Abseil Common Libraries (C++) (grcp 依赖) https://abseil.io/
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Export of internal Abseil changes -- f012012ef78234a6a4585321b67d7b7c92ebc266 by Laramie Leavitt <lar@google.com>: Slight restructuring of absl/random/internal randen implementation. Convert round-keys.inc into randen_round_keys.cc file. Consistently use a 128-bit pointer type for internal method parameters. This allows simpler pointer arithmetic in C++ & permits removal of some constants and casts. Remove some redundancy in comments & constexpr variables. Specifically, all references to Randen algorithm parameters use RandenTraits; duplication in RandenSlow removed. PiperOrigin-RevId: 312190313 -- dc8b42e054046741e9ed65335bfdface997c6063 by Abseil Team <absl-team@google.com>: Internal change. PiperOrigin-RevId: 312167304 -- f13d248fafaf206492c1362c3574031aea3abaf7 by Matthew Brown <matthewbr@google.com>: Cleanup StrFormat extensions a little. PiperOrigin-RevId: 312166336 -- 9d9117589667afe2332bb7ad42bc967ca7c54502 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 312105213 -- 9a12b9b3aa0e59b8ee6cf9408ed0029045543a9b by Abseil Team <absl-team@google.com>: Complete IGNORE_TYPE macro renaming. PiperOrigin-RevId: 311999699 -- 64756f20d61021d999bd0d4c15e9ad3857382f57 by Gennadiy Rozental <rogeeff@google.com>: Switch to fixed bytes specific default value. This fixes the Abseil Flags for big endian platforms. PiperOrigin-RevId: 311844448 -- bdbe6b5b29791dbc3816ada1828458b3010ff1e9 by Laramie Leavitt <lar@google.com>: Change many distribution tests to use pcg_engine as a deterministic source of entropy. It's reasonable to test that the BitGen itself has good entropy, however when testing the cross product of all random distributions x all the architecture variations x all submitted changes results in a large number of tests. In order to account for these failures while still using good entropy requires that our allowed sigma need to account for all of these independent tests. Our current sigma values are too restrictive, and we see a lot of failures, so we have to either relax the sigma values or convert some of the statistical tests to use deterministic values. This changelist does the latter. PiperOrigin-RevId: 311840096 GitOrigin-RevId: f012012ef78234a6a4585321b67d7b7c92ebc266 Change-Id: Ic84886f38ff30d7d72c126e9b63c9a61eb729a1a
5 years ago
//
// 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.
//
// Most users requiring mutual exclusion should use Mutex.
// SpinLock is provided for use in two situations:
Export of internal Abseil changes -- f012012ef78234a6a4585321b67d7b7c92ebc266 by Laramie Leavitt <lar@google.com>: Slight restructuring of absl/random/internal randen implementation. Convert round-keys.inc into randen_round_keys.cc file. Consistently use a 128-bit pointer type for internal method parameters. This allows simpler pointer arithmetic in C++ & permits removal of some constants and casts. Remove some redundancy in comments & constexpr variables. Specifically, all references to Randen algorithm parameters use RandenTraits; duplication in RandenSlow removed. PiperOrigin-RevId: 312190313 -- dc8b42e054046741e9ed65335bfdface997c6063 by Abseil Team <absl-team@google.com>: Internal change. PiperOrigin-RevId: 312167304 -- f13d248fafaf206492c1362c3574031aea3abaf7 by Matthew Brown <matthewbr@google.com>: Cleanup StrFormat extensions a little. PiperOrigin-RevId: 312166336 -- 9d9117589667afe2332bb7ad42bc967ca7c54502 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 312105213 -- 9a12b9b3aa0e59b8ee6cf9408ed0029045543a9b by Abseil Team <absl-team@google.com>: Complete IGNORE_TYPE macro renaming. PiperOrigin-RevId: 311999699 -- 64756f20d61021d999bd0d4c15e9ad3857382f57 by Gennadiy Rozental <rogeeff@google.com>: Switch to fixed bytes specific default value. This fixes the Abseil Flags for big endian platforms. PiperOrigin-RevId: 311844448 -- bdbe6b5b29791dbc3816ada1828458b3010ff1e9 by Laramie Leavitt <lar@google.com>: Change many distribution tests to use pcg_engine as a deterministic source of entropy. It's reasonable to test that the BitGen itself has good entropy, however when testing the cross product of all random distributions x all the architecture variations x all submitted changes results in a large number of tests. In order to account for these failures while still using good entropy requires that our allowed sigma need to account for all of these independent tests. Our current sigma values are too restrictive, and we see a lot of failures, so we have to either relax the sigma values or convert some of the statistical tests to use deterministic values. This changelist does the latter. PiperOrigin-RevId: 311840096 GitOrigin-RevId: f012012ef78234a6a4585321b67d7b7c92ebc266 Change-Id: Ic84886f38ff30d7d72c126e9b63c9a61eb729a1a
5 years ago
// - for use in code that Mutex itself depends on
// - for async signal safety (see below)
// SpinLock is async signal safe. If a spinlock is used within a signal
// handler, all code that acquires the lock must ensure that the signal cannot
// arrive while they are holding the lock. Typically, this is done by blocking
// the signal.
