
// By the spec of MuSameCondition(), it is not necessary when removing the
// first runnable thread y from the front a Mutex queue to adjust the skip
// field of another thread x because if x->skip==y, x->skip must (have) become
// invalid before y is removed. The function TryRemove can remove a specified
// thread from an arbitrary position in the queue whether runnable or not, so
// it fixes up skip fields that would otherwise be left dangling.
// The statement
// if (x->may_skip && MuSameCondition(x, x->next)) { x->skip = x->next; }
// maintains the invariant provided x is not the last waiter in a Mutex queue
// The statement
// if (x->skip != null) { x->skip = x->skip->skip; }
// maintains the invariant.
// Returns the last thread y in a mutex waiter queue such that all threads in
// [x, y] inclusive share the same condition. Sets skip fields of some threads
// in that range to optimize future evaluation of Skip() on x values in
// the range. Requires thread x is in a mutex waiter queue.
// The locking is unusual. Skip() is called under these conditions:
// - spinlock is held in call from Enqueue(), with maybe_unlocking == false
// - Mutex is held in call from UnlockSlow() by last unlocker, with
// maybe_unlocking == true
// - both Mutex and spinlock are held in call from DequeueAllWakeable() (from
// UnlockSlow()) and TryRemove()
// These cases are mutually exclusive, so Skip() never runs concurrently
// with itself on the same Mutex. The skip chain is used in these other places
// that cannot occur concurrently:
// - FixSkip() (from TryRemove()) - spinlock and Mutex are held)
// - Dequeue() (with spinlock and Mutex held)
// - UnlockSlow() (with spinlock and Mutex held)
// A more complex case is Enqueue()
// - Enqueue() (with spinlock held and maybe_unlocking == false)
// This is the first case in which Skip is called, above.
// - Enqueue() (without spinlock held; but queue is empty and being freshly
// formed)
// - Enqueue() (with spinlock held and maybe_unlocking == true)
// The first case has mutual exclusion, and the second isolation through
// working on an otherwise unreachable data structure.
// In the last case, Enqueue() is required to change no skip/next pointers
// except those in the added node and the former "head" node. This implies
// that the new node is added after head, and so must be the new head or the
// new front of the queue.
static PerThreadSynch *Skip(PerThreadSynch *x) {
PerThreadSynch *x0 = nullptr;
PerThreadSynch *x1 = x;
PerThreadSynch *x2 = x->skip;
if (x2 != nullptr) {
// Each iteration attempts to advance sequence (x0,x1,x2) to next sequence
// such that x1 == x0->skip && x2 == x1->skip
while ((x0 = x1, x1 = x2, x2 = x2->skip) != nullptr) {
x0->skip = x2; // short-circuit skip from x0 to x2
}
x->skip = x1; // short-circuit skip from x to result
}
return x1;
}
// "ancestor" appears before "to_be_removed" in the same Mutex waiter queue.
// The latter is going to be removed out of order, because of a timeout.
// Check whether "ancestor" has a skip field pointing to "to_be_removed",
// and fix it if it does.
static void FixSkip(PerThreadSynch *ancestor, PerThreadSynch *to_be_removed) {
if (ancestor->skip == to_be_removed) { // ancestor->skip left dangling
if (to_be_removed->skip != nullptr) {
ancestor->skip = to_be_removed->skip; // can skip past to_be_removed
} else if (ancestor->next != to_be_removed) { // they are not adjacent
ancestor->skip = ancestor->next; // can skip one past ancestor
} else {
ancestor->skip = nullptr; // can't skip at all
}
}
}
static void CondVarEnqueue(SynchWaitParams *waitp);
// Enqueue thread "waitp->thread" on a waiter queue.
// Called with mutex spinlock held if head != nullptr
// If head==nullptr and waitp->cv_word==nullptr, then Enqueue() is
// idempotent; it alters no state associated with the existing (empty)
// queue.
//
// If waitp->cv_word == nullptr, queue the thread at either the front or
// the end (according to its priority) of the circular mutex waiter queue whose
// head is "head", and return the new head. mu is the previous mutex state,
// which contains the reader count (perhaps adjusted for the operation in
// progress) if the list was empty and a read lock held, and the holder hint if
// the list was empty and a write lock held. (flags & kMuIsCond) indicates
// whether this thread was transferred from a CondVar or is waiting for a
// non-trivial condition. In this case, Enqueue() never returns nullptr
//
// If waitp->cv_word != nullptr, CondVarEnqueue() is called, and "head" is
// returned. This mechanism is used by CondVar to queue a thread on the
// condition variable queue instead of the mutex queue in implementing Wait().
// In this case, Enqueue() can return nullptr (if head==nullptr).
static PerThreadSynch *Enqueue(PerThreadSynch *head,
SynchWaitParams *waitp, intptr_t mu, int flags) {
// If we have been given a cv_word, call CondVarEnqueue() and return
// the previous head of the Mutex waiter queue.
if (waitp->cv_word != nullptr) {
CondVarEnqueue(waitp);
return head;
}
PerThreadSynch *s = waitp->thread;
ABSL_RAW_CHECK(
s->waitp == nullptr || // normal case
s->waitp == waitp || // Fer()---transfer from condition variable
s->suppress_fatal_errors,
"detected illegal recursion into Mutex code");
s->waitp = waitp;
s->skip = nullptr; // maintain skip invariant (see above)
s->may_skip = true; // always true on entering queue
s->wake = false; // not being woken
s->cond_waiter = ((flags & kMuIsCond) != 0);
if (head == nullptr) { // s is the only waiter
s->next = s; // it's the only entry in the cycle
s->readers = mu; // reader count is from mu word
s->maybe_unlocking = false; // no one is searching an empty list
head = s; // s is new head
} else {
PerThreadSynch *enqueue_after = nullptr; // we'll put s after this element
#ifdef ABSL_HAVE_PTHREAD_GETSCHEDPARAM
int64_t now_cycles = base_internal::CycleClock::Now();
if (s->next_priority_read_cycles < now_cycles) {
// Every so often, update our idea of the thread's priority.
// pthread_getschedparam() is 5% of the block/wakeup time;
// base_internal::CycleClock::Now() is 0.5%.
int policy;
struct sched_param param;
Export of internal Abseil changes. -- 22fceefcf070a0cf89bf1846bee16a9d36ad4161 by Derek Mauro <dmauro@google.com>: Use function static for once initialization of flag registry. This is a workaround for the MSVC debug constexpr initialization issue in absl::once_flag. GitHub #304 PiperOrigin-RevId: 248169007 -- 97bbe6a5233802b61e758c55f7ba8926539cc4ca by Chris Kennelly <ckennelly@google.com>: Internal change PiperOrigin-RevId: 248139347 -- e72640ee079b9fa44e2c7f925fa0a608bcfea515 by Derek Mauro <dmauro@google.com>: Re-write flags config. It doesn't have to be written in the convoluted way it currently is in the opensource-only code path. PiperOrigin-RevId: 248010502 -- 2a72552511b8086c78cb43012c1644e519b3807e by Abseil Team <absl-team@google.com>: Handle pthread_getschedparam() failure. Log an error message if pthread_getschedparam() fails. In Android's Media Framework, libminijail (which I believe is a sandbox) aborts the process if pthread_getschedparam() is called: media.swcodec: libminijail[7526]: blocked syscall: sched_getparam ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ /system/bin/tombstoned: received crash request for pid 7526 Although this CL cannot handle that extreme failure mode, it handles an error return from pthread_getschedparam() and won't use the uninitialized param.sched_priority value in that case. PiperOrigin-RevId: 247999953 -- bb154a92be37987d00d652c7c792594f2f515d83 by Abseil Team <absl-team@google.com>: Allow intrinsic int128 to be set for __aarch64__ targets. PiperOrigin-RevId: 247977594 GitOrigin-RevId: 22fceefcf070a0cf89bf1846bee16a9d36ad4161 Change-Id: I1f7ccfd82eb71446277a8e6f542fe835ac173d71
6 years ago
const int err = pthread_getschedparam(pthread_self(), &policy, &param);
if (err != 0) {
ABSL_RAW_LOG(ERROR, "pthread_getschedparam failed: %d", err);
} else {
s->priority = param.sched_priority;
s->next_priority_read_cycles =
now_cycles +
static_cast<int64_t>(base_internal::CycleClock::Frequency());
}
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}
if (s->priority > head->priority) { // s's priority is above head's
// try to put s in priority-fifo order, or failing that at the front.
if (!head->maybe_unlocking) {
// No unlocker can be scanning the queue, so we can insert between
// skip-chains, and within a skip-chain if it has the same condition as
// s. We insert in priority-fifo order, examining the end of every
// skip-chain, plus every element with the same condition as s.
PerThreadSynch *advance_to = head; // next value of enqueue_after
PerThreadSynch *cur; // successor of enqueue_after
do {
enqueue_after = advance_to;
cur = enqueue_after->next; // this advance ensures progress
advance_to = Skip(cur); // normally, advance to end of skip chain
// (side-effect: optimizes skip chain)
if (advance_to != cur && s->priority > advance_to->priority &&
MuSameCondition(s, cur)) {
// but this skip chain is not a singleton, s has higher priority
// than its tail and has the same condition as the chain,
// so we can insert within the skip-chain
advance_to = cur; // advance by just one
}
} while (s->priority <= advance_to->priority);
// termination guaranteed because s->priority > head->priority
// and head is the end of a skip chain
} else if (waitp->how == kExclusive &&
Condition::GuaranteedEqual(waitp->cond, nullptr)) {
// An unlocker could be scanning the queue, but we know it will recheck
// the queue front for writers that have no condition, which is what s
// is, so an insert at front is safe.
enqueue_after = head; // add after head, at front
}
}
#endif
if (enqueue_after != nullptr) {
s->next = enqueue_after->next;
enqueue_after->next = s;
// enqueue_after can be: head, Skip(...), or cur.
// The first two imply enqueue_after->skip == nullptr, and
// the last is used only if MuSameCondition(s, cur).
// We require this because clearing enqueue_after->skip
// is impossible; enqueue_after's predecessors might also
// incorrectly skip over s if we were to allow other
// insertion points.
ABSL_RAW_CHECK(
enqueue_after->skip == nullptr || MuSameCondition(enqueue_after, s),
"Mutex Enqueue failure");
if (enqueue_after != head && enqueue_after->may_skip &&
MuSameCondition(enqueue_after, enqueue_after->next)) {
// enqueue_after can skip to its new successor, s
enqueue_after->skip = enqueue_after->next;
}
if (MuSameCondition(s, s->next)) { // s->may_skip is known to be true
s->skip = s->next; // s may skip to its successor
}
} else { // enqueue not done any other way, so
// we're inserting s at the back
// s will become new head; copy data from head into it
s->next = head->next; // add s after head
head->next = s;
s->readers = head->readers; // reader count is from previous head
s->maybe_unlocking = head->maybe_unlocking; // same for unlock hint
if (head->may_skip && MuSameCondition(head, s)) {
// head now has successor; may skip
head->skip = s;
}
head = s; // s is new head
}
}
s->state.store(PerThreadSynch::kQueued, std::memory_order_relaxed);
return head;
}
// Dequeue the successor pw->next of thread pw from the Mutex waiter queue
// whose last element is head. The new head element is returned, or null
// if the list is made empty.
