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5bd06440e700fefd6eadd577d7d69c51f15c63e0 by Abseil Team <absl-team@google.com>:

Add if-guard to futex.h so that it doesn't fail to parse for unsupported platforms

PiperOrigin-RevId: 336880375

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8b3d3bb4ad123fc9f648f0e397b2eddd88dc0c02 by Derek Mauro <dmauro@google.com>:

Fix race in AddressIsReadable file descriptors using stronger memory ordering

PiperOrigin-RevId: 336874423

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1d8bf23747009cca29129b80c2793bc91443dd55 by Derek Mauro <dmauro@google.com>:

Avoid -Wundef warnings on ABSL_HAVE_THREAD_LOCAL

PiperOrigin-RevId: 336792406

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562a480f029c600c1d3b1428da6a9b09e8952a74 by Derek Mauro <dmauro@google.com>:

Fix preprocessor condition for symbols __tsan_mutex_read_lock and
__tsan_mutex_try_lock

PiperOrigin-RevId: 336732571
GitOrigin-RevId: 5bd06440e700fefd6eadd577d7d69c51f15c63e0
Change-Id: Id9bb331baec74b9d80c7b228959a7739bc30e694
pull/827/head
Abseil Team 4 years ago committed by Derek Mauro
parent 4b2fbb4adb
commit f3f785ab59
8 changed files with 28 additions and 19 deletions
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  1. 2
      absl/base/internal/exponential_biased_test.cc
  2. 2
      absl/base/internal/sysinfo.cc
  3. 2
      absl/container/internal/raw_hash_set.cc
  4. 9
      absl/debugging/internal/address_is_readable.cc
  5. 15
      absl/synchronization/internal/futex.h
  6. 4
      absl/synchronization/internal/waiter.cc
  7. 8
      absl/synchronization/internal/waiter.h
  8. 5
      absl/synchronization/mutex.cc

2
absl/base/internal/exponential_biased_test.cc
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@ -185,7 +185,7 @@ TEST(ExponentialBiasedTest, InitializationModes) {
ABSL_CONST_INIT static ExponentialBiased eb_static; ABSL_CONST_INIT static ExponentialBiased eb_static;
EXPECT_THAT(eb_static.GetSkipCount(2), Ge(0)); EXPECT_THAT(eb_static.GetSkipCount(2), Ge(0));
#if ABSL_HAVE_THREAD_LOCAL #ifdef ABSL_HAVE_THREAD_LOCAL
thread_local ExponentialBiased eb_thread; thread_local ExponentialBiased eb_thread;
EXPECT_THAT(eb_thread.GetSkipCount(2), Ge(0)); EXPECT_THAT(eb_thread.GetSkipCount(2), Ge(0));
#endif #endif

2
absl/base/internal/sysinfo.cc
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@ -426,7 +426,7 @@ pid_t GetTID() {
// userspace construct) to avoid unnecessary system calls. Without this caching, // userspace construct) to avoid unnecessary system calls. Without this caching,
// it can take roughly 98ns, while it takes roughly 1ns with this caching. // it can take roughly 98ns, while it takes roughly 1ns with this caching.
pid_t GetCachedTID() { pid_t GetCachedTID() {
#if ABSL_HAVE_THREAD_LOCAL #ifdef ABSL_HAVE_THREAD_LOCAL
static thread_local pid_t thread_id = GetTID(); static thread_local pid_t thread_id = GetTID();
return thread_id; return thread_id;
#else #else

2
absl/container/internal/raw_hash_set.cc
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@ -27,7 +27,7 @@ constexpr size_t Group::kWidth;
// Returns "random" seed. // Returns "random" seed.
inline size_t RandomSeed() { inline size_t RandomSeed() {
#if ABSL_HAVE_THREAD_LOCAL #ifdef ABSL_HAVE_THREAD_LOCAL
static thread_local size_t counter = 0; static thread_local size_t counter = 0;
size_t value = ++counter; size_t value = ++counter;
#else // ABSL_HAVE_THREAD_LOCAL #else // ABSL_HAVE_THREAD_LOCAL

