|  | // Copyright (c) 2011 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/synchronization/lock_impl.h" | 
|  |  | 
|  | #include "base/debug/activity_tracker.h" | 
|  |  | 
|  | #include <windows.h> | 
|  |  | 
|  | namespace base { | 
|  | namespace internal { | 
|  |  | 
|  | LockImpl::LockImpl() : native_handle_(SRWLOCK_INIT) {} | 
|  |  | 
|  | LockImpl::~LockImpl() = default; | 
|  |  | 
|  | bool LockImpl::Try() { | 
|  | return !!::TryAcquireSRWLockExclusive( | 
|  | reinterpret_cast<PSRWLOCK>(&native_handle_)); | 
|  | } | 
|  |  | 
|  | void LockImpl::Lock() { | 
|  | // The ScopedLockAcquireActivity below is relatively expensive and so its | 
|  | // actions can become significant due to the very large number of locks | 
|  | // that tend to be used throughout the build. To avoid this cost in the | 
|  | // vast majority of the calls, simply "try" the lock first and only do the | 
|  | // (tracked) blocking call if that fails. Since "try" itself is a system | 
|  | // call, and thus also somewhat expensive, don't bother with it unless | 
|  | // tracking is actually enabled. | 
|  | if (base::debug::GlobalActivityTracker::IsEnabled()) | 
|  | if (Try()) | 
|  | return; | 
|  |  | 
|  | base::debug::ScopedLockAcquireActivity lock_activity(this); | 
|  | ::AcquireSRWLockExclusive(reinterpret_cast<PSRWLOCK>(&native_handle_)); | 
|  | } | 
|  |  | 
|  | }  // namespace internal | 
|  | }  // namespace base |