// Dequeue is called with both spinlock and Mutex held.
static PerThreadSynch *Dequeue(PerThreadSynch *head, PerThreadSynch *pw) {
PerThreadSynch *w = pw->next;
pw->next = w->next; // snip w out of list
if (head == w) { // we removed the head
head = (pw == w) ? nullptr : pw; // either emptied list, or pw is new head
} else if (pw != head && MuSameCondition(pw, pw->next)) {
// pw can skip to its new successor
if (pw->next->skip !=
nullptr) { // either skip to its successors skip target
pw->skip = pw->next->skip;
} else { // or to pw's successor
pw->skip = pw->next;
}
}
return head;
}
// Traverse the elements [ pw->next, h] of the circular list whose last element
// is head.
// Remove all elements with wake==true and place them in the
// singly-linked list wake_list in the order found. Assumes that
// there is only one such element if the element has how == kExclusive.
// Return the new head.
static PerThreadSynch *DequeueAllWakeable(PerThreadSynch *head,
PerThreadSynch *pw,
PerThreadSynch **wake_tail) {
PerThreadSynch *orig_h = head;
PerThreadSynch *w = pw->next;
bool skipped = false;
do {
if (w->wake) { // remove this element
ABSL_RAW_CHECK(pw->skip == nullptr, "bad skip in DequeueAllWakeable");
// we're removing pw's successor so either pw->skip is zero or we should
// already have removed pw since if pw->skip!=null, pw has the same
// condition as w.
head = Dequeue(head, pw);
w->next = *wake_tail; // keep list terminated
*wake_tail = w; // add w to wake_list;
wake_tail = &w->next; // next addition to end
if (w->waitp->how == kExclusive) { // wake at most 1 writer
break;
}
} else { // not waking this one; skip
pw = Skip(w); // skip as much as possible
skipped = true;
}
w = pw->next;
// We want to stop processing after we've considered the original head,
// orig_h. We can't test for w==orig_h in the loop because w may skip over
// it; we are guaranteed only that w's predecessor will not skip over
// orig_h. When we've considered orig_h, either we've processed it and
// removed it (so orig_h != head), or we considered it and skipped it (so
// skipped==true && pw == head because skipping from head always skips by
// just one, leaving pw pointing at head). So we want to
// continue the loop with the negation of that expression.
} while (orig_h == head && (pw != head || !skipped));
return head;
}
// Try to remove thread s from the list of waiters on this mutex.
// Does nothing if s is not on the waiter list.
void Mutex::TryRemove(PerThreadSynch *s) {
intptr_t v = mu_.load(std::memory_order_relaxed);
// acquire spinlock & lock
if ((v & (kMuWait | kMuSpin | kMuWriter | kMuReader)) == kMuWait &&
mu_.compare_exchange_strong(v, v | kMuSpin | kMuWriter,
std::memory_order_acquire,
std::memory_order_relaxed)) {
PerThreadSynch *h = GetPerThreadSynch(v);
if (h != nullptr) {
PerThreadSynch *pw = h; // pw is w's predecessor
PerThreadSynch *w;
if ((w = pw->next) != s) { // search for thread,
do { // processing at least one element
if (!MuSameCondition(s, w)) { // seeking different condition
pw = Skip(w); // so skip all that won't match
// we don't have to worry about dangling skip fields
// in the threads we skipped; none can point to s
// because their condition differs from s
} else { // seeking same condition
FixSkip(w, s); // fix up any skip pointer from w to s
pw = w;
}
// don't search further if we found the thread, or we're about to
// process the first thread again.
} while ((w = pw->next) != s && pw != h);
}
if (w == s) { // found thread; remove it
// pw->skip may be non-zero here; the loop above ensured that
// no ancestor of s can skip to s, so removal is safe anyway.
h = Dequeue(h, pw);
s->next = nullptr;
s->state.store(PerThreadSynch::kAvailable, std::memory_order_release);
}
}
intptr_t nv;
do { // release spinlock and lock
v = mu_.load(std::memory_order_relaxed);
nv = v & (kMuDesig | kMuEvent);
if (h != nullptr) {
nv |= kMuWait | reinterpret_cast<intptr_t>(h);
h->readers = 0; // we hold writer lock
h->maybe_unlocking = false; // finished unlocking
}
} while (!mu_.compare_exchange_weak(v, nv,
std::memory_order_release,
std::memory_order_relaxed));
}
}
// Wait until thread "s", which must be the current thread, is removed from the
// this mutex's waiter queue. If "s->waitp->timeout" has a timeout, wake up
// if the wait extends past the absolute time specified, even if "s" is still
// on the mutex queue. In this case, remove "s" from the queue and return
// true, otherwise return false.
ABSL_XRAY_LOG_ARGS(1) void Mutex::Block(PerThreadSynch *s) {
7 years ago
while (s->state.load(std::memory_order_acquire) == PerThreadSynch::kQueued) {
if (!DecrementSynchSem(this, s, s->waitp->timeout)) {
// After a timeout, we go into a spin loop until we remove ourselves
// from the queue, or someone else removes us. We can't be sure to be
// able to remove ourselves in a single lock acquisition because this
// mutex may be held, and the holder has the right to read the centre
// of the waiter queue without holding the spinlock.
this->TryRemove(s);
int c = 0;
while (s->next != nullptr) {
c = Delay(c, GENTLE);
this->TryRemove(s);
}
if (kDebugMode) {
// This ensures that we test the case that TryRemove() is called when s
// is not on the queue.
this->TryRemove(s);
}
s->waitp->timeout = KernelTimeout::Never(); // timeout is satisfied
s->waitp->cond = nullptr; // condition no longer relevant for wakeups
}
}
ABSL_RAW_CHECK(s->waitp != nullptr || s->suppress_fatal_errors,
"detected illegal recursion in Mutex code");
s->waitp = nullptr;
}
// Wake thread w, and return the next thread in the list.
PerThreadSynch *Mutex::Wakeup(PerThreadSynch *w) {
PerThreadSynch *next = w->next;
w->next = nullptr;
w->state.store(PerThreadSynch::kAvailable, std::memory_order_release);
IncrementSynchSem(this, w);
return next;
}
static GraphId GetGraphIdLocked(Mutex *mu)
ABSL_EXCLUSIVE_LOCKS_REQUIRED(deadlock_graph_mu) {
7 years ago
if (!deadlock_graph) { // (re)create the deadlock graph.
deadlock_graph =
new (base_internal::LowLevelAlloc::Alloc(sizeof(*deadlock_graph)))
GraphCycles;
}
return deadlock_graph->GetId(mu);
}
static GraphId GetGraphId(Mutex *mu) ABSL_LOCKS_EXCLUDED(deadlock_graph_mu) {
7 years ago
deadlock_graph_mu.Lock();
GraphId id = GetGraphIdLocked(mu);
deadlock_graph_mu.Unlock();
return id;
}
// Record a lock acquisition. This is used in debug mode for deadlock
// detection. The held_locks pointer points to the relevant data
// structure for each case.
static void LockEnter(Mutex* mu, GraphId id, SynchLocksHeld *held_locks) {
int n = held_locks->n;
int i = 0;
while (i != n && held_locks->locks[i].id != id) {
i++;
}
if (i == n) {
if (n == ABSL_ARRAYSIZE(held_locks->locks)) {
held_locks->overflow = true; // lost some data
} else { // we have room for lock
held_locks->locks[i].mu = mu;
held_locks->locks[i].count = 1;
held_locks->locks[i].id = id;
held_locks->n = n + 1;
}
} else {
held_locks->locks[i].count++;
}
}
// Record a lock release. Each call to LockEnter(mu, id, x) should be
// eventually followed by a call to LockLeave(mu, id, x) by the same thread.
// It does not process the event if is not needed when deadlock detection is
// disabled.
static void LockLeave(Mutex* mu, GraphId id, SynchLocksHeld *held_locks) {
int n = held_locks->n;
int i = 0;
while (i != n && held_locks->locks[i].id != id) {
i++;
}
if (i == n) {
if (!held_locks->overflow) {
// The deadlock id may have been reassigned after ForgetDeadlockInfo,
// but in that case mu should still be present.
i = 0;
while (i != n && held_locks->locks[i].mu != mu) {
i++;
}
if (i == n) { // mu missing means releasing unheld lock
SynchEvent *mu_events = GetSynchEvent(mu);
ABSL_RAW_LOG(FATAL,
"thread releasing lock it does not hold: %p %s; "
,
static_cast<void *>(mu),
mu_events == nullptr ? "" : mu_events->name);
}
}
} else if (held_locks->locks[i].count == 1) {
held_locks->n = n - 1;
held_locks->locks[i] = held_locks->locks[n - 1];
held_locks->locks[n - 1].id = InvalidGraphId();
held_locks->locks[n - 1].mu =
nullptr; // clear mu to please the leak detector.
} else {
assert(held_locks->locks[i].count > 0);
held_locks->locks[i].count--;
}
}
// Call LockEnter() if in debug mode and deadlock detection is enabled.
static inline void DebugOnlyLockEnter(Mutex *mu) {
if (kDebugMode) {
if (synch_deadlock_detection.load(std::memory_order_acquire) !=
OnDeadlockCycle::kIgnore) {
LockEnter(mu, GetGraphId(mu), Synch_GetAllLocks());
}
}
}
// Call LockEnter() if in debug mode and deadlock detection is enabled.
static inline void DebugOnlyLockEnter(Mutex *mu, GraphId id) {
if (kDebugMode) {
if (synch_deadlock_detection.load(std::memory_order_acquire) !=
OnDeadlockCycle::kIgnore) {
LockEnter(mu, id, Synch_GetAllLocks());
}
}
}
// Call LockLeave() if in debug mode and deadlock detection is enabled.
static inline void DebugOnlyLockLeave(Mutex *mu) {
if (kDebugMode) {
if (synch_deadlock_detection.load(std::memory_order_acquire) !=
OnDeadlockCycle::kIgnore) {
LockLeave(mu, GetGraphId(mu), Synch_GetAllLocks());
}
}
}
static char *StackString(void **pcs, int n, char *buf, int maxlen,
bool symbolize) {
static const int kSymLen = 200;
char sym[kSymLen];
int len = 0;
for (int i = 0; i != n; i++) {
if (symbolize) {
if (!symbolizer(pcs[i], sym, kSymLen)) {
sym[0] = '\0';
}
snprintf(buf + len, maxlen - len, "%s\t@ %p %s\n",
(i == 0 ? "\n" : ""),
pcs[i], sym);
} else {
snprintf(buf + len, maxlen - len, " %p", pcs[i]);
}
len += strlen(&buf[len]);
}
return buf;
}
static char *CurrentStackString(char *buf, int maxlen, bool symbolize) {
void *pcs[40];
return StackString(pcs, absl::GetStackTrace(pcs, ABSL_ARRAYSIZE(pcs), 2), buf,
maxlen, symbolize);
}
namespace {
enum { kMaxDeadlockPathLen = 10 }; // maximum length of a deadlock cycle;
// a path this long would be remarkable
// Buffers required to report a deadlock.
