Support for multiple sync ModelSafeWorkers....

chrome/browser/sync/glue/bookmark_model_worker.cc

-// Copyright (c) 2006-2008 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/bookmark_model_worker.h"
-
-#include "base/message_loop.h"
-#include "base/waitable_event.h"
-
-namespace browser_sync {
-
-void BookmarkModelWorker::CallDoWorkFromModelSafeThreadAndWait(
-    ModelSafeWorkerInterface::Visitor* visitor) {
-  // It is possible this gets called when we are in the STOPPING state, because
-  // the UI loop has initiated shutdown but the syncer hasn't got the memo yet.
-  // This is fine, the work will get scheduled and run normally or run by our
-  // code handling this case in Stop().
-  DCHECK_NE(state_, STOPPED);
-  if (state_ == STOPPED)
-    return;
-  if (MessageLoop::current() == bookmark_model_loop_) {
-    DLOG(WARNING) << "CallDoWorkFromModelSafeThreadAndWait called from "
-      << "bookmark_model_loop_. Probably a nested invocation?";
-    visitor->DoWork();
-    return;
-  }
-
-  // Create an unsignaled event to wait on.
-  base::WaitableEvent work_done(false, false);
-  {
-    // We lock only to avoid PostTask'ing a NULL pending_work_ (because it
-    // could get Run() in Stop() and call OnTaskCompleted before we post).
-    // The task is owned by the message loop as per usual.
-    AutoLock lock(lock_);
-    DCHECK(!pending_work_);
-    pending_work_ = new CallDoWorkAndSignalTask(visitor, &work_done, this);
-    bookmark_model_loop_->PostTask(FROM_HERE, pending_work_);
-  }
-  syncapi_event_.Signal();  // Notify that the syncapi produced work for us.
-  work_done.Wait();
-}
-
-BookmarkModelWorker::~BookmarkModelWorker() {
-  DCHECK_EQ(state_, STOPPED);
-}
-
-void BookmarkModelWorker::OnSyncerShutdownComplete() {
-  AutoLock lock(lock_);
-  // The SyncerThread has terminated and we are no longer needed by syncapi.
-  // The UI loop initiated shutdown and is (or will be) waiting in Stop().
-  // We could either be WORKING or RUNNING_MANUAL_SHUTDOWN_PUMP, depending
-  // on where we timeslice the UI thread in Stop; but we can't be STOPPED,
-  // because that would imply OnSyncerShutdownComplete already signaled.
-  DCHECK_NE(state_, STOPPED);
-
-  syncapi_has_shutdown_ = true;
-  syncapi_event_.Signal();
-}
-
-void BookmarkModelWorker::Stop() {
-  DCHECK_EQ(MessageLoop::current(), bookmark_model_loop_);
-
-  AutoLock lock(lock_);
-  DCHECK_EQ(state_, WORKING);
-
-  // We're on our own now, the beloved UI MessageLoop is no longer running.
-  // Any tasks scheduled or to be scheduled on the UI MessageLoop will not run.
-  state_ = RUNNING_MANUAL_SHUTDOWN_PUMP;
-
-  // Drain any final tasks manually until the SyncerThread tells us it has
-  // totally finished. There should only ever be 0 or 1 tasks Run() here.
-  while (!syncapi_has_shutdown_) {
-    if (pending_work_)
-      pending_work_->Run();  // OnTaskCompleted will set pending_work_ to NULL.
-
-    // Wait for either a new task or SyncerThread termination.
-    syncapi_event_.Wait();
-  }
-
-  state_ = STOPPED;
-}
-
-void BookmarkModelWorker::CallDoWorkAndSignalTask::Run() {
-  if (!visitor_) {
-    // This can happen during tests or cases where there are more than just the
-    // default BookmarkModelWorker in existence and it gets destroyed before
-    // the main UI loop has terminated.  There is no easy way to assert the
-    // loop is running / not running at the moment, so we just provide cancel
-    // semantics here and short-circuit.
-    // TODO(timsteele): Maybe we should have the message loop destruction
-    // observer fire when the loop has ended, just a bit before it
-    // actually gets destroyed.
-    return;
-  }
-  visitor_->DoWork();
-
-  // Sever ties with visitor_ to allow the sanity-checking above that we don't
-  // get run twice.
-  visitor_ = NULL;
-
-  // Notify the BookmarkModelWorker that scheduled us that we have run
-  // successfully.
-  scheduler_->OnTaskCompleted();
-  work_done_->Signal();  // Unblock the syncer thread that scheduled us.
-}
-
-}  // namespace browser_sync