Worker changes to prepare for lock-free shutdown.

chrome/browser/sync/glue/ui_model_worker.h

 // 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.
 
 #ifndef CHROME_BROWSER_SYNC_GLUE_UI_MODEL_WORKER_H_
 #define CHROME_BROWSER_SYNC_GLUE_UI_MODEL_WORKER_H_
 
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/synchronization/condition_variable.h"
 #include "base/synchronization/lock.h"
 #include "sync/internal_api/public/engine/model_safe_worker.h"
 #include "sync/internal_api/public/util/unrecoverable_error_info.h"
 
 namespace browser_sync {
 
 // A syncer::ModelSafeWorker for UI models (e.g. bookmarks) that
 // accepts work requests from the syncapi that need to be fulfilled
 // from the MessageLoop home to the native model.
 //
 // Lifetime note: Instances of this class will generally be owned by the
 // SyncerThread. When the SyncerThread _object_ is destroyed, the
 // UIModelWorker will be destroyed. The SyncerThread object is destroyed
 // after the actual syncer pthread has exited.
 class UIModelWorker : public syncer::ModelSafeWorker {
  public:
-  UIModelWorker();
+  explicit UIModelWorker(syncer::WorkerLoopDestructionObserver* observer);
 
   // Called by the UI thread on shutdown of the sync service. Blocks until
   // the UIModelWorker has safely met termination conditions, namely that
   // no task scheduled by CallDoWorkFromModelSafeThreadAndWait remains un-
   // processed and that syncapi will not schedule any further work for us to do.
   void Stop();
 
   // syncer::ModelSafeWorker implementation. Called on syncapi SyncerThread.
-  virtual syncer::SyncerError DoWorkAndWaitUntilDone(
-      const syncer::WorkCallback& work) OVERRIDE;
+  virtual void RegisterForLoopDestruction() OVERRIDE;
   virtual syncer::ModelSafeGroup GetModelSafeGroup() OVERRIDE;
 
   // Upon receiving this idempotent call, the syncer::ModelSafeWorker can
   // assume no work will ever be scheduled again from now on. If it has any work
   // that it has not yet completed, it must make sure to run it as soon as
   // possible as the Syncer is trying to shut down. Called from the CoreThread.
   void OnSyncerShutdownComplete();
 
   // Callback from |pending_work_| to notify us that it has been run.
   // Called on ui loop.
   void OnTaskCompleted() { pending_work_.Reset(); }
 
+ protected:
+  virtual syncer::SyncerError DoWorkAndWaitUntilDoneImpl(
+      const syncer::WorkCallback& work,
+      base::WaitableEvent* work_done) OVERRIDE;
+
  private:
   // The life-cycle of a UIModelWorker in three states.
   enum State {
     // We hit the ground running in this state and remain until
     // the UI loop calls Stop().
     WORKING,
     // Stop() sequence has been initiated, but we have not received word that
     // the SyncerThread has terminated and doesn't need us anymore. Since the
     // UI MessageLoop is not running at this point, we manually process any
     // last pending_task_ that the Syncer throws at us, effectively dedicating
     // the UI thread to terminating the Syncer.
     RUNNING_MANUAL_SHUTDOWN_PUMP,
     // We have come to a complete stop, no scheduled work remains, and no work
     // will be scheduled from now until our destruction.
     STOPPED,
   };
 
   virtual ~UIModelWorker();
 
+  void CallDoWorkAndSignalCallback(const syncer::WorkCallback& work,
+                                   base::WaitableEvent* work_done,
+                                   syncer::SyncerError* error_info);
+
   // This is set by the UI thread, but is not explicitly thread safe, so only
   // read this value from other threads when you know it is absolutely safe.
   State state_;
 
   // We keep a reference to any task we have scheduled so we can gracefully
   // force them to run if the syncer is trying to shutdown.
   base::Closure pending_work_;
 
   // Set by the SyncCoreThread when Syncapi shutdown has completed and the
   // SyncerThread has terminated, so no more work will be scheduled. Read by
@@ skipping 14 matching lines @@
   // SyncerThread has terminated. We only care about (1) when we are in Stop(),
   // because we have to manually Run() the task.
   base::ConditionVariable syncapi_event_;
 
   DISALLOW_COPY_AND_ASSIGN(UIModelWorker);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_UI_MODEL_WORKER_H_