// We do not allocate them on stack to avoid large stack frame.
struct DeadlockReportBuffers {
char buf[6100];
GraphId path[kMaxDeadlockPathLen];
};
struct ScopedDeadlockReportBuffers {
ScopedDeadlockReportBuffers() {
b = reinterpret_cast<DeadlockReportBuffers *>(
base_internal::LowLevelAlloc::Alloc(sizeof(*b)));
}
~ScopedDeadlockReportBuffers() { base_internal::LowLevelAlloc::Free(b); }
DeadlockReportBuffers *b;
};
// Helper to pass to GraphCycles::UpdateStackTrace.
int GetStack(void** stack, int max_depth) {
return absl::GetStackTrace(stack, max_depth, 3);
}
} // anonymous namespace
// Called in debug mode when a thread is about to acquire a lock in a way that
// may block.
static GraphId DeadlockCheck(Mutex *mu) {
if (synch_deadlock_detection.load(std::memory_order_acquire) ==
OnDeadlockCycle::kIgnore) {
return InvalidGraphId();
}
SynchLocksHeld *all_locks = Synch_GetAllLocks();
absl::base_internal::SpinLockHolder lock(&deadlock_graph_mu);
const GraphId mu_id = GetGraphIdLocked(mu);
if (all_locks->n == 0) {
// There are no other locks held. Return now so that we don't need to
// call GetSynchEvent(). This way we do not record the stack trace
// for this Mutex. It's ok, since if this Mutex is involved in a deadlock,
// it can't always be the first lock acquired by a thread.
return mu_id;
}
// We prefer to keep stack traces that show a thread holding and acquiring
// as many locks as possible. This increases the chances that a given edge
// in the acquires-before graph will be represented in the stack traces
// recorded for the locks.
deadlock_graph->UpdateStackTrace(mu_id, all_locks->n + 1, GetStack);
// For each other mutex already held by this thread:
for (int i = 0; i != all_locks->n; i++) {
const GraphId other_node_id = all_locks->locks[i].id;
const Mutex *other =
static_cast<const Mutex *>(deadlock_graph->Ptr(other_node_id));
if (other == nullptr) {
// Ignore stale lock
continue;
}
// Add the acquired-before edge to the graph.
if (!deadlock_graph->InsertEdge(other_node_id, mu_id)) {
ScopedDeadlockReportBuffers scoped_buffers;
DeadlockReportBuffers *b = scoped_buffers.b;
static int number_of_reported_deadlocks = 0;
number_of_reported_deadlocks++;
// Symbolize only 2 first deadlock report to avoid huge slowdowns.
bool symbolize = number_of_reported_deadlocks <= 2;
ABSL_RAW_LOG(ERROR, "Potential Mutex deadlock: %s",
CurrentStackString(b->buf, sizeof (b->buf), symbolize));
int len = 0;
for (int j = 0; j != all_locks->n; j++) {
void* pr = deadlock_graph->Ptr(all_locks->locks[j].id);
if (pr != nullptr) {
snprintf(b->buf + len, sizeof (b->buf) - len, " %p", pr);
len += static_cast<int>(strlen(&b->buf[len]));
}
}
ABSL_RAW_LOG(ERROR, "Acquiring %p Mutexes held: %s",
static_cast<void *>(mu), b->buf);
ABSL_RAW_LOG(ERROR, "Cycle: ");
int path_len = deadlock_graph->FindPath(
mu_id, other_node_id, ABSL_ARRAYSIZE(b->path), b->path);
for (int j = 0; j != path_len; j++) {
GraphId id = b->path[j];
Mutex *path_mu = static_cast<Mutex *>(deadlock_graph->Ptr(id));
if (path_mu == nullptr) continue;
void** stack;
int depth = deadlock_graph->GetStackTrace(id, &stack);
snprintf(b->buf, sizeof(b->buf),
"mutex@%p stack: ", static_cast<void *>(path_mu));
StackString(stack, depth, b->buf + strlen(b->buf),
static_cast<int>(sizeof(b->buf) - strlen(b->buf)),
symbolize);
ABSL_RAW_LOG(ERROR, "%s", b->buf);
}
if (synch_deadlock_detection.load(std::memory_order_acquire) ==
OnDeadlockCycle::kAbort) {
deadlock_graph_mu.Unlock(); // avoid deadlock in fatal sighandler
ABSL_RAW_LOG(FATAL, "dying due to potential deadlock");
return mu_id;
}
break; // report at most one potential deadlock per acquisition
}
}
return mu_id;
}
// Invoke DeadlockCheck() iff we're in debug mode and
// deadlock checking has been enabled.
static inline GraphId DebugOnlyDeadlockCheck(Mutex *mu) {
if (kDebugMode && synch_deadlock_detection.load(std::memory_order_acquire) !=
OnDeadlockCycle::kIgnore) {
return DeadlockCheck(mu);
} else {
return InvalidGraphId();
}
}
void Mutex::ForgetDeadlockInfo() {
if (kDebugMode && synch_deadlock_detection.load(std::memory_order_acquire) !=
OnDeadlockCycle::kIgnore) {
deadlock_graph_mu.Lock();
if (deadlock_graph != nullptr) {
deadlock_graph->RemoveNode(this);
}
deadlock_graph_mu.Unlock();
}
}
void Mutex::AssertNotHeld() const {
// We have the data to allow this check only if in debug mode and deadlock
// detection is enabled.
if (kDebugMode &&
(mu_.load(std::memory_order_relaxed) & (kMuWriter | kMuReader)) != 0 &&
synch_deadlock_detection.load(std::memory_order_acquire) !=
OnDeadlockCycle::kIgnore) {
GraphId id = GetGraphId(const_cast<Mutex *>(this));
SynchLocksHeld *locks = Synch_GetAllLocks();
for (int i = 0; i != locks->n; i++) {
if (locks->locks[i].id == id) {
SynchEvent *mu_events = GetSynchEvent(this);
ABSL_RAW_LOG(FATAL, "thread should not hold mutex %p %s",
static_cast<const void *>(this),
(mu_events == nullptr ? "" : mu_events->name));
}
}
}
}
// Attempt to acquire *mu, and return whether successful. The implementation
// may spin for a short while if the lock cannot be acquired immediately.
static bool TryAcquireWithSpinning(std::atomic<intptr_t>* mu) {
int c = mutex_globals.spinloop_iterations;
int result = -1; // result of operation: 0=false, 1=true, -1=unknown
do { // do/while somewhat faster on AMD
intptr_t v = mu->load(std::memory_order_relaxed);
if ((v & (kMuReader|kMuEvent)) != 0) { // a reader or tracing -> give up
result = 0;
} else if (((v & kMuWriter) == 0) && // no holder -> try to acquire
mu->compare_exchange_strong(v, kMuWriter | v,
std::memory_order_acquire,
std::memory_order_relaxed)) {
result = 1;
}
} while (result == -1 && --c > 0);
return result == 1;
}
ABSL_XRAY_LOG_ARGS(1) void Mutex::Lock() {
ABSL_TSAN_MUTEX_PRE_LOCK(this, 0);
GraphId id = DebugOnlyDeadlockCheck(this);
intptr_t v = mu_.load(std::memory_order_relaxed);
// try fast acquire, then spin loop
if ((v & (kMuWriter | kMuReader | kMuEvent)) != 0 ||
!mu_.compare_exchange_strong(v, kMuWriter | v,
std::memory_order_acquire,
std::memory_order_relaxed)) {
// try spin acquire, then slow loop
if (!TryAcquireWithSpinning(&this->mu_)) {
this->LockSlow(kExclusive, nullptr, 0);
}
}
DebugOnlyLockEnter(this, id);
ABSL_TSAN_MUTEX_POST_LOCK(this, 0, 0);
}
ABSL_XRAY_LOG_ARGS(1) void Mutex::ReaderLock() {
ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_read_lock);
GraphId id = DebugOnlyDeadlockCheck(this);
intptr_t v = mu_.load(std::memory_order_relaxed);
// try fast acquire, then slow loop
if ((v & (kMuWriter | kMuWait | kMuEvent)) != 0 ||
!mu_.compare_exchange_strong(v, (kMuReader | v) + kMuOne,
std::memory_order_acquire,
std::memory_order_relaxed)) {
this->LockSlow(kShared, nullptr, 0);
}
DebugOnlyLockEnter(this, id);
ABSL_TSAN_MUTEX_POST_LOCK(this, __tsan_mutex_read_lock, 0);
}
void Mutex::LockWhen(const Condition &cond) {
ABSL_TSAN_MUTEX_PRE_LOCK(this, 0);
GraphId id = DebugOnlyDeadlockCheck(this);
this->LockSlow(kExclusive, &cond, 0);
DebugOnlyLockEnter(this, id);
ABSL_TSAN_MUTEX_POST_LOCK(this, 0, 0);
}
bool Mutex::LockWhenWithTimeout(const Condition &cond, absl::Duration timeout) {
return LockWhenWithDeadline(cond, DeadlineFromTimeout(timeout));
}
bool Mutex::LockWhenWithDeadline(const Condition &cond, absl::Time deadline) {
ABSL_TSAN_MUTEX_PRE_LOCK(this, 0);
GraphId id = DebugOnlyDeadlockCheck(this);
bool res = LockSlowWithDeadline(kExclusive, &cond,
KernelTimeout(deadline), 0);
DebugOnlyLockEnter(this, id);
ABSL_TSAN_MUTEX_POST_LOCK(this, 0, 0);
return res;
}
void Mutex::ReaderLockWhen(const Condition &cond) {
ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_read_lock);
GraphId id = DebugOnlyDeadlockCheck(this);
this->LockSlow(kShared, &cond, 0);
DebugOnlyLockEnter(this, id);
ABSL_TSAN_MUTEX_POST_LOCK(this, __tsan_mutex_read_lock, 0);
}
bool Mutex::ReaderLockWhenWithTimeout(const Condition &cond,
absl::Duration timeout) {
return ReaderLockWhenWithDeadline(cond, DeadlineFromTimeout(timeout));
}
bool Mutex::ReaderLockWhenWithDeadline(const Condition &cond,
absl::Time deadline) {
ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_read_lock);
GraphId id = DebugOnlyDeadlockCheck(this);
bool res = LockSlowWithDeadline(kShared, &cond, KernelTimeout(deadline), 0);
DebugOnlyLockEnter(this, id);
ABSL_TSAN_MUTEX_POST_LOCK(this, __tsan_mutex_read_lock, 0);
return res;
}
void Mutex::Await(const Condition &cond) {
if (cond.Eval()) { // condition already true; nothing to do
if (kDebugMode) {
this->AssertReaderHeld();
}
} else { // normal case
ABSL_RAW_CHECK(this->AwaitCommon(cond, KernelTimeout::Never()),
"condition untrue on return from Await");
}
}
bool Mutex::AwaitWithTimeout(const Condition &cond, absl::Duration timeout) {
return AwaitWithDeadline(cond, DeadlineFromTimeout(timeout));
}
bool Mutex::AwaitWithDeadline(const Condition &cond, absl::Time deadline) {
if (cond.Eval()) { // condition already true; nothing to do
if (kDebugMode) {
this->AssertReaderHeld();
}
return true;
}
KernelTimeout t{deadline};
bool res = this->AwaitCommon(cond, t);