9
absl/debugging/internal/address_is_readable.cc
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@ -68,6 +68,7 @@ static void Unpack(uint64_t x, int *pid, int *read_fd, int *write_fd) {
// unimplemented. // unimplemented.
// This is a namespace-scoped variable for correct zero-initialization. // This is a namespace-scoped variable for correct zero-initialization.
static std::atomic<uint64_t> pid_and_fds; // initially 0, an invalid pid. static std::atomic<uint64_t> pid_and_fds; // initially 0, an invalid pid.
bool AddressIsReadable(const void *addr) { bool AddressIsReadable(const void *addr) {
absl::base_internal::ErrnoSaver errno_saver; absl::base_internal::ErrnoSaver errno_saver;
// We test whether a byte is readable by using write(). Normally, this would // We test whether a byte is readable by using write(). Normally, this would
@ -86,7 +87,7 @@ bool AddressIsReadable(const void *addr) {
int pid; int pid;
int read_fd; int read_fd;
int write_fd; int write_fd;
uint64_t local_pid_and_fds = pid_and_fds.load(std::memory_order_relaxed); uint64_t local_pid_and_fds = pid_and_fds.load(std::memory_order_acquire);
Unpack(local_pid_and_fds, &pid, &read_fd, &write_fd); Unpack(local_pid_and_fds, &pid, &read_fd, &write_fd);
while (current_pid != pid) { while (current_pid != pid) {
int p[2]; int p[2];
@ -98,13 +99,13 @@ bool AddressIsReadable(const void *addr) {
fcntl(p[1], F_SETFD, FD_CLOEXEC); fcntl(p[1], F_SETFD, FD_CLOEXEC);
uint64_t new_pid_and_fds = Pack(current_pid, p[0], p[1]); uint64_t new_pid_and_fds = Pack(current_pid, p[0], p[1]);
if (pid_and_fds.compare_exchange_strong( if (pid_and_fds.compare_exchange_strong(
local_pid_and_fds, new_pid_and_fds, std::memory_order_relaxed, local_pid_and_fds, new_pid_and_fds, std::memory_order_release,
std::memory_order_relaxed)) { std::memory_order_relaxed)) {
local_pid_and_fds = new_pid_and_fds; // fds exposed to other threads local_pid_and_fds = new_pid_and_fds; // fds exposed to other threads
} else { // fds not exposed to other threads; we can close them. } else { // fds not exposed to other threads; we can close them.
close(p[0]); close(p[0]);
close(p[1]); close(p[1]);
local_pid_and_fds = pid_and_fds.load(std::memory_order_relaxed); local_pid_and_fds = pid_and_fds.load(std::memory_order_acquire);
} }
Unpack(local_pid_and_fds, &pid, &read_fd, &write_fd); Unpack(local_pid_and_fds, &pid, &read_fd, &write_fd);
} }
@ -124,7 +125,7 @@ bool AddressIsReadable(const void *addr) {
// If pid_and_fds contains the problematic file descriptors we just used, // If pid_and_fds contains the problematic file descriptors we just used,
// this call will forget them, and the loop will try again. // this call will forget them, and the loop will try again.
pid_and_fds.compare_exchange_strong(local_pid_and_fds, 0, pid_and_fds.compare_exchange_strong(local_pid_and_fds, 0,
std::memory_order_relaxed, std::memory_order_release,
std::memory_order_relaxed); std::memory_order_relaxed);
} }
} while (errno == EBADF); } while (errno == EBADF);

15
absl/synchronization/internal/futex.h
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@ -38,6 +38,19 @@
#include "absl/base/optimization.h" #include "absl/base/optimization.h"
#include "absl/synchronization/internal/kernel_timeout.h" #include "absl/synchronization/internal/kernel_timeout.h"
#ifdef ABSL_INTERNAL_HAVE_FUTEX
#error ABSL_INTERNAL_HAVE_FUTEX may not be set on the command line
#elif defined(__BIONIC__)
// Bionic supports all the futex operations we need even when some of the futex
// definitions are missing.
#define ABSL_INTERNAL_HAVE_FUTEX
#elif defined(__linux__) && defined(FUTEX_CLOCK_REALTIME)
// FUTEX_CLOCK_REALTIME requires Linux >= 2.6.28.
#define ABSL_INTERNAL_HAVE_FUTEX
#endif
#ifdef ABSL_INTERNAL_HAVE_FUTEX
namespace absl { namespace absl {
ABSL_NAMESPACE_BEGIN ABSL_NAMESPACE_BEGIN
namespace synchronization_internal { namespace synchronization_internal {
@ -136,4 +149,6 @@ class Futex : public FutexImpl {};
ABSL_NAMESPACE_END ABSL_NAMESPACE_END
} // namespace absl } // namespace absl
#endif // ABSL_INTERNAL_HAVE_FUTEX
#endif // ABSL_SYNCHRONIZATION_INTERNAL_FUTEX_H_ #endif // ABSL_SYNCHRONIZATION_INTERNAL_FUTEX_H_

