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