ABSL_RAW_CHECK(res || t.has_timeout(),
"condition untrue on return from Await");
return res;
}
bool Mutex::AwaitCommon(const Condition &cond, KernelTimeout t) {
this->AssertReaderHeld();
MuHow how =
(mu_.load(std::memory_order_relaxed) & kMuWriter) ? kExclusive : kShared;
ABSL_TSAN_MUTEX_PRE_UNLOCK(this, TsanFlags(how));
SynchWaitParams waitp(
how, &cond, t, nullptr /*no cvmu*/, Synch_GetPerThreadAnnotated(this),
nullptr /*no cv_word*/);
int flags = kMuHasBlocked;
if (!Condition::GuaranteedEqual(&cond, nullptr)) {
flags |= kMuIsCond;
}
this->UnlockSlow(&waitp);
this->Block(waitp.thread);
ABSL_TSAN_MUTEX_POST_UNLOCK(this, TsanFlags(how));
ABSL_TSAN_MUTEX_PRE_LOCK(this, TsanFlags(how));
this->LockSlowLoop(&waitp, flags);
bool res = waitp.cond != nullptr || // => cond known true from LockSlowLoop
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
EvalConditionAnnotated(&cond, this, true, false, how == kShared);
7 years ago
ABSL_TSAN_MUTEX_POST_LOCK(this, TsanFlags(how), 0);
return res;
}
ABSL_XRAY_LOG_ARGS(1) bool Mutex::TryLock() {
ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_try_lock);
intptr_t v = mu_.load(std::memory_order_relaxed);
if ((v & (kMuWriter | kMuReader | kMuEvent)) == 0 && // try fast acquire
mu_.compare_exchange_strong(v, kMuWriter | v,
std::memory_order_acquire,
std::memory_order_relaxed)) {
DebugOnlyLockEnter(this);
ABSL_TSAN_MUTEX_POST_LOCK(this, __tsan_mutex_try_lock, 0);
return true;
}
if ((v & kMuEvent) != 0) { // we're recording events
if ((v & kExclusive->slow_need_zero) == 0 && // try fast acquire
mu_.compare_exchange_strong(
v, (kExclusive->fast_or | v) + kExclusive->fast_add,
std::memory_order_acquire, std::memory_order_relaxed)) {
DebugOnlyLockEnter(this);
PostSynchEvent(this, SYNCH_EV_TRYLOCK_SUCCESS);
ABSL_TSAN_MUTEX_POST_LOCK(this, __tsan_mutex_try_lock, 0);
return true;
} else {
PostSynchEvent(this, SYNCH_EV_TRYLOCK_FAILED);
}
}
ABSL_TSAN_MUTEX_POST_LOCK(
this, __tsan_mutex_try_lock | __tsan_mutex_try_lock_failed, 0);
return false;
}
ABSL_XRAY_LOG_ARGS(1) bool Mutex::ReaderTryLock() {
ABSL_TSAN_MUTEX_PRE_LOCK(this,
__tsan_mutex_read_lock | __tsan_mutex_try_lock);
intptr_t v = mu_.load(std::memory_order_relaxed);
// The while-loops (here and below) iterate only if the mutex word keeps
// changing (typically because the reader count changes) under the CAS. We
// limit the number of attempts to avoid having to think about livelock.
int loop_limit = 5;
while ((v & (kMuWriter|kMuWait|kMuEvent)) == 0 && loop_limit != 0) {
if (mu_.compare_exchange_strong(v, (kMuReader | v) + kMuOne,
std::memory_order_acquire,
std::memory_order_relaxed)) {
DebugOnlyLockEnter(this);
ABSL_TSAN_MUTEX_POST_LOCK(
this, __tsan_mutex_read_lock | __tsan_mutex_try_lock, 0);
return true;
}
loop_limit--;
v = mu_.load(std::memory_order_relaxed);
}
if ((v & kMuEvent) != 0) { // we're recording events
loop_limit = 5;
while ((v & kShared->slow_need_zero) == 0 && loop_limit != 0) {
if (mu_.compare_exchange_strong(v, (kMuReader | v) + kMuOne,
std::memory_order_acquire,
std::memory_order_relaxed)) {
DebugOnlyLockEnter(this);
PostSynchEvent(this, SYNCH_EV_READERTRYLOCK_SUCCESS);
ABSL_TSAN_MUTEX_POST_LOCK(
this, __tsan_mutex_read_lock | __tsan_mutex_try_lock, 0);
return true;
}
loop_limit--;
v = mu_.load(std::memory_order_relaxed);
}
if ((v & kMuEvent) != 0) {
PostSynchEvent(this, SYNCH_EV_READERTRYLOCK_FAILED);
}
}
ABSL_TSAN_MUTEX_POST_LOCK(this,
__tsan_mutex_read_lock | __tsan_mutex_try_lock |
__tsan_mutex_try_lock_failed,
0);
return false;
}
ABSL_XRAY_LOG_ARGS(1) void Mutex::Unlock() {
ABSL_TSAN_MUTEX_PRE_UNLOCK(this, 0);
DebugOnlyLockLeave(this);
intptr_t v = mu_.load(std::memory_order_relaxed);
if (kDebugMode && ((v & (kMuWriter | kMuReader)) != kMuWriter)) {
ABSL_RAW_LOG(FATAL, "Mutex unlocked when destroyed or not locked: v=0x%x",
static_cast<unsigned>(v));
}
// should_try_cas is whether we'll try a compare-and-swap immediately.
// NOTE: optimized out when kDebugMode is false.
bool should_try_cas = ((v & (kMuEvent | kMuWriter)) == kMuWriter &&
(v & (kMuWait | kMuDesig)) != kMuWait);
// But, we can use an alternate computation of it, that compilers
// currently don't find on their own. When that changes, this function
// can be simplified.
intptr_t x = (v ^ (kMuWriter | kMuWait)) & (kMuWriter | kMuEvent);
intptr_t y = (v ^ (kMuWriter | kMuWait)) & (kMuWait | kMuDesig);
// Claim: "x == 0 && y > 0" is equal to should_try_cas.
// Also, because kMuWriter and kMuEvent exceed kMuDesig and kMuWait,
// all possible non-zero values for x exceed all possible values for y.
// Therefore, (x == 0 && y > 0) == (x < y).
if (kDebugMode && should_try_cas != (x < y)) {
// We would usually use PRIdPTR here, but is not correctly implemented
// within the android toolchain.
ABSL_RAW_LOG(FATAL, "internal logic error %llx %llx %llx\n",
static_cast<long long>(v), static_cast<long long>(x),
static_cast<long long>(y));
}
if (x < y &&
mu_.compare_exchange_strong(v, v & ~(kMuWrWait | kMuWriter),
std::memory_order_release,
std::memory_order_relaxed)) {
// fast writer release (writer with no waiters or with designated waker)
} else {
this->UnlockSlow(nullptr /*no waitp*/); // take slow path
}
ABSL_TSAN_MUTEX_POST_UNLOCK(this, 0);
}
// Requires v to represent a reader-locked state.
static bool ExactlyOneReader(intptr_t v) {
assert((v & (kMuWriter|kMuReader)) == kMuReader);
assert((v & kMuHigh) != 0);
// The more straightforward "(v & kMuHigh) == kMuOne" also works, but
// on some architectures the following generates slightly smaller code.
// It may be faster too.
constexpr intptr_t kMuMultipleWaitersMask = kMuHigh ^ kMuOne;
return (v & kMuMultipleWaitersMask) == 0;
}
ABSL_XRAY_LOG_ARGS(1) void Mutex::ReaderUnlock() {
ABSL_TSAN_MUTEX_PRE_UNLOCK(this, __tsan_mutex_read_lock);
DebugOnlyLockLeave(this);
intptr_t v = mu_.load(std::memory_order_relaxed);
assert((v & (kMuWriter|kMuReader)) == kMuReader);
if ((v & (kMuReader|kMuWait|kMuEvent)) == kMuReader) {
// fast reader release (reader with no waiters)
intptr_t clear = ExactlyOneReader(v) ? kMuReader|kMuOne : kMuOne;
if (mu_.compare_exchange_strong(v, v - clear,
std::memory_order_release,
std::memory_order_relaxed)) {
ABSL_TSAN_MUTEX_POST_UNLOCK(this, __tsan_mutex_read_lock);
return;
}
}
this->UnlockSlow(nullptr /*no waitp*/); // take slow path
ABSL_TSAN_MUTEX_POST_UNLOCK(this, __tsan_mutex_read_lock);
}
// The zap_desig_waker bitmask is used to clear the designated waker flag in
// the mutex if this thread has blocked, and therefore may be the designated
// waker.
static const intptr_t zap_desig_waker[] = {
~static_cast<intptr_t>(0), // not blocked
~static_cast<intptr_t>(
kMuDesig) // blocked; turn off the designated waker bit
};
// The ignore_waiting_writers bitmask is used to ignore the existence
// of waiting writers if a reader that has already blocked once
// wakes up.
static const intptr_t ignore_waiting_writers[] = {
~static_cast<intptr_t>(0), // not blocked
~static_cast<intptr_t>(
kMuWrWait) // blocked; pretend there are no waiting writers
};
// Internal version of LockWhen(). See LockSlowWithDeadline()
void Mutex::LockSlow(MuHow how, const Condition *cond, int flags) {
ABSL_RAW_CHECK(
this->LockSlowWithDeadline(how, cond, KernelTimeout::Never(), flags),
"condition untrue on return from LockSlow");
}
// Compute cond->Eval() and tell race detectors that we do it under mutex mu.
static inline bool EvalConditionAnnotated(const Condition *cond, Mutex *mu,
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
bool locking, bool trylock,
bool read_lock) {
7 years ago
// Delicate annotation dance.
// We are currently inside of read/write lock/unlock operation.
// All memory accesses are ignored inside of mutex operations + for unlock
// operation tsan considers that we've already released the mutex.
bool res = false;
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
#ifdef THREAD_SANITIZER
const int flags = read_lock ? __tsan_mutex_read_lock : 0;
const int tryflags = flags | (trylock ? __tsan_mutex_try_lock : 0);
#endif
7 years ago
if (locking) {
// For lock we pretend that we have finished the operation,
// evaluate the predicate, then unlock the mutex and start locking it again
// to match the annotation at the end of outer lock operation.
// Note: we can't simply do POST_LOCK, Eval, PRE_LOCK, because then tsan
// will think the lock acquisition is recursive which will trigger
// deadlock detector.
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
ABSL_TSAN_MUTEX_POST_LOCK(mu, tryflags, 0);
7 years ago
res = cond->Eval();
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
// There is no "try" version of Unlock, so use flags instead of tryflags.
ABSL_TSAN_MUTEX_PRE_UNLOCK(mu, flags);
ABSL_TSAN_MUTEX_POST_UNLOCK(mu, flags);
ABSL_TSAN_MUTEX_PRE_LOCK(mu, tryflags);
7 years ago
} else {
// Similarly, for unlock we pretend that we have unlocked the mutex,
// lock the mutex, evaluate the predicate, and start unlocking it again
// to match the annotation at the end of outer unlock operation.
