Worker changes to prepare for lock-free shutdown.

chrome/browser/sync/glue/browser_thread_model_worker.cc

 // 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 "chrome/browser/sync/glue/browser_thread_model_worker.h"
 
 #include "base/bind.h"
 #include "base/synchronization/waitable_event.h"
 #include "content/public/browser/browser_thread.h"
 
 using base::WaitableEvent;
 using content::BrowserThread;
 
 namespace browser_sync {
 
 BrowserThreadModelWorker::BrowserThreadModelWorker(
-    BrowserThread::ID thread, syncer::ModelSafeGroup group)
-    : thread_(thread), group_(group) {
+    BrowserThread::ID thread, syncer::ModelSafeGroup group,
+    syncer::WorkerLoopDestructionObserver* observer)
+    : ModelSafeWorker(observer),
+      thread_(thread), group_(group) {
 }
 
-syncer::SyncerError BrowserThreadModelWorker::DoWorkAndWaitUntilDone(
-    const syncer::WorkCallback& work) {
+syncer::SyncerError BrowserThreadModelWorker::DoWorkAndWaitUntilDoneImpl(
+    const syncer::WorkCallback& work,
+    base::WaitableEvent* done) {
   syncer::SyncerError error = syncer::UNSET;
   if (BrowserThread::CurrentlyOn(thread_)) {
     DLOG(WARNING) << "Already on thread " << thread_;
     return work.Run();
   }
-  WaitableEvent done(false, false);
+
   if (!BrowserThread::PostTask(
       thread_,
       FROM_HERE,
-      base::Bind(&BrowserThreadModelWorker::CallDoWorkAndSignalTask, this,
-                 work, &done, &error))) {
+      base::Bind(&BrowserThreadModelWorker::CallDoWorkAndSignalTask,
+                 this, work, done, &error))) {
     DLOG(WARNING) << "Failed to post task to thread " << thread_;
     error = syncer::CANNOT_DO_WORK;
     return error;
   }
-  done.Wait();
+  done->Wait();
   return error;
 }
 
 syncer::ModelSafeGroup BrowserThreadModelWorker::GetModelSafeGroup() {
   return group_;
 }
 
 BrowserThreadModelWorker::~BrowserThreadModelWorker() {}
 
+void BrowserThreadModelWorker::RegisterForLoopDestruction() {
+  if (BrowserThread::CurrentlyOn(thread_)) {
+    MessageLoop::current()->AddDestructionObserver(this);
+  } else {
+    BrowserThread::PostTask(
+        thread_, FROM_HERE,
+        Bind(&BrowserThreadModelWorker::RegisterForLoopDestruction, this));
+  }
+}
+
 void BrowserThreadModelWorker::CallDoWorkAndSignalTask(
     const syncer::WorkCallback& work,
     WaitableEvent* done,
     syncer::SyncerError* error) {
   DCHECK(BrowserThread::CurrentlyOn(thread_));
-  *error = work.Run();
+  if (!IsStopped())
+    *error = work.Run();
   done->Signal();
 }
 
-DatabaseModelWorker::DatabaseModelWorker()
-    : BrowserThreadModelWorker(BrowserThread::DB, syncer::GROUP_DB) {
+DatabaseModelWorker::DatabaseModelWorker(
+    syncer::WorkerLoopDestructionObserver* observer)
+    : BrowserThreadModelWorker(BrowserThread::DB, syncer::GROUP_DB, observer) {
 }
 
 void DatabaseModelWorker::CallDoWorkAndSignalTask(
     const syncer::WorkCallback& work,
     WaitableEvent* done,
     syncer::SyncerError* error) {
   BrowserThreadModelWorker::CallDoWorkAndSignalTask(work, done, error);
 }
 
 DatabaseModelWorker::~DatabaseModelWorker() {}
 
-FileModelWorker::FileModelWorker()
-    : BrowserThreadModelWorker(BrowserThread::FILE, syncer::GROUP_FILE) {
+FileModelWorker::FileModelWorker(
+    syncer::WorkerLoopDestructionObserver* observer)
+    : BrowserThreadModelWorker(BrowserThread::FILE, syncer::GROUP_FILE,
+                               observer) {
 }
 
 void FileModelWorker::CallDoWorkAndSignalTask(
     const syncer::WorkCallback& work,
     WaitableEvent* done,
     syncer::SyncerError* error) {
   BrowserThreadModelWorker::CallDoWorkAndSignalTask(work, done, error);
 }
 
 FileModelWorker::~FileModelWorker() {}
 
 }  // namespace browser_sync