#ifndef ABSL_BASE_INTERNAL_SPINLOCK_H_
#define ABSL_BASE_INTERNAL_SPINLOCK_H_
#include <stdint.h>
#include <sys/types.h>
#include <atomic>
#include "absl/base/attributes.h"
#include "absl/base/const_init.h"
#include "absl/base/dynamic_annotations.h"
#include "absl/base/internal/low_level_scheduling.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/base/internal/scheduling_mode.h"
#include "absl/base/internal/tsan_mutex_interface.h"
#include "absl/base/macros.h"
#include "absl/base/port.h"
#include "absl/base/thread_annotations.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace base_internal {
class ABSL_LOCKABLE SpinLock {
public:
SpinLock() : lockword_(kSpinLockCooperative) {
ABSL_TSAN_MUTEX_CREATE(this, __tsan_mutex_not_static);
}
// Constructors that allow non-cooperative spinlocks to be created for use
// inside thread schedulers. Normal clients should not use these.
explicit SpinLock(base_internal::SchedulingMode mode);
// Constructor for global SpinLock instances. See absl/base/const_init.h.
constexpr SpinLock(absl::ConstInitType, base_internal::SchedulingMode mode)
: lockword_(IsCooperative(mode) ? kSpinLockCooperative : 0) {}
Export of internal Abseil changes -- 739f9fb80212c21c015fec473e9e29803a156ef9 by Derek Mauro <dmauro@google.com>: Define FlagStateInterface::~FlagStateInterface() in the translation unit in which it is actually declared Fixes #717 PiperOrigin-RevId: 319083605 -- 913ef1f23113268b22d636d3ae3b992862efdb1a by Derek Mauro <dmauro@google.com>: Fix ABSL_LOCK_RETURNED statement PiperOrigin-RevId: 319078667 -- a43b1413da1770d638147c73e7e1693cfaf869c7 by Derek Mauro <dmauro@google.com>: Fix redeclaration ‘absl::Cord::InlineRep::kMaxInline’, which differs in ‘constexpr’ Fixes #725 PiperOrigin-RevId: 319060910 -- 1ad7d491a80f6c9de78a6fc20f09b7765d224503 by Abseil Team <absl-team@google.com>: Make absl SpinLock trivially destructible when possible PiperOrigin-RevId: 319049456 -- 659ecad3578dfa669854a82279fa590002bdb37f by Derek Mauro <dmauro@google.com>: Remove the static initialization of global variables used by absl::Mutex as requested by Chromium PiperOrigin-RevId: 319031204 -- 609c491d8bb4f8bb3b44c5a4c0bee51c583df24c by Abseil Team <absl-team@google.com>: Add implementation of %a and %A to absl::StrFormat. Prior to this it just fell back to sprintf. PiperOrigin-RevId: 318888039 -- 5e8ae6392bcd135248aac14c4b9f2a5116868678 by Abseil Team <absl-team@google.com>: Google-internal changes only. PiperOrigin-RevId: 318857077 -- 4a2578e33e8442954e29e5f0380ddfcf0f033f0d by Greg Falcon <gfalcon@google.com>: Change of enum constants to accommodate internal change. PiperOrigin-RevId: 318844716 -- 4b578b102816260c213675759f4c15911735578a by Abseil Team <absl-team@google.com>: Internal change PiperOrigin-RevId: 318704453 -- 0ee82fd24d548b260c9229fa1f54571dae1dfa24 by Gennadiy Rozental <rogeeff@google.com>: Allow lookup of retired flags. At the moment we issue warning on attempt to find a retired flag. This way we can't even check if flag is retired without issuing the warning. With this change we will only issue the warning if one tries to access any functionality of retired flag but it's name "is retired" status, and type. PiperOrigin-RevId: 318605017 -- 3e35fe9b4c79f636fa328c59e2aabb93e29b7c99 by Abseil Team <absl-team@google.com>: Fix error return from InstallSymbolDecorator(). PiperOrigin-RevId: 318490405 -- ae46063f3eb2998cb961f62a359d932e5908a4bc by Abseil Team <absl-team@google.com>: Do not make copies of iterated collection elements into the loop variable. PiperOrigin-RevId: 318423139 -- d06a075a12aab5f6ab98474677ce50d588b21de3 by Abseil Team <absl-team@google.com>: add missing word making the error code better English PiperOrigin-RevId: 318335052 GitOrigin-RevId: 739f9fb80212c21c015fec473e9e29803a156ef9 Change-Id: Id77a0a4b1959036b00555deef40e82d51884fbc1
