blob: 08acb13317c787ebc5ac82cafc58c261617cafff [file] [log] [blame]
/*
* Copyright 2015 The WebRTC Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "webrtc/rtc_base/criticalsection.h"
#include "webrtc/rtc_base/checks.h"
#include "webrtc/rtc_base/platform_thread.h"
// TODO(tommi): Split this file up to per-platform implementation files.
namespace rtc {
CriticalSection::CriticalSection() {
#if defined(WEBRTC_WIN)
InitializeCriticalSection(&crit_);
#elif defined(WEBRTC_POSIX)
# if defined(WEBRTC_MAC) && !USE_NATIVE_MUTEX_ON_MAC
lock_queue_ = 0;
owning_thread_ = 0;
recursion_ = 0;
semaphore_ = dispatch_semaphore_create(0);
# else
pthread_mutexattr_t mutex_attribute;
pthread_mutexattr_init(&mutex_attribute);
pthread_mutexattr_settype(&mutex_attribute, PTHREAD_MUTEX_RECURSIVE);
pthread_mutex_init(&mutex_, &mutex_attribute);
pthread_mutexattr_destroy(&mutex_attribute);
# endif
CS_DEBUG_CODE(thread_ = 0);
CS_DEBUG_CODE(recursion_count_ = 0);
RTC_UNUSED(thread_);
RTC_UNUSED(recursion_count_);
#else
# error Unsupported platform.
#endif
}
CriticalSection::~CriticalSection() {
#if defined(WEBRTC_WIN)
DeleteCriticalSection(&crit_);
#elif defined(WEBRTC_POSIX)
# if defined(WEBRTC_MAC) && !USE_NATIVE_MUTEX_ON_MAC
dispatch_release(semaphore_);
# else
pthread_mutex_destroy(&mutex_);
# endif
#else
# error Unsupported platform.
#endif
}
void CriticalSection::Enter() const EXCLUSIVE_LOCK_FUNCTION() {
#if defined(WEBRTC_WIN)
EnterCriticalSection(&crit_);
#elif defined(WEBRTC_POSIX)
# if defined(WEBRTC_MAC) && !USE_NATIVE_MUTEX_ON_MAC
int spin = 3000;
PlatformThreadRef self = CurrentThreadRef();
bool have_lock = false;
do {
// Instead of calling TryEnter() in this loop, we do two interlocked
// operations, first a read-only one in order to avoid affecting the lock
// cache-line while spinning, in case another thread is using the lock.
if (!IsThreadRefEqual(owning_thread_, self)) {
if (AtomicOps::AcquireLoad(&lock_queue_) == 0) {
if (AtomicOps::CompareAndSwap(&lock_queue_, 0, 1) == 0) {
have_lock = true;
break;
}
}
} else {
AtomicOps::Increment(&lock_queue_);
have_lock = true;
break;
}
sched_yield();
} while (--spin);
if (!have_lock && AtomicOps::Increment(&lock_queue_) > 1) {
// Owning thread cannot be the current thread since TryEnter() would
// have succeeded.
RTC_DCHECK(!IsThreadRefEqual(owning_thread_, self));
// Wait for the lock to become available.
dispatch_semaphore_wait(semaphore_, DISPATCH_TIME_FOREVER);
RTC_DCHECK(owning_thread_ == 0);
RTC_DCHECK(!recursion_);
}
owning_thread_ = self;
++recursion_;
# else
pthread_mutex_lock(&mutex_);
# endif
# if CS_DEBUG_CHECKS
if (!recursion_count_) {
RTC_DCHECK(!thread_);
thread_ = CurrentThreadRef();
} else {
RTC_DCHECK(CurrentThreadIsOwner());
}
++recursion_count_;