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
ABSL_TSAN_MUTEX_POST_UNLOCK(mu, flags);
ABSL_TSAN_MUTEX_PRE_LOCK(mu, flags);
ABSL_TSAN_MUTEX_POST_LOCK(mu, flags, 0);
7 years ago
res = cond->Eval();
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
ABSL_TSAN_MUTEX_PRE_UNLOCK(mu, flags);
7 years ago
}
// Prevent unused param warnings in non-TSAN builds.
static_cast<void>(mu);
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
static_cast<void>(trylock);
static_cast<void>(read_lock);
7 years ago
return res;
}
// Compute cond->Eval() hiding it from race detectors.
// We are hiding it because inside of UnlockSlow we can evaluate a predicate
// that was just added by a concurrent Lock operation; Lock adds the predicate
// to the internal Mutex list without actually acquiring the Mutex
// (it only acquires the internal spinlock, which is rightfully invisible for
// tsan). As the result there is no tsan-visible synchronization between the
// addition and this thread. So if we would enable race detection here,
// it would race with the predicate initialization.
static inline bool EvalConditionIgnored(Mutex *mu, const Condition *cond) {
// Memory accesses are already ignored inside of lock/unlock operations,
// but synchronization operations are also ignored. When we evaluate the
// predicate we must ignore only memory accesses but not synchronization,
// because missed synchronization can lead to false reports later.
// So we "divert" (which un-ignores both memory accesses and synchronization)
// and then separately turn on ignores of memory accesses.
ABSL_TSAN_MUTEX_PRE_DIVERT(mu, 0);
ANNOTATE_IGNORE_READS_AND_WRITES_BEGIN();
bool res = cond->Eval();
ANNOTATE_IGNORE_READS_AND_WRITES_END();
ABSL_TSAN_MUTEX_POST_DIVERT(mu, 0);
static_cast<void>(mu); // Prevent unused param warning in non-TSAN builds.
return res;
}
// Internal equivalent of *LockWhenWithDeadline(), where
// "t" represents the absolute timeout; !t.has_timeout() means "forever".
// "how" is "kShared" (for ReaderLockWhen) or "kExclusive" (for LockWhen)
// In flags, bits are ored together:
// - kMuHasBlocked indicates that the client has already blocked on the call so
// the designated waker bit must be cleared and waiting writers should not
// obstruct this call
// - kMuIsCond indicates that this is a conditional acquire (condition variable,
// Await, LockWhen) so contention profiling should be suppressed.
bool Mutex::LockSlowWithDeadline(MuHow how, const Condition *cond,
KernelTimeout t, int flags) {
intptr_t v = mu_.load(std::memory_order_relaxed);
bool unlock = false;
if ((v & how->fast_need_zero) == 0 && // try fast acquire
mu_.compare_exchange_strong(
v, (how->fast_or | (v & zap_desig_waker[flags & kMuHasBlocked])) +
how->fast_add,
std::memory_order_acquire, std::memory_order_relaxed)) {
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
if (cond == nullptr ||
EvalConditionAnnotated(cond, this, true, false, how == kShared)) {
7 years ago
return true;
}
unlock = true;
}
SynchWaitParams waitp(
how, cond, t, nullptr /*no cvmu*/, Synch_GetPerThreadAnnotated(this),
nullptr /*no cv_word*/);
if (!Condition::GuaranteedEqual(cond, nullptr)) {
flags |= kMuIsCond;
}
if (unlock) {
this->UnlockSlow(&waitp);
this->Block(waitp.thread);
flags |= kMuHasBlocked;
}
this->LockSlowLoop(&waitp, flags);
return waitp.cond != nullptr || // => cond known true from LockSlowLoop
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
cond == nullptr ||
EvalConditionAnnotated(cond, this, true, false, how == kShared);
7 years ago
}
// RAW_CHECK_FMT() takes a condition, a printf-style format string, and
// the printf-style argument list. The format string must be a literal.
7 years ago
// Arguments after the first are not evaluated unless the condition is true.
#define RAW_CHECK_FMT(cond, ...) \
do { \
if (ABSL_PREDICT_FALSE(!(cond))) { \
ABSL_RAW_LOG(FATAL, "Check " #cond " failed: " __VA_ARGS__); \
} \
} while (0)
static void CheckForMutexCorruption(intptr_t v, const char* label) {
// Test for either of two situations that should not occur in v:
// kMuWriter and kMuReader
// kMuWrWait and !kMuWait
const uintptr_t w = v ^ kMuWait;
7 years ago
// By flipping that bit, we can now test for:
// kMuWriter and kMuReader in w
// kMuWrWait and kMuWait in w
// We've chosen these two pairs of values to be so that they will overlap,
// respectively, when the word is left shifted by three. This allows us to
// save a branch in the common (correct) case of them not being coincident.
static_assert(kMuReader << 3 == kMuWriter, "must match");
static_assert(kMuWait << 3 == kMuWrWait, "must match");
if (ABSL_PREDICT_TRUE((w & (w << 3) & (kMuWriter | kMuWrWait)) == 0)) return;
RAW_CHECK_FMT((v & (kMuWriter | kMuReader)) != (kMuWriter | kMuReader),
"%s: Mutex corrupt: both reader and writer lock held: %p",
label, reinterpret_cast<void *>(v));
RAW_CHECK_FMT((v & (kMuWait | kMuWrWait)) != kMuWrWait,
"%s: Mutex corrupt: waiting writer with no waiters: %p",
label, reinterpret_cast<void *>(v));
assert(false);
}
void Mutex::LockSlowLoop(SynchWaitParams *waitp, int flags) {
int c = 0;
intptr_t v = mu_.load(std::memory_order_relaxed);
if ((v & kMuEvent) != 0) {
PostSynchEvent(this,
waitp->how == kExclusive? SYNCH_EV_LOCK: SYNCH_EV_READERLOCK);
}
ABSL_RAW_CHECK(
waitp->thread->waitp == nullptr || waitp->thread->suppress_fatal_errors,
"detected illegal recursion into Mutex code");
for (;;) {
v = mu_.load(std::memory_order_relaxed);
CheckForMutexCorruption(v, "Lock");
if ((v & waitp->how->slow_need_zero) == 0) {
if (mu_.compare_exchange_strong(
v, (waitp->how->fast_or |
(v & zap_desig_waker[flags & kMuHasBlocked])) +
waitp->how->fast_add,
std::memory_order_acquire, std::memory_order_relaxed)) {
if (waitp->cond == nullptr ||
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
EvalConditionAnnotated(waitp->cond, this, true, false,
waitp->how == kShared)) {
7 years ago
break; // we timed out, or condition true, so return
}
this->UnlockSlow(waitp); // got lock but condition false
this->Block(waitp->thread);
flags |= kMuHasBlocked;
c = 0;
}
} else { // need to access waiter list
bool dowait = false;
if ((v & (kMuSpin|kMuWait)) == 0) { // no waiters
// This thread tries to become the one and only waiter.
PerThreadSynch *new_h = Enqueue(nullptr, waitp, v, flags);
intptr_t nv = (v & zap_desig_waker[flags & kMuHasBlocked] & kMuLow) |
kMuWait;
ABSL_RAW_CHECK(new_h != nullptr, "Enqueue to empty list failed");
if (waitp->how == kExclusive && (v & kMuReader) != 0) {
nv |= kMuWrWait;
}
if (mu_.compare_exchange_strong(
v, reinterpret_cast<intptr_t>(new_h) | nv,
std::memory_order_release, std::memory_order_relaxed)) {
dowait = true;
} else { // attempted Enqueue() failed
// zero out the waitp field set by Enqueue()
waitp->thread->waitp = nullptr;
}
} else if ((v & waitp->how->slow_inc_need_zero &
ignore_waiting_writers[flags & kMuHasBlocked]) == 0) {
// This is a reader that needs to increment the reader count,
// but the count is currently held in the last waiter.
if (mu_.compare_exchange_strong(
v, (v & zap_desig_waker[flags & kMuHasBlocked]) | kMuSpin |
kMuReader,
std::memory_order_acquire, std::memory_order_relaxed)) {
PerThreadSynch *h = GetPerThreadSynch(v);
h->readers += kMuOne; // inc reader count in waiter
do { // release spinlock
v = mu_.load(std::memory_order_relaxed);
} while (!mu_.compare_exchange_weak(v, (v & ~kMuSpin) | kMuReader,
std::memory_order_release,
std::memory_order_relaxed));
if (waitp->cond == nullptr ||
Export of internal Abseil changes. -- 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d by Derek Mauro <dmauro@google.com>: Set correct flags for clang-cl. https://github.com/abseil/abseil-cpp/pull/278 clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases. clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC. clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]). clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC. CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it. We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel.. Other changes: Add ABSL_ prefix to variable names to avoid name collision in CMake. PiperOrigin-RevId: 239841297 -- add96c3fc067d5c7b6f016d2ba74725a443a185e by CJ Johnson <johnsoncj@google.com>: Eventually Storage will need to refer to the type `absl::InlinedVector<...>*`. This can be done via a forward declaration. However, doing so would move the defaulted allocator template parameter to the forward declaration and thus inside an internal file. Instead of doing that, this change gives Storage access to the template and it's parameters so the complete type can be formed without including it. PiperOrigin-RevId: 239811298 -- b5f5279f1b13b09cae5c745597d64ea1efab146b by CJ Johnson <johnsoncj@google.com>: Simplify/cleanup the benchmark tests for InlinedVector PiperOrigin-RevId: 239805767 -- f5991e51b43b13a0ae95025474071f5039a33d27 by Matt Calabrese <calabrese@google.com>: Update the internal-only IsSwappable traits to be nested inside of namespace absl so that the script to add inline namespaces for LTS releases works with the implementation. PiperOrigin-RevId: 239622024 -- d1cb234dc5706f033ad56f4eb16d94ac5da80d52 by Abseil Team <absl-team@google.com>: Mutex: fix tsan annotations This fixes 2 bugs: 1. We call cond directly in Mutex::AwaitCommon without using EvalConditionAnnotated. As the result we call into user code ignoring synchronization, miss synchronization and report false positives later. Use EvalConditionAnnotated to call cond as we should. 2. We call Mutex invariant ignoring synchronization. Result is the same: we miss synchronization and report false positive races later. Reuse EvalConditionAnnotated to call mutex invariant too. PiperOrigin-RevId: 239583878 -- 52295e4922a9b408fa0dd03d27bc91ccc6645cd7 by Abseil Team <absl-team@google.com>: Clarify how to obtain the same behavior as std::unordered_map::erase if need be. PiperOrigin-RevId: 239549513 -- 6e76e68ed084fd1247981dbb92677ce8e563b0ec by Jon Cohen <cohenjon@google.com>: Avoid the -S -B form of `cmake` since it's only supported starting in CMake 3.13 PiperOrigin-RevId: 239473143 GitOrigin-RevId: 8b7c3bc2fb69608e9b2389b1be0b0de840a4c59d Change-Id: Ib6d356fa1a7435260273df991e65df4149bd5861
6 years ago
EvalConditionAnnotated(waitp->cond, this, true, false,
waitp->how == kShared)) {
7 years ago
break; // we timed out, or condition true, so return
}
this->UnlockSlow(waitp); // got lock but condition false
this->Block(waitp->thread);
flags |= kMuHasBlocked;
c = 0;
}
} else if ((v & kMuSpin) == 0 && // attempt to queue ourselves
mu_.compare_exchange_strong(
v, (v & zap_desig_waker[flags & kMuHasBlocked]) | kMuSpin |
kMuWait,
std::memory_order_acquire, std::memory_order_relaxed)) {
PerThreadSynch *h = GetPerThreadSynch(v);
PerThreadSynch *new_h = Enqueue(h, waitp, v, flags);
intptr_t wr_wait = 0;
ABSL_RAW_CHECK(new_h != nullptr, "Enqueue to list failed");
if (waitp->how == kExclusive && (v & kMuReader) != 0) {
wr_wait = kMuWrWait; // give priority to a waiting writer
}
do { // release spinlock
v = mu_.load(std::memory_order_relaxed);
} while (!mu_.compare_exchange_weak(
v, (v & (kMuLow & ~kMuSpin)) | kMuWait | wr_wait |
reinterpret_cast<intptr_t>(new_h),
std::memory_order_release, std::memory_order_relaxed));
dowait = true;
}
if (dowait) {
this->Block(waitp->thread); // wait until removed from list or timeout
flags |= kMuHasBlocked;
c = 0;
}
}
ABSL_RAW_CHECK(
waitp->thread->waitp == nullptr || waitp->thread->suppress_fatal_errors,
"detected illegal recursion into Mutex code");
c = Delay(c, GENTLE); // delay, then try again
}
ABSL_RAW_CHECK(
waitp->thread->waitp == nullptr || waitp->thread->suppress_fatal_errors,
"detected illegal recursion into Mutex code");
if ((v & kMuEvent) != 0) {
PostSynchEvent(this,
waitp->how == kExclusive? SYNCH_EV_LOCK_RETURNING :
SYNCH_EV_READERLOCK_RETURNING);
}
}
// Unlock this mutex, which is held by the current thread.
