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// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/lock_impl.h"
#include "base/logging.h"
// NOTE: Although windows critical sections support recursive locks, we do not
// allow this, and we will commonly fire a DCHECK() if a thread attempts to
// acquire the lock a second time (while already holding it).
LockImpl::LockImpl() {
#ifndef NDEBUG
recursion_count_shadow_ = 0;
recursion_used_ = false;
owning_thread_id_ = 0;
#endif // NDEBUG
// The second parameter is the spin count, for short-held locks it avoid the
// contending thread from going to sleep which helps performance greatly.
::InitializeCriticalSectionAndSpinCount(&os_lock_, 2000);
}
LockImpl::~LockImpl() {
::DeleteCriticalSection(&os_lock_);
}
bool LockImpl::Try() {
if (::TryEnterCriticalSection(&os_lock_) != FALSE) {
#ifndef NDEBUG
// ONLY access data after locking.
owning_thread_id_ = PlatformThread::CurrentId();
DCHECK_NE(owning_thread_id_, 0);
recursion_count_shadow_++;
if (2 == recursion_count_shadow_ && !recursion_used_) {
recursion_used_ = true;
DCHECK(false); // Catch accidental redundant lock acquisition.
}
#endif
return true;
}
return false;
}
void LockImpl::Lock() {
::EnterCriticalSection(&os_lock_);
#ifndef NDEBUG
// ONLY access data after locking.
owning_thread_id_ = PlatformThread::CurrentId();
DCHECK_NE(owning_thread_id_, 0);
recursion_count_shadow_++;
if (2 == recursion_count_shadow_ && !recursion_used_) {
recursion_used_ = true;
DCHECK(false); // Catch accidental redundant lock acquisition.
}
#endif // NDEBUG
}
void LockImpl::Unlock() {
#ifndef NDEBUG
--recursion_count_shadow_; // ONLY access while lock is still held.
DCHECK(0 <= recursion_count_shadow_);
owning_thread_id_ = 0;
#endif // NDEBUG
::LeaveCriticalSection(&os_lock_);
}
// In non-debug builds, this method is declared as an empty inline method.
#ifndef NDEBUG
void LockImpl::AssertAcquired() const {
DCHECK(recursion_count_shadow_ > 0);
DCHECK_EQ(owning_thread_id_, PlatformThread::CurrentId());
}
#endif
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