| // 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 |