4 years ago
// For global SpinLock instances prefer trivial destructor when possible.
// Default but non-trivial destructor in some build configurations causes an
// extra static initializer.
#ifdef ABSL_INTERNAL_HAVE_TSAN_INTERFACE
Export of internal Abseil changes -- f012012ef78234a6a4585321b67d7b7c92ebc266 by Laramie Leavitt <lar@google.com>: Slight restructuring of absl/random/internal randen implementation. Convert round-keys.inc into randen_round_keys.cc file. Consistently use a 128-bit pointer type for internal method parameters. This allows simpler pointer arithmetic in C++ & permits removal of some constants and casts. Remove some redundancy in comments & constexpr variables. Specifically, all references to Randen algorithm parameters use RandenTraits; duplication in RandenSlow removed. PiperOrigin-RevId: 312190313 -- dc8b42e054046741e9ed65335bfdface997c6063 by Abseil Team <absl-team@google.com>: Internal change. PiperOrigin-RevId: 312167304 -- f13d248fafaf206492c1362c3574031aea3abaf7 by Matthew Brown <matthewbr@google.com>: Cleanup StrFormat extensions a little. PiperOrigin-RevId: 312166336 -- 9d9117589667afe2332bb7ad42bc967ca7c54502 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 312105213 -- 9a12b9b3aa0e59b8ee6cf9408ed0029045543a9b by Abseil Team <absl-team@google.com>: Complete IGNORE_TYPE macro renaming. PiperOrigin-RevId: 311999699 -- 64756f20d61021d999bd0d4c15e9ad3857382f57 by Gennadiy Rozental <rogeeff@google.com>: Switch to fixed bytes specific default value. This fixes the Abseil Flags for big endian platforms. PiperOrigin-RevId: 311844448 -- bdbe6b5b29791dbc3816ada1828458b3010ff1e9 by Laramie Leavitt <lar@google.com>: Change many distribution tests to use pcg_engine as a deterministic source of entropy. It's reasonable to test that the BitGen itself has good entropy, however when testing the cross product of all random distributions x all the architecture variations x all submitted changes results in a large number of tests. In order to account for these failures while still using good entropy requires that our allowed sigma need to account for all of these independent tests. Our current sigma values are too restrictive, and we see a lot of failures, so we have to either relax the sigma values or convert some of the statistical tests to use deterministic values. This changelist does the latter. PiperOrigin-RevId: 311840096 GitOrigin-RevId: f012012ef78234a6a4585321b67d7b7c92ebc266 Change-Id: Ic84886f38ff30d7d72c126e9b63c9a61eb729a1a
5 years ago
~SpinLock() { ABSL_TSAN_MUTEX_DESTROY(this, __tsan_mutex_not_static); }
Export of internal Abseil changes -- 739f9fb80212c21c015fec473e9e29803a156ef9 by Derek Mauro <dmauro@google.com>: Define FlagStateInterface::~FlagStateInterface() in the translation unit in which it is actually declared Fixes #717 PiperOrigin-RevId: 319083605 -- 913ef1f23113268b22d636d3ae3b992862efdb1a by Derek Mauro <dmauro@google.com>: Fix ABSL_LOCK_RETURNED statement PiperOrigin-RevId: 319078667 -- a43b1413da1770d638147c73e7e1693cfaf869c7 by Derek Mauro <dmauro@google.com>: Fix redeclaration ‘absl::Cord::InlineRep::kMaxInline’, which differs in ‘constexpr’ Fixes #725 PiperOrigin-RevId: 319060910 -- 1ad7d491a80f6c9de78a6fc20f09b7765d224503 by Abseil Team <absl-team@google.com>: Make absl SpinLock trivially destructible when possible PiperOrigin-RevId: 319049456 -- 659ecad3578dfa669854a82279fa590002bdb37f by Derek Mauro <dmauro@google.com>: Remove the static initialization of global variables used by absl::Mutex as requested by Chromium PiperOrigin-RevId: 319031204 -- 609c491d8bb4f8bb3b44c5a4c0bee51c583df24c by Abseil Team <absl-team@google.com>: Add implementation of %a and %A to absl::StrFormat. Prior to this it just fell back to sprintf. PiperOrigin-RevId: 318888039 -- 5e8ae6392bcd135248aac14c4b9f2a5116868678 