# endif
#else
# error Unsupported platform.
#endif
}
bool CriticalSection::TryEnter() const EXCLUSIVE_TRYLOCK_FUNCTION(true) {
#if defined(WEBRTC_WIN)
return TryEnterCriticalSection(&crit_) != FALSE;
#elif defined(WEBRTC_POSIX)
# if defined(WEBRTC_MAC) && !USE_NATIVE_MUTEX_ON_MAC
if (!IsThreadRefEqual(owning_thread_, CurrentThreadRef())) {
if (AtomicOps::CompareAndSwap(&lock_queue_, 0, 1) != 0)
return false;
owning_thread_ = CurrentThreadRef();
RTC_DCHECK(!recursion_);
} else {
AtomicOps::Increment(&lock_queue_);
}
++recursion_;
# else
if (pthread_mutex_trylock(&mutex_) != 0)
return false;
# endif
# if CS_DEBUG_CHECKS
if (!recursion_count_) {
RTC_DCHECK(!thread_);
thread_ = CurrentThreadRef();
} else {
RTC_DCHECK(CurrentThreadIsOwner());
}
++recursion_count_;
# endif
return true;
#else
# error Unsupported platform.
#endif
}
void CriticalSection::Leave() const UNLOCK_FUNCTION() {
RTC_DCHECK(CurrentThreadIsOwner());
#if defined(WEBRTC_WIN)
LeaveCriticalSection(&crit_);
#elif defined(WEBRTC_POSIX)
# if CS_DEBUG_CHECKS
--recursion_count_;
RTC_DCHECK(recursion_count_ >= 0);
if (!recursion_count_)
thread_ = 0;
# endif
# if defined(WEBRTC_MAC) && !USE_NATIVE_MUTEX_ON_MAC
RTC_DCHECK(IsThreadRefEqual(owning_thread_, CurrentThreadRef()));
RTC_DCHECK_GE(recursion_, 0);
--recursion_;
if (!recursion_)
owning_thread_ = 0;
if (AtomicOps::Decrement(&lock_queue_) > 0 && !recursion_)
dispatch_semaphore_signal(semaphore_);
# else
pthread_mutex_unlock(&mutex_);
# endif
#else
# error Unsupported platform.
#endif
}
bool CriticalSection::CurrentThreadIsOwner() const {
#if defined(WEBRTC_WIN)
// OwningThread has type HANDLE but actually contains the Thread ID:
// http://stackoverflow.com/questions/12675301/why-is-the-owningthread-member-of-critical-section-of-type-handle-when-it-is-de
// Converting through size_t avoids the VS 2015 warning C4312: conversion from
// 'type1' to 'type2' of greater size
return crit_.OwningThread ==
reinterpret_cast<HANDLE>(static_cast<size_t>(GetCurrentThreadId()));
#elif defined(WEBRTC_POSIX)
# if CS_DEBUG_CHECKS
return IsThreadRefEqual(thread_, CurrentThreadRef());
# else
return true;
# endif // CS_DEBUG_CHECKS
#else
# error Unsupported platform.
#endif
}
CritScope::CritScope(const CriticalSection* cs) : cs_(cs) { cs_->Enter(); }
CritScope::~CritScope() { cs_->Leave(); }
TryCritScope::TryCritScope(const CriticalSection* cs)
: cs_(cs), locked_(cs->TryEnter()) {
CS_DEBUG_CODE(lock_was_called_ = false);
RTC_UNUSED(lock_was_called_);
}
TryCritScope::~TryCritScope() {
CS_DEBUG_CODE(RTC_DCHECK(lock_was_called_));
if (locked_)
cs_->Leave();
}
bool TryCritScope::locked() const {
CS_DEBUG_CODE(lock_was_called_ = true);
return locked_;
}
void GlobalLockPod::Lock() {
#if !defined(WEBRTC_WIN) && (!defined(WEBRTC_MAC) || USE_NATIVE_MUTEX_ON_MAC)
const struct timespec ts_null = {0};
#endif
while (AtomicOps::CompareAndSwap(&lock_acquired, 0, 1)) {
#if defined(WEBRTC_WIN)
::Sleep(0);
#elif defined(WEBRTC_MAC) && !USE_NATIVE_MUTEX_ON_MAC
sched_yield();
#else
nanosleep(&ts_null, nullptr);
#endif
}
}
void GlobalLockPod::Unlock() {
int old_value = AtomicOps::CompareAndSwap(&lock_acquired, 1, 0);
RTC_DCHECK_EQ(1, old_value) << "Unlock called without calling Lock first";
}
GlobalLock::GlobalLock() {
lock_acquired = 0;
}
GlobalLockScope::GlobalLockScope(GlobalLockPod* lock)
: lock_(lock) {
lock_->Lock();
}
GlobalLockScope::~GlobalLockScope() {
lock_->Unlock();
}
} // namespace rtc