sync: Gracefully handle very early shutdown

chrome/browser/sync/glue/sync_backend_host.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/sync_backend_host.h"
 
 #include <algorithm>
 #include <map>
 
 #include "base/bind.h"
@@ skipping 180 matching lines @@
   // This includes refreshing encryption, setting up the device info change
   // processor, etc.
   void DoInitialProcessControlTypes();
 
   // Some parts of DoInitialProcessControlTypes() may be executed on a different
   // thread.  This function asynchronously continues the work started in
   // DoInitialProcessControlTypes() once that other thread gets back to us.
   void DoFinishInitialProcessControlTypes();
 
   // The shutdown order is a bit complicated:
-  // 1) Call DoStopSyncManagerForShutdown() from |frontend_loop_| to request
-  //    sync manager to stop as soon as possible.
+  // 1) Call the SyncManagerStopHandle's RequestStop() from |frontend_loop_| to
+  //    request sync manager to stop as soon as possible.
   // 2) Post DoShutdown() to sync loop to clean up backend state, save
   //    directory and destroy sync manager.
-  void DoStopSyncManagerForShutdown();
-  void DoShutdown(bool sync_disabled);
+  void DoShutdown(bool sync_disabled,
+                  scoped_ptr<syncer::CancelationSignal> signal