by Abseil Team <absl-team@google.com>: Google-internal changes only. PiperOrigin-RevId: 318857077 -- 4a2578e33e8442954e29e5f0380ddfcf0f033f0d by Greg Falcon <gfalcon@google.com>: Change of enum constants to accommodate internal change. PiperOrigin-RevId: 318844716 -- 4b578b102816260c213675759f4c15911735578a by Abseil Team <absl-team@google.com>: Internal change PiperOrigin-RevId: 318704453 -- 0ee82fd24d548b260c9229fa1f54571dae1dfa24 by Gennadiy Rozental <rogeeff@google.com>: Allow lookup of retired flags. At the moment we issue warning on attempt to find a retired flag. This way we can't even check if flag is retired without issuing the warning. With this change we will only issue the warning if one tries to access any functionality of retired flag but it's name "is retired" status, and type. PiperOrigin-RevId: 318605017 -- 3e35fe9b4c79f636fa328c59e2aabb93e29b7c99 by Abseil Team <absl-team@google.com>: Fix error return from InstallSymbolDecorator(). PiperOrigin-RevId: 318490405 -- ae46063f3eb2998cb961f62a359d932e5908a4bc by Abseil Team <absl-team@google.com>: Do not make copies of iterated collection elements into the loop variable. PiperOrigin-RevId: 318423139 -- d06a075a12aab5f6ab98474677ce50d588b21de3 by Abseil Team <absl-team@google.com>: add missing word making the error code better English PiperOrigin-RevId: 318335052 GitOrigin-RevId: 739f9fb80212c21c015fec473e9e29803a156ef9 Change-Id: Id77a0a4b1959036b00555deef40e82d51884fbc1
4 years ago
#else
~SpinLock() = default;
#endif
Export of internal Abseil changes -- f012012ef78234a6a4585321b67d7b7c92ebc266 by Laramie Leavitt <lar@google.com>: Slight restructuring of absl/random/internal randen implementation. Convert round-keys.inc into randen_round_keys.cc file. Consistently use a 128-bit pointer type for internal method parameters. This allows simpler pointer arithmetic in C++ & permits removal of some constants and casts. Remove some redundancy in comments & constexpr variables. Specifically, all references to Randen algorithm parameters use RandenTraits; duplication in RandenSlow removed. PiperOrigin-RevId: 312190313 -- dc8b42e054046741e9ed65335bfdface997c6063 by Abseil Team <absl-team@google.com>: Internal change. PiperOrigin-RevId: 312167304 -- f13d248fafaf206492c1362c3574031aea3abaf7 by Matthew Brown <matthewbr@google.com>: Cleanup StrFormat extensions a little. PiperOrigin-RevId: 312166336 -- 9d9117589667afe2332bb7ad42bc967ca7c54502 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 312105213 -- 9a12b9b3aa0e59b8ee6cf9408ed0029045543a9b by Abseil Team <absl-team@google.com>: Complete IGNORE_TYPE macro renaming. PiperOrigin-RevId: 311999699 -- 64756f20d61021d999bd0d4c15e9ad3857382f57 by Gennadiy Rozental <rogeeff@google.com>: Switch to fixed bytes specific default value. This fixes the Abseil Flags for big endian platforms. PiperOrigin-RevId: 311844448 -- bdbe6b5b29791dbc3816ada1828458b3010ff1e9 by Laramie Leavitt <lar@google.com>: Change many distribution tests to use pcg_engine as a deterministic source of entropy. It's reasonable to test that the BitGen itself has good entropy, however when testing the cross product of all random distributions x all the architecture variations x all submitted changes results in a large number of tests. In order to account for these failures while still using good entropy requires that our allowed sigma need to account for all of these independent tests. Our current sigma values are too restrictive, and we see a lot of failures, so we have to either relax the sigma values or convert some of the statistical tests to use deterministic values. This changelist does the latter. PiperOrigin-RevId: 311840096 GitOrigin-RevId: f012012ef78234a6a4585321b67d7b7c92ebc266 Change-Id: Ic84886f38ff30d7d72c126e9b63c9a61eb729a1a
5 years ago
// Acquire this SpinLock.