// If waitp is non-zero, it must be the wait parameters for the current thread
// which holds the lock but is not runnable because its condition is false
// or it is in the process of blocking on a condition variable; it must requeue
7 years ago
// itself on the mutex/condvar to wait for its condition to become true.
void Mutex::UnlockSlow(SynchWaitParams *waitp) {
intptr_t v = mu_.load(std::memory_order_relaxed);
this->AssertReaderHeld();
CheckForMutexCorruption(v, "Unlock");
if ((v & kMuEvent) != 0) {
PostSynchEvent(this,
(v & kMuWriter) != 0? SYNCH_EV_UNLOCK: SYNCH_EV_READERUNLOCK);
}
int c = 0;
// the waiter under consideration to wake, or zero
PerThreadSynch *w = nullptr;
// the predecessor to w or zero
PerThreadSynch *pw = nullptr;
// head of the list searched previously, or zero
PerThreadSynch *old_h = nullptr;
// a condition that's known to be false.
const Condition *known_false = nullptr;
PerThreadSynch *wake_list = kPerThreadSynchNull; // list of threads to wake
intptr_t wr_wait = 0; // set to kMuWrWait if we wake a reader and a
// later writer could have acquired the lock
// (starvation avoidance)
ABSL_RAW_CHECK(waitp == nullptr || waitp->thread->waitp == nullptr ||
waitp->thread->suppress_fatal_errors,
"detected illegal recursion into Mutex code");
// This loop finds threads wake_list to wakeup if any, and removes them from
// the list of waiters. In addition, it places waitp.thread on the queue of
// waiters if waitp is non-zero.
for (;;) {
v = mu_.load(std::memory_order_relaxed);
if ((v & kMuWriter) != 0 && (v & (kMuWait | kMuDesig)) != kMuWait &&
waitp == nullptr) {
// fast writer release (writer with no waiters or with designated waker)
if (mu_.compare_exchange_strong(v, v & ~(kMuWrWait | kMuWriter),
std::memory_order_release,
std::memory_order_relaxed)) {
return;
}
} else if ((v & (kMuReader | kMuWait)) == kMuReader && waitp == nullptr) {
// fast reader release (reader with no waiters)
intptr_t clear = ExactlyOneReader(v) ? kMuReader | kMuOne : kMuOne;
if (mu_.compare_exchange_strong(v, v - clear,
std::memory_order_release,
std::memory_order_relaxed)) {
return;
}
} else if ((v & kMuSpin) == 0 && // attempt to get spinlock
mu_.compare_exchange_strong(v, v | kMuSpin,
std::memory_order_acquire,
std::memory_order_relaxed)) {
if ((v & kMuWait) == 0) { // no one to wake
intptr_t nv;
bool do_enqueue = true; // always Enqueue() the first time
ABSL_RAW_CHECK(waitp != nullptr,
"UnlockSlow is confused"); // about to sleep
do { // must loop to release spinlock as reader count may change
v = mu_.load(std::memory_order_relaxed);
// decrement reader count if there are readers
intptr_t new_readers = (v >= kMuOne)? v - kMuOne : v;
PerThreadSynch *new_h = nullptr;
if (do_enqueue) {
// If we are enqueuing on a CondVar (waitp->cv_word != nullptr) then
// we must not retry here. The initial attempt will always have
// succeeded, further attempts would enqueue us against *this due to
// Fer() handling.
do_enqueue = (waitp->cv_word == nullptr);
new_h = Enqueue(nullptr, waitp, new_readers, kMuIsCond);
}
intptr_t clear = kMuWrWait | kMuWriter; // by default clear write bit
if ((v & kMuWriter) == 0 && ExactlyOneReader(v)) { // last reader
clear = kMuWrWait | kMuReader; // clear read bit
}
nv = (v & kMuLow & ~clear & ~kMuSpin);
if (new_h != nullptr) {
nv |= kMuWait | reinterpret_cast<intptr_t>(new_h);
} else { // new_h could be nullptr if we queued ourselves on a
// CondVar
// In that case, we must place the reader count back in the mutex
// word, as Enqueue() did not store it in the new waiter.
nv |= new_readers & kMuHigh;
}
// release spinlock & our lock; retry if reader-count changed
// (writer count cannot change since we hold lock)
} while (!mu_.compare_exchange_weak(v, nv,
std::memory_order_release,
std::memory_order_relaxed));
break;
}
// There are waiters.
// Set h to the head of the circular waiter list.
PerThreadSynch *h = GetPerThreadSynch(v);
if ((v & kMuReader) != 0 && (h->readers & kMuHigh) > kMuOne) {
// a reader but not the last
h->readers -= kMuOne; // release our lock
intptr_t nv = v; // normally just release spinlock
if (waitp != nullptr) { // but waitp!=nullptr => must queue ourselves
PerThreadSynch *new_h = Enqueue(h, waitp, v, kMuIsCond);
ABSL_RAW_CHECK(new_h != nullptr,
"waiters disappeared during Enqueue()!");
nv &= kMuLow;
nv |= kMuWait | reinterpret_cast<intptr_t>(new_h);
}
mu_.store(nv, std::memory_order_release); // release spinlock
// can release with a store because there were waiters
break;
}
// Either we didn't search before, or we marked the queue
// as "maybe_unlocking" and no one else should have changed it.
ABSL_RAW_CHECK(old_h == nullptr || h->maybe_unlocking,
"Mutex queue changed beneath us");
// The lock is becoming free, and there's a waiter
if (old_h != nullptr &&
!old_h->may_skip) { // we used old_h as a terminator
old_h->may_skip = true; // allow old_h to skip once more
ABSL_RAW_CHECK(old_h->skip == nullptr, "illegal skip from head");
if (h != old_h && MuSameCondition(old_h, old_h->next)) {
old_h->skip = old_h->next; // old_h not head & can skip to successor
}
}
if (h->next->waitp->how == kExclusive &&
Condition::GuaranteedEqual(h->next->waitp->cond, nullptr)) {
// easy case: writer with no condition; no need to search
pw = h; // wake w, the successor of h (=pw)
w = h->next;
w->wake = true;
// We are waking up a writer. This writer may be racing against
// an already awake reader for the lock. We want the
// writer to usually win this race,
// because if it doesn't, we can potentially keep taking a reader
// perpetually and writers will starve. Worse than
// that, this can also starve other readers if kMuWrWait gets set
// later.
wr_wait = kMuWrWait;
} else if (w != nullptr && (w->waitp->how == kExclusive || h == old_h)) {
// we found a waiter w to wake on a previous iteration and either it's
// a writer, or we've searched the entire list so we have all the
// readers.
if (pw == nullptr) { // if w's predecessor is unknown, it must be h
pw = h;
}
} else {
// At this point we don't know all the waiters to wake, and the first
// waiter has a condition or is a reader. We avoid searching over
// waiters we've searched on previous iterations by starting at
// old_h if it's set. If old_h==h, there's no one to wakeup at all.
if (old_h == h) { // we've searched before, and nothing's new
// so there's no one to wake.
intptr_t nv = (v & ~(kMuReader|kMuWriter|kMuWrWait));
h->readers = 0;
h->maybe_unlocking = false; // finished unlocking
if (waitp != nullptr) { // we must queue ourselves and sleep
PerThreadSynch *new_h = Enqueue(h, waitp, v, kMuIsCond);
nv &= kMuLow;
if (new_h != nullptr) {
nv |= kMuWait | reinterpret_cast<intptr_t>(new_h);
} // else new_h could be nullptr if we queued ourselves on a
// CondVar
}
// release spinlock & lock
// can release with a store because there were waiters
mu_.store(nv, std::memory_order_release);
break;
}
// set up to walk the list
PerThreadSynch *w_walk; // current waiter during list walk
PerThreadSynch *pw_walk; // previous waiter during list walk
if (old_h != nullptr) { // we've searched up to old_h before
pw_walk = old_h;
w_walk = old_h->next;
} else { // no prior search, start at beginning
pw_walk =
nullptr; // h->next's predecessor may change; don't record it
w_walk = h->next;
}
h->may_skip = false; // ensure we never skip past h in future searches
// even if other waiters are queued after it.
ABSL_RAW_CHECK(h->skip == nullptr, "illegal skip from head");
h->maybe_unlocking = true; // we're about to scan the waiter list
// without the spinlock held.
// Enqueue must be conservative about
// priority queuing.
// We must release the spinlock to evaluate the conditions.
mu_.store(v, std::memory_order_release); // release just spinlock
// can release with a store because there were waiters
// h is the last waiter queued, and w_walk the first unsearched waiter.
