Disk cache: Remove all non essential synchronization from the cache destructor.

net/disk_cache/in_flight_io.cc

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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 "net/disk_cache/in_flight_io.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 
 namespace disk_cache {
 
 BackgroundIO::BackgroundIO(InFlightIO* controller)
-    : controller_(controller), result_(-1), io_completed_(true, false) {
+    : result_(-1), io_completed_(true, false), controller_(controller) {
 }
 
 // Runs on the primary thread.
 void BackgroundIO::OnIOSignalled() {
   if (controller_)
     controller_->InvokeCallback(this, false);
 }
 
 void BackgroundIO::Cancel() {
+  // controller_ may be in use from the background thread at this time.
+  base::AutoLock lock(controller_lock_);
   DCHECK(controller_);
   controller_ = NULL;
 }
 
 BackgroundIO::~BackgroundIO() {}
 
-// Runs on the background thread.
-void BackgroundIO::NotifyController() {
-  controller_->OnIOComplete(this);
-}
-
 // ---------------------------------------------------------------------------
 
 InFlightIO::InFlightIO()
     : callback_thread_(base::MessageLoopProxy::current()),
       running_(false), single_thread_(false) {
 }
 
 InFlightIO::~InFlightIO() {
 }
 
+// Runs on the background thread.
+void BackgroundIO::NotifyController() {
+  base::AutoLock lock(controller_lock_);
+  if (controller_)
+    controller_->OnIOComplete(this);
+}
+
 void InFlightIO::WaitForPendingIO() {
   while (!io_list_.empty()) {
     // Block the current thread until all pending IO completes.
     IOList::iterator it = io_list_.begin();
     InvokeCallback(*it, true);
   }
 }
 
+void InFlightIO::DropPendingIO() {
+  while (!io_list_.empty()) {
+    IOList::iterator it = io_list_.begin();
+    BackgroundIO* operation = *it;
+    operation->Cancel();
+    DCHECK(io_list_.find(operation) != io_list_.end());
+    io_list_.erase(make_scoped_refptr(operation));
+  }
+}
+
 // Runs on a background thread.
 void InFlightIO::OnIOComplete(BackgroundIO* operation) {
 #ifndef NDEBUG
   if (callback_thread_->BelongsToCurrentThread()) {
     DCHECK(single_thread_ || !running_);
     single_thread_ = true;
   }
 #endif
 
   callback_thread_->PostTask(FROM_HERE,
@@ skipping 17 matching lines @@
   OnOperationComplete(operation, cancel_task);
 }
 
 // Runs on the primary thread.
 void InFlightIO::OnOperationPosted(BackgroundIO* operation) {
   DCHECK(callback_thread_->BelongsToCurrentThread());
   io_list_.insert(make_scoped_refptr(operation));
 }
 
 }  // namespace disk_cache