inline void Lock() ABSL_EXCLUSIVE_LOCK_FUNCTION() {
ABSL_TSAN_MUTEX_PRE_LOCK(this, 0);
if (!TryLockImpl()) {
SlowLock();
}
ABSL_TSAN_MUTEX_POST_LOCK(this, 0, 0);
}
// Try to acquire this SpinLock without blocking and return true if the
// acquisition was successful. If the lock was not acquired, false is
// returned. If this SpinLock is free at the time of the call, TryLock
// will return true with high probability.
inline bool TryLock() ABSL_EXCLUSIVE_TRYLOCK_FUNCTION(true) {
ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_try_lock);
bool res = TryLockImpl();
ABSL_TSAN_MUTEX_POST_LOCK(
this, __tsan_mutex_try_lock | (res ? 0 : __tsan_mutex_try_lock_failed),
0);
return res;
}
// Release this SpinLock, which must be held by the calling thread.
inline void Unlock() ABSL_UNLOCK_FUNCTION() {
ABSL_TSAN_MUTEX_PRE_UNLOCK(this, 0);
uint32_t lock_value = lockword_.load(std::memory_order_relaxed);
lock_value = lockword_.exchange(lock_value & kSpinLockCooperative,
std::memory_order_release);
if ((lock_value & kSpinLockDisabledScheduling) != 0) {
base_internal::SchedulingGuard::EnableRescheduling(true);
}
if ((lock_value & kWaitTimeMask) != 0) {
// Collect contentionz profile info, and speed the wakeup of any waiter.
// The wait_cycles value indicates how long this thread spent waiting
// for the lock.
SlowUnlock(lock_value);
}
ABSL_TSAN_MUTEX_POST_UNLOCK(this, 0);
}
// Determine if the lock is held. When the lock is held by the invoking
// thread, true will always be returned. Intended to be used as
// CHECK(lock.IsHeld()).
inline bool IsHeld() const {
return (lockword_.load(std::memory_order_relaxed) & kSpinLockHeld) != 0;
}
protected:
// These should not be exported except for testing.
// Store number of cycles between wait_start_time and wait_end_time in a
// lock value.
static uint32_t EncodeWaitCycles(int64_t wait_start_time,
int64_t wait_end_time);
// Extract number of wait cycles in a lock value.
static uint64_t DecodeWaitCycles(uint32_t lock_value);
// Provide access to protected method above. Use for testing only.
friend struct SpinLockTest;
private:
// lockword_ is used to store the following:
//
// bit[0] encodes whether a lock is being held.
// bit[1] encodes whether a lock uses cooperative scheduling.
// bit[2] encodes whether the current lock holder disabled scheduling when
// acquiring the lock. Only set when kSpinLockHeld is also set.
Export of internal Abseil changes -- f012012ef78234a6a4585321b67d7b7c92ebc266 by Laramie Leavitt <lar@google.com>: Slight restructuring of absl/random/internal randen implementation. Convert round-keys.inc into randen_round_keys.cc file. Consistently use a 128-bit pointer type for internal method parameters. This allows simpler pointer arithmetic in C++ & permits removal of some constants and casts. Remove some redundancy in comments & constexpr variables. Specifically, all references to Randen algorithm parameters use RandenTraits; duplication in RandenSlow removed. PiperOrigin-RevId: 312190313 -- dc8b42e054046741e9ed65335bfdface997c6063 by Abseil Team <absl-team@google.com>: Internal change. PiperOrigin-RevId: 312167304 -- f13d248fafaf206492c1362c3574031aea3abaf7 by Matthew Brown <matthewbr@google.com>: Cleanup StrFormat extensions a little. PiperOrigin-RevId: 312166336 -- 9d9117589667afe2332bb7ad42bc967ca7c54502 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 312105213 -- 9a12b9b3aa0e59b8ee6cf9408ed0029045543a9b by Abseil Team <absl-team@google.com>: Complete IGNORE_TYPE macro renaming. PiperOrigin-RevId: 311999699 -- 64756f20d61021d999bd0d4c15e9ad3857382f57 by Gennadiy Rozental <rogeeff@google.com>: Switch to fixed bytes specific default value. This fixes the Abseil Flags for big endian platforms. PiperOrigin-RevId: 311844448 -- bdbe6b5b29791dbc3816ada1828458b3010ff1e9 by Laramie Leavitt <lar@google.com>: Change many distribution tests to use pcg_engine as a deterministic source of entropy. It's reasonable to test that the BitGen itself has good entropy, however when testing the cross product of all random distributions x all the architecture variations x all submitted changes results in a large number of tests. In order to account for these failures while still using good entropy requires that our allowed sigma need to account for all of these independent tests. Our current sigma values are too restrictive, and we see a lot of failures, so we have to either relax the sigma values or convert some of the statistical tests to use deterministic values. This changelist does the latter. PiperOrigin-RevId: 311840096 GitOrigin-RevId: f012012ef78234a6a4585321b67d7b7c92ebc266 Change-Id: Ic84886f38ff30d7d72c126e9b63c9a61eb729a1a
5 years ago
// bit[3:31] encodes time a lock spent on waiting as a 29-bit unsigned int.
// This is set by the lock holder to indicate how long it waited on
// the lock before eventually acquiring it. The number of cycles is
// encoded as a 29-bit unsigned int, or in the case that the current
// holder did not wait but another waiter is queued, the LSB
// (kSpinLockSleeper) is set. The implementation does not explicitly
// track the number of queued waiters beyond this. It must always be
// assumed that waiters may exist if the current holder was required to
// queue.
//
// Invariant: if the lock is not held, the value is either 0 or
// kSpinLockCooperative.
Export of internal Abseil changes -- f012012ef78234a6a4585321b67d7b7c92ebc266 by Laramie Leavitt <lar@google.com>: Slight restructuring of absl/random/internal randen implementation. Convert round-keys.inc into randen_round_keys.cc file. Consistently use a 128-bit pointer type for internal method parameters. This allows simpler pointer arithmetic in C++ & permits removal of some constants and casts. Remove some redundancy in comments & constexpr variables. Specifically, all references to Randen algorithm parameters use RandenTraits; duplication in RandenSlow removed. PiperOrigin-RevId: 312190313 -- dc8b42e054046741e9ed65335bfdface997c6063 by Abseil Team <absl-team@google.com>: Internal change. PiperOrigin-RevId: 312167304 -- f13d248fafaf206492c1362c3574031aea3abaf7 by Matthew Brown <matthewbr@google.com>: Cleanup StrFormat extensions a little. PiperOrigin-RevId: 312166336 -- 9d9117589667afe2332bb7ad42bc967ca7c54502 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 312105213 -- 9a12b9b3aa0e59b8ee6cf9408ed0029045543a9b by Abseil Team <absl-team@google.com>: Complete IGNORE_TYPE macro renaming. PiperOrigin-RevId: 311999699 -- 64756f20d61021d999bd0d4c15e9ad3857382f57 by Gennadiy Rozental <rogeeff@google.com>: Switch to fixed bytes specific default value. This fixes the Abseil Flags for big endian platforms. PiperOrigin-RevId: 311844448 -- bdbe6b5b29791dbc3816ada1828458b3010ff1e9 by Laramie Leavitt <lar@google.com>: Change many distribution tests to use pcg_engine as a deterministic source of entropy. It's reasonable to test that the BitGen itself has good entropy, however when testing the cross product of all random distributions x all the architecture variations x all submitted changes results in a large number of tests. In order to account for these failures while still using good entropy requires that our allowed sigma need to account for all of these independent tests. Our current sigma values are too restrictive, and we see a lot of failures, so we have to either relax the sigma values or convert some of the statistical tests to use deterministic values. This changelist does the latter. PiperOrigin-RevId: 311840096 GitOrigin-RevId: f012012ef78234a6a4585321b67d7b7c92ebc266 Change-Id: Ic84886f38ff30d7d72c126e9b63c9a61eb729a1a
5 years ago
static constexpr uint32_t kSpinLockHeld = 1;
static constexpr uint32_t kSpinLockCooperative = 2;
static constexpr uint32_t kSpinLockDisabledScheduling = 4;
static constexpr uint32_t kSpinLockSleeper = 8;
// Includes kSpinLockSleeper.
static constexpr uint32_t kWaitTimeMask =
~(kSpinLockHeld | kSpinLockCooperative | kSpinLockDisabledScheduling);
// Returns true if the provided scheduling mode is cooperative.
static constexpr bool IsCooperative(
base_internal::SchedulingMode scheduling_mode) {
return scheduling_mode == base_internal::SCHEDULE_COOPERATIVE_AND_KERNEL;
}
uint32_t TryLockInternal(uint32_t lock_value, uint32_t wait_cycles);
void SlowLock() ABSL_ATTRIBUTE_COLD;
void SlowUnlock(uint32_t lock_value) ABSL_ATTRIBUTE_COLD;
uint32_t SpinLoop();
inline bool TryLockImpl() {
uint32_t lock_value = lockword_.load(std::memory_order_relaxed);
return (TryLockInternal(lock_value, 0) & kSpinLockHeld) == 0;
}
std::atomic<uint32_t> lockword_;
SpinLock(const SpinLock&) = delete;
SpinLock& operator=(const SpinLock&) = delete;
};
// Corresponding locker object that arranges to acquire a spinlock for
// the duration of a C++ scope.
class ABSL_SCOPED_LOCKABLE SpinLockHolder {
public:
inline explicit SpinLockHolder(SpinLock* l) ABSL_EXCLUSIVE_LOCK_FUNCTION(l)
: lock_(l) {
l->Lock();
}
inline ~SpinLockHolder() ABSL_UNLOCK_FUNCTION() { lock_->Unlock(); }
SpinLockHolder(const SpinLockHolder&) = delete;
SpinLockHolder& operator=(const SpinLockHolder&) = delete;
private:
SpinLock* lock_;
};
// Register a hook for profiling support.
//
// The function pointer registered here will be called whenever a spinlock is
// contended. The callback is given an opaque handle to the contended spinlock
// and the number of wait cycles. This is thread-safe, but only a single
// profiler can be registered. It is an error to call this function multiple
// times with different arguments.
void RegisterSpinLockProfiler(void (*fn)(const void* lock,
int64_t wait_cycles));
//------------------------------------------------------------------------------
// Public interface ends here.
//------------------------------------------------------------------------------
// If (result & kSpinLockHeld) == 0, then *this was successfully locked.
// Otherwise, returns last observed value for lockword_.
inline uint32_t SpinLock::TryLockInternal(uint32_t lock_value,
uint32_t wait_cycles) {
if ((lock_value & kSpinLockHeld) != 0) {
return lock_value;
}
uint32_t sched_disabled_bit = 0;
if ((lock_value & kSpinLockCooperative) == 0) {
// For non-cooperative locks we must make sure we mark ourselves as
// non-reschedulable before we attempt to CompareAndSwap.
if (base_internal::SchedulingGuard::DisableRescheduling()) {
sched_disabled_bit = kSpinLockDisabledScheduling;
}
}
if (!lockword_.compare_exchange_strong(
lock_value,
kSpinLockHeld | lock_value | wait_cycles | sched_disabled_bit,
std::memory_order_acquire, std::memory_order_relaxed)) {
base_internal::SchedulingGuard::EnableRescheduling(sched_disabled_bit != 0);
}
return lock_value;
}
} // namespace base_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_BASE_INTERNAL_SPINLOCK_H_