4
absl/synchronization/internal/waiter.cc
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@ -48,10 +48,6 @@
#include "absl/base/optimization.h" #include "absl/base/optimization.h"
#include "absl/synchronization/internal/kernel_timeout.h" #include "absl/synchronization/internal/kernel_timeout.h"
#if ABSL_WAITER_MODE == ABSL_WAITER_MODE_FUTEX
#include "absl/synchronization/internal/futex.h"
#endif
namespace absl { namespace absl {
ABSL_NAMESPACE_BEGIN ABSL_NAMESPACE_BEGIN

8
absl/synchronization/internal/waiter.h
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@ -36,6 +36,7 @@
#include <cstdint> #include <cstdint>
#include "absl/base/internal/thread_identity.h" #include "absl/base/internal/thread_identity.h"
#include "absl/synchronization/internal/futex.h"
#include "absl/synchronization/internal/kernel_timeout.h" #include "absl/synchronization/internal/kernel_timeout.h"
// May be chosen at compile time via -DABSL_FORCE_WAITER_MODE=<index> // May be chosen at compile time via -DABSL_FORCE_WAITER_MODE=<index>
@ -48,12 +49,7 @@
#define ABSL_WAITER_MODE ABSL_FORCE_WAITER_MODE #define ABSL_WAITER_MODE ABSL_FORCE_WAITER_MODE
#elif defined(_WIN32) && _WIN32_WINNT >= _WIN32_WINNT_VISTA #elif defined(_WIN32) && _WIN32_WINNT >= _WIN32_WINNT_VISTA
#define ABSL_WAITER_MODE ABSL_WAITER_MODE_WIN32 #define ABSL_WAITER_MODE ABSL_WAITER_MODE_WIN32
#elif defined(__BIONIC__) #elif defined(ABSL_INTERNAL_HAVE_FUTEX)
// Bionic supports all the futex operations we need even when some of the futex
// definitions are missing.
#define ABSL_WAITER_MODE ABSL_WAITER_MODE_FUTEX
#elif defined(__linux__) && defined(FUTEX_CLOCK_REALTIME)
// FUTEX_CLOCK_REALTIME requires Linux >= 2.6.28.
#define ABSL_WAITER_MODE ABSL_WAITER_MODE_FUTEX #define ABSL_WAITER_MODE ABSL_WAITER_MODE_FUTEX
#elif defined(ABSL_HAVE_SEMAPHORE_H) #elif defined(ABSL_HAVE_SEMAPHORE_H)
#define ABSL_WAITER_MODE ABSL_WAITER_MODE_SEM #define ABSL_WAITER_MODE ABSL_WAITER_MODE_SEM

5
absl/synchronization/mutex.cc
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@ -50,6 +50,7 @@
#include "absl/base/internal/spinlock.h" #include "absl/base/internal/spinlock.h"
#include "absl/base/internal/sysinfo.h" #include "absl/base/internal/sysinfo.h"
#include "absl/base/internal/thread_identity.h" #include "absl/base/internal/thread_identity.h"
#include "absl/base/internal/tsan_mutex_interface.h"
#include "absl/base/port.h" #include "absl/base/port.h"
#include "absl/debugging/stacktrace.h" #include "absl/debugging/stacktrace.h"
#include "absl/debugging/symbolize.h" #include "absl/debugging/symbolize.h"
@ -705,7 +706,7 @@ static constexpr bool kDebugMode = false;
static constexpr bool kDebugMode = true; static constexpr bool kDebugMode = true;
#endif #endif
#ifdef ABSL_HAVE_THREAD_SANITIZER #ifdef ABSL_INTERNAL_HAVE_TSAN_INTERFACE
static unsigned TsanFlags(Mutex::MuHow how) { static unsigned TsanFlags(Mutex::MuHow how) {
return how == kShared ? __tsan_mutex_read_lock : 0; return how == kShared ? __tsan_mutex_read_lock : 0;
} }
@ -1767,7 +1768,7 @@ static inline bool EvalConditionAnnotated(const Condition *cond, Mutex *mu,
// All memory accesses are ignored inside of mutex operations + for unlock // All memory accesses are ignored inside of mutex operations + for unlock
// operation tsan considers that we've already released the mutex. // operation tsan considers that we've already released the mutex.
bool res = false; bool res = false;
#ifdef ABSL_HAVE_THREAD_SANITIZER #ifdef ABSL_INTERNAL_HAVE_TSAN_INTERFACE
const int flags = read_lock ? __tsan_mutex_read_lock : 0; const int flags = read_lock ? __tsan_mutex_read_lock : 0;
const int tryflags = flags | (trylock ? __tsan_mutex_try_lock : 0); const int tryflags = flags | (trylock ? __tsan_mutex_try_lock : 0);
#endif #endif

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