// Without the spinlock, the locations mu_ and h->next may now change
// underneath us, but since we hold the lock itself, the only legal
// change is to add waiters between h and w_walk. Therefore, it's safe
// to walk the path from w_walk to h inclusive. (TryRemove() can remove
// a waiter anywhere, but it acquires both the spinlock and the Mutex)
old_h = h; // remember we searched to here
// Walk the path upto and including h looking for waiters we can wake.
while (pw_walk != h) {
w_walk->wake = false;
if (w_walk->waitp->cond ==
nullptr || // no condition => vacuously true OR
(w_walk->waitp->cond != known_false &&
// this thread's condition is not known false, AND
// is in fact true
EvalConditionIgnored(this, w_walk->waitp->cond))) {
if (w == nullptr) {
w_walk->wake = true; // can wake this waiter
w = w_walk;
pw = pw_walk;
if (w_walk->waitp->how == kExclusive) {
wr_wait = kMuWrWait;
break; // bail if waking this writer
}
} else if (w_walk->waitp->how == kShared) { // wake if a reader
w_walk->wake = true;
} else { // writer with true condition
wr_wait = kMuWrWait;
}
} else { // can't wake; condition false
known_false = w_walk->waitp->cond; // remember last false condition
}
if (w_walk->wake) { // we're waking reader w_walk
pw_walk = w_walk; // don't skip similar waiters
} else { // not waking; skip as much as possible
pw_walk = Skip(w_walk);
}
// If pw_walk == h, then load of pw_walk->next can race with
// concurrent write in Enqueue(). However, at the same time
// we do not need to do the load, because we will bail out
// from the loop anyway.
if (pw_walk != h) {
w_walk = pw_walk->next;
}
}
continue; // restart for(;;)-loop to wakeup w or to find more waiters
}
ABSL_RAW_CHECK(pw->next == w, "pw not w's predecessor");
// The first (and perhaps only) waiter we've chosen to wake is w, whose
// predecessor is pw. If w is a reader, we must wake all the other
// waiters with wake==true as well. We may also need to queue
// ourselves if waitp != null. The spinlock and the lock are still
// held.
// This traverses the list in [ pw->next, h ], where h is the head,
// removing all elements with wake==true and placing them in the
// singly-linked list wake_list. Returns the new head.
h = DequeueAllWakeable(h, pw, &wake_list);
intptr_t nv = (v & kMuEvent) | kMuDesig;
// assume no waiters left,
// set kMuDesig for INV1a
if (waitp != nullptr) { // we must queue ourselves and sleep
h = Enqueue(h, waitp, v, kMuIsCond);
// h is new last waiter; could be null if we queued ourselves on a
// CondVar
}
ABSL_RAW_CHECK(wake_list != kPerThreadSynchNull,
"unexpected empty wake list");
if (h != nullptr) { // there are waiters left
h->readers = 0;
h->maybe_unlocking = false; // finished unlocking
nv |= wr_wait | kMuWait | reinterpret_cast<intptr_t>(h);
}
// release both spinlock & lock
// can release with a store because there were waiters
mu_.store(nv, std::memory_order_release);
break; // out of for(;;)-loop
}
c = Delay(c, AGGRESSIVE); // aggressive here; no one can proceed till we do
} // end of for(;;)-loop
if (wake_list != kPerThreadSynchNull) {
int64_t enqueue_timestamp = wake_list->waitp->contention_start_cycles;
bool cond_waiter = wake_list->cond_waiter;
do {
wake_list = Wakeup(wake_list); // wake waiters
} while (wake_list != kPerThreadSynchNull);
if (!cond_waiter) {
// Sample lock contention events only if the (first) waiter was trying to
// acquire the lock, not waiting on a condition variable or Condition.
int64_t wait_cycles = base_internal::CycleClock::Now() - enqueue_timestamp;
mutex_tracer("slow release", this, wait_cycles);
ABSL_TSAN_MUTEX_PRE_DIVERT(this, 0);
submit_profile_data(enqueue_timestamp);
ABSL_TSAN_MUTEX_POST_DIVERT(this, 0);
}
}
}
// Used by CondVar implementation to reacquire mutex after waking from
// condition variable. This routine is used instead of Lock() because the
// waiting thread may have been moved from the condition variable queue to the
// mutex queue without a wakeup, by Trans(). In that case, when the thread is
// finally woken, the woken thread will believe it has been woken from the
// condition variable (i.e. its PC will be in when in the CondVar code), when
// in fact it has just been woken from the mutex. Thus, it must enter the slow
// path of the mutex in the same state as if it had just woken from the mutex.
// That is, it must ensure to clear kMuDesig (INV1b).
void Mutex::Trans(MuHow how) {
this->LockSlow(how, nullptr, kMuHasBlocked | kMuIsCond);
}
// Used by CondVar implementation to effectively wake thread w from the
// condition variable. If this mutex is free, we simply wake the thread.
// It will later acquire the mutex with high probability. Otherwise, we
// enqueue thread w on this mutex.
void Mutex::Fer(PerThreadSynch *w) {
int c = 0;
ABSL_RAW_CHECK(w->waitp->cond == nullptr,
"Mutex::Fer while waiting on Condition");
ABSL_RAW_CHECK(!w->waitp->timeout.has_timeout(),
"Mutex::Fer while in timed wait");
ABSL_RAW_CHECK(w->waitp->cv_word == nullptr,
"Mutex::Fer with pending CondVar queueing");
for (;;) {
intptr_t v = mu_.load(std::memory_order_relaxed);
// Note: must not queue if the mutex is unlocked (nobody will wake it).
// For example, we can have only kMuWait (conditional) or maybe
// kMuWait|kMuWrWait.
// conflicting != 0 implies that the waking thread cannot currently take
// the mutex, which in turn implies that someone else has it and can wake
// us if we queue.
const intptr_t conflicting =
kMuWriter | (w->waitp->how == kShared ? 0 : kMuReader);
if ((v & conflicting) == 0) {
w->next = nullptr;
w->state.store(PerThreadSynch::kAvailable, std::memory_order_release);
IncrementSynchSem(this, w);
return;
} else {
if ((v & (kMuSpin|kMuWait)) == 0) { // no waiters
// This thread tries to become the one and only waiter.
PerThreadSynch *new_h = Enqueue(nullptr, w->waitp, v, kMuIsCond);
ABSL_RAW_CHECK(new_h != nullptr,
"Enqueue failed"); // we must queue ourselves
if (mu_.compare_exchange_strong(
v, reinterpret_cast<intptr_t>(new_h) | (v & kMuLow) | kMuWait,
std::memory_order_release, std::memory_order_relaxed)) {
return;
}
} else if ((v & kMuSpin) == 0 &&
mu_.compare_exchange_strong(v, v | kMuSpin | kMuWait)) {
PerThreadSynch *h = GetPerThreadSynch(v);
PerThreadSynch *new_h = Enqueue(h, w->waitp, v, kMuIsCond);
ABSL_RAW_CHECK(new_h != nullptr,
"Enqueue failed"); // we must queue ourselves
do {
v = mu_.load(std::memory_order_relaxed);
} while (!mu_.compare_exchange_weak(
v,
(v & kMuLow & ~kMuSpin) | kMuWait |
reinterpret_cast<intptr_t>(new_h),
std::memory_order_release, std::memory_order_relaxed));
return;
}
}
c = Delay(c, GENTLE);
}
}
void Mutex::AssertHeld() const {
if ((mu_.load(std::memory_order_relaxed) & kMuWriter) == 0) {
SynchEvent *e = GetSynchEvent(this);
ABSL_RAW_LOG(FATAL, "thread should hold write lock on Mutex %p %s",
static_cast<const void *>(this),
(e == nullptr ? "" : e->name));
}
}
void Mutex::AssertReaderHeld() const {
if ((mu_.load(std::memory_order_relaxed) & (kMuReader | kMuWriter)) == 0) {
SynchEvent *e = GetSynchEvent(this);
ABSL_RAW_LOG(
FATAL, "thread should hold at least a read lock on Mutex %p %s",
static_cast<const void *>(this), (e == nullptr ? "" : e->name));
}
}
// -------------------------------- condition variables
static const intptr_t kCvSpin = 0x0001L; // spinlock protects waiter list
static const intptr_t kCvEvent = 0x0002L; // record events
static const intptr_t kCvLow = 0x0003L; // low order bits of CV
// Hack to make constant values available to gdb pretty printer
enum { kGdbCvSpin = kCvSpin, kGdbCvEvent = kCvEvent, kGdbCvLow = kCvLow, };
static_assert(PerThreadSynch::kAlignment > kCvLow,
"PerThreadSynch::kAlignment must be greater than kCvLow");
void CondVar::EnableDebugLog(const char *name) {
SynchEvent *e = EnsureSynchEvent(&this->cv_, name, kCvEvent, kCvSpin);
e->log = true;
UnrefSynchEvent(e);
}
CondVar::~CondVar() {
if ((cv_.load(std::memory_order_relaxed) & kCvEvent) != 0) {
ForgetSynchEvent(&this->cv_, kCvEvent, kCvSpin);
}
}
// Remove thread s from the list of waiters on this condition variable.
void CondVar::Remove(PerThreadSynch *s) {
intptr_t v;
int c = 0;
for (v = cv_.load(std::memory_order_relaxed);;
v = cv_.load(std::memory_order_relaxed)) {
if ((v & kCvSpin) == 0 && // attempt to acquire spinlock
cv_.compare_exchange_strong(v, v | kCvSpin,
std::memory_order_acquire,
std::memory_order_relaxed)) {
PerThreadSynch *h = reinterpret_cast<PerThreadSynch *>(v & ~kCvLow);
if (h != nullptr) {
PerThreadSynch *w = h;
while (w->next != s && w->next != h) { // search for thread
w = w->next;
}
if (w->next == s) { // found thread; remove it
w->next = s->next;
if (h == s) {
h = (w == s) ? nullptr : w;
}
s->next = nullptr;
s->state.store(PerThreadSynch::kAvailable, std::memory_order_release);
}
}
// release spinlock
cv_.store((v & kCvEvent) | reinterpret_cast<intptr_t>(h),
std::memory_order_release);
return;
} else {
c = Delay(c, GENTLE); // try again after a delay
}
}
}
// Queue thread waitp->thread on condition variable word cv_word using
// wait parameters waitp.
// We split this into a separate routine, rather than simply doing it as part
// of WaitCommon(). If we were to queue ourselves on the condition variable
// before calling Mutex::UnlockSlow(), the Mutex code might be re-entered (via
// the logging code, or via a Condition function) and might potentially attempt
// to block this thread. That would be a problem if the thread were already on
// a the condition variable waiter queue. Thus, we use the waitp->cv_word
// to tell the unlock code to call CondVarEnqueue() to queue the thread on the
// condition variable queue just before the mutex is to be unlocked, and (most
// importantly) after any call to an external routine that might re-enter the
// mutex code.
static void CondVarEnqueue(SynchWaitParams *waitp) {
// This thread might be transferred to the Mutex queue by Fer() when
// we are woken. To make sure that is what happens, Enqueue() doesn't
// call CondVarEnqueue() again but instead uses its normal code. We
// must do this before we queue ourselves so that cv_word will be null
// when seen by the dequeuer, who may wish immediately to requeue
// this thread on another queue.
std::atomic<intptr_t> *cv_word = waitp->cv_word;
waitp->cv_word = nullptr;
intptr_t v = cv_word->load(std::memory_order_relaxed);
int c = 0;
while ((v & kCvSpin) != 0 || // acquire spinlock
!cv_word->compare_exchange_weak(v, v | kCvSpin,
std::memory_order_acquire,
std::memory_order_relaxed)) {
c = Delay(c, GENTLE);
v = cv_word->load(std::memory_order_relaxed);
}
ABSL_RAW_CHECK(waitp->thread->waitp == nullptr, "waiting when shouldn't be");
waitp->thread->waitp = waitp; // prepare ourselves for waiting
PerThreadSynch *h = reinterpret_cast<PerThreadSynch *>(v & ~kCvLow);
if (h == nullptr) { // add this thread to waiter list
waitp->thread->next = waitp->thread;
} else {
waitp->thread->next = h->next;
h->next = waitp->thread;
}
waitp->thread->state.store(PerThreadSynch::kQueued,
std::memory_order_relaxed);
cv_word->store((v & kCvEvent) | reinterpret_cast<intptr_t>(waitp->thread),
std::memory_order_release);
}
bool CondVar::WaitCommon(Mutex *mutex, KernelTimeout t) {
bool rc = false; // return value; true iff we timed-out
intptr_t mutex_v = mutex->mu_.load(std::memory_order_relaxed);
Mutex::MuHow mutex_how = ((mutex_v & kMuWriter) != 0) ? kExclusive : kShared;
ABSL_TSAN_MUTEX_PRE_UNLOCK(mutex, TsanFlags(mutex_how));
// maybe trace this call
intptr_t v = cv_.load(std::memory_order_relaxed);
cond_var_tracer("Wait", this);
if ((v & kCvEvent) != 0) {
PostSynchEvent(this, SYNCH_EV_WAIT);
}
// Release mu and wait on condition variable.
SynchWaitParams waitp(mutex_how, nullptr, t, mutex,
Synch_GetPerThreadAnnotated(mutex), &cv_);
// UnlockSlow() will call CondVarEnqueue() just before releasing the
// Mutex, thus queuing this thread on the condition variable. See
// CondVarEnqueue() for the reasons.
mutex->UnlockSlow(&waitp);
// wait for signal
while (waitp.thread->state.load(std::memory_order_acquire) ==
PerThreadSynch::kQueued) {
if (!Mutex::DecrementSynchSem(mutex, waitp.thread, t)) {
this->Remove(waitp.thread);
rc = true;
}
}
ABSL_RAW_CHECK(waitp.thread->waitp != nullptr, "not waiting when should be");
waitp.thread->waitp = nullptr; // cleanup
// maybe trace this call
cond_var_tracer("Unwait", this);
if ((v & kCvEvent) != 0) {
PostSynchEvent(this, SYNCH_EV_WAIT_RETURNING);
}
// From synchronization point of view Wait is unlock of the mutex followed
// by lock of the mutex. We've annotated start of unlock in the beginning
// of the function. Now, finish unlock and annotate lock of the mutex.
// (Trans is effectively lock).
ABSL_TSAN_MUTEX_POST_UNLOCK(mutex, TsanFlags(mutex_how));
ABSL_TSAN_MUTEX_PRE_LOCK(mutex, TsanFlags(mutex_how));
mutex->Trans(mutex_how); // Reacquire mutex
ABSL_TSAN_MUTEX_POST_LOCK(mutex, TsanFlags(mutex_how), 0);
return rc;
}
bool CondVar::WaitWithTimeout(Mutex *mu, absl::Duration timeout) {
return WaitWithDeadline(mu, DeadlineFromTimeout(timeout));
}
bool CondVar::WaitWithDeadline(Mutex *mu, absl::Time deadline) {
return WaitCommon(mu, KernelTimeout(deadline));
}
void CondVar::Wait(Mutex *mu) {
WaitCommon(mu, KernelTimeout::Never());
}
// Wake thread w
// If it was a timed wait, w will be waiting on w->cv
// Otherwise, if it was not a Mutex mutex, w will be waiting on w->sem
// Otherwise, w is transferred to the Mutex mutex via Mutex::Fer().
void CondVar::Wakeup(PerThreadSynch *w) {
if (w->waitp->timeout.has_timeout() || w->waitp->cvmu == nullptr) {
// The waiting thread only needs to observe "w->state == kAvailable" to be
// released, we must cache "cvmu" before clearing "next".
Mutex *mu = w->waitp->cvmu;
w->next = nullptr;
w->state.store(PerThreadSynch::kAvailable, std::memory_order_release);
Mutex::IncrementSynchSem(mu, w);
} else {
w->waitp->cvmu->Fer(w);
}
}
void CondVar::Signal() {
ABSL_TSAN_MUTEX_PRE_SIGNAL(nullptr, 0);
7 years ago
intptr_t v;
int c = 0;
for (v = cv_.load(std::memory_order_relaxed); v != 0;
v = cv_.load(std::memory_order_relaxed)) {
if ((v & kCvSpin) == 0 && // attempt to acquire spinlock
cv_.compare_exchange_strong(v, v | kCvSpin,
std::memory_order_acquire,
std::memory_order_relaxed)) {
PerThreadSynch *h = reinterpret_cast<PerThreadSynch *>(v & ~kCvLow);
PerThreadSynch *w = nullptr;
if (h != nullptr) { // remove first waiter
w = h->next;
if (w == h) {
h = nullptr;
} else {
h->next = w->next;
}
}
// release spinlock
cv_.store((v & kCvEvent) | reinterpret_cast<intptr_t>(h),
std::memory_order_release);
if (w != nullptr) {
CondVar::Wakeup(w); // wake waiter, if there was one
cond_var_tracer("Signal wakeup", this);
}
if ((v & kCvEvent) != 0) {
PostSynchEvent(this, SYNCH_EV_SIGNAL);
}
ABSL_TSAN_MUTEX_POST_SIGNAL(nullptr, 0);
7 years ago
return;
} else {
c = Delay(c, GENTLE);
}
}
ABSL_TSAN_MUTEX_POST_SIGNAL(nullptr, 0);
7 years ago
}
void CondVar::SignalAll () {
ABSL_TSAN_MUTEX_PRE_SIGNAL(nullptr, 0);
7 years ago
intptr_t v;
int c = 0;
for (v = cv_.load(std::memory_order_relaxed); v != 0;
v = cv_.load(std::memory_order_relaxed)) {
// empty the list if spinlock free
// We do this by simply setting the list to empty using
// compare and swap. We then have the entire list in our hands,
// which cannot be changing since we grabbed it while no one
// held the lock.
if ((v & kCvSpin) == 0 &&
cv_.compare_exchange_strong(v, v & kCvEvent, std::memory_order_acquire,
std::memory_order_relaxed)) {
PerThreadSynch *h = reinterpret_cast<PerThreadSynch *>(v & ~kCvLow);
if (h != nullptr) {
PerThreadSynch *w;
PerThreadSynch *n = h->next;
do { // for every thread, wake it up
w = n;
n = n->next;
CondVar::Wakeup(w);
} while (w != h);
cond_var_tracer("SignalAll wakeup", this);
}
if ((v & kCvEvent) != 0) {
PostSynchEvent(this, SYNCH_EV_SIGNALALL);
}
ABSL_TSAN_MUTEX_POST_SIGNAL(nullptr, 0);
7 years ago
return;
} else {
c = Delay(c, GENTLE); // try again after a delay
}
}
ABSL_TSAN_MUTEX_POST_SIGNAL(nullptr, 0);
7 years ago
}
void ReleasableMutexLock::Release() {
ABSL_RAW_CHECK(this->mu_ != nullptr,
"ReleasableMutexLock::Release may only be called once");
this->mu_->Unlock();
this->mu_ = nullptr;
}
#ifdef THREAD_SANITIZER
extern "C" void __tsan_read1(void *addr);
#else
#define __tsan_read1(addr) // do nothing if TSan not enabled
#endif
// A function that just returns its argument, dereferenced
static bool Dereference(void *arg) {
// ThreadSanitizer does not instrument this file for memory accesses.
// This function dereferences a user variable that can participate
// in a data race, so we need to manually tell TSan about this memory access.
__tsan_read1(arg);
return *(static_cast<bool *>(arg));
}
Condition::Condition() {} // null constructor, used for kTrue only
const Condition Condition::kTrue;
Condition::Condition(bool (*func)(void *), void *arg)
: eval_(&CallVoidPtrFunction),
function_(func),
method_(nullptr),
arg_(arg) {}
bool Condition::CallVoidPtrFunction(const Condition *c) {
return (*c->function_)(c->arg_);
}
Condition::Condition(const bool *cond)
: eval_(CallVoidPtrFunction),
function_(Dereference),
method_(nullptr),
// const_cast is safe since Dereference does not modify arg
arg_(const_cast<bool *>(cond)) {}
bool Condition::Eval() const {
// eval_ == null for kTrue
return (this->eval_ == nullptr) || (*this->eval_)(this);
}
bool Condition::GuaranteedEqual(const Condition *a, const Condition *b) {
if (a == nullptr) {
return b == nullptr || b->eval_ == nullptr;
}
if (b == nullptr || b->eval_ == nullptr) {
return a->eval_ == nullptr;
}
return a->eval_ == b->eval_ && a->function_ == b->function_ &&
a->arg_ == b->arg_ && a->method_ == b->method_;
}
Export of internal Abseil changes -- c99f979ad34f155fbeeea69b88bdc7458d89a21c by Derek Mauro <dmauro@google.com>: Remove a floating point division by zero test. This isn't testing behavior related to the library, and MSVC warns about it in opt mode. PiperOrigin-RevId: 285220804 -- 68b015491f0dbf1ab547994673281abd1f34cd4b by Gennadiy Rozental <rogeeff@google.com>: This CL introduces following changes to the class FlagImpl: * We eliminate the CommandLineFlagLocks struct. Instead callback guard and callback function are combined into a single CallbackData struct, while primary data lock is stored separately. * CallbackData member of class FlagImpl is initially set to be nullptr and is only allocated and initialized when a flag's callback is being set. For most flags we do not pay for the extra space and extra absl::Mutex now. * Primary data guard is stored in data_guard_ data member. This is a properly aligned character buffer of necessary size. During initialization of the flag we construct absl::Mutex in this space using placement new call. * We now avoid extra value copy after successful attempt to parse value out of string. Instead we swap flag's current value with tentative value we just produced. PiperOrigin-RevId: 285132636 -- ed45d118fb818969eb13094cf7827c885dfc562c by Tom Manshreck <shreck@google.com>: Change null-term* (and nul-term*) to NUL-term* in comments PiperOrigin-RevId: 285036610 -- 729619017944db895ce8d6d29c1995aa2e5628a5 by Derek Mauro <dmauro@google.com>: Use the Posix implementation of thread identity on MinGW. Some versions of MinGW suffer from thread_local bugs. PiperOrigin-RevId: 285022920 -- 39a25493503c76885bc3254c28f66a251c5b5bb0 by Greg Falcon <gfalcon@google.com>: Implementation detail change. Add further ABSL_NAMESPACE_BEGIN and _END annotation macros to files in Abseil. PiperOrigin-RevId: 285012012 GitOrigin-RevId: c99f979ad34f155fbeeea69b88bdc7458d89a21c Change-Id: I4c85d3704e45d11a9ac50d562f39640a6adbedc1
5 years ago
ABSL_NAMESPACE_END
7 years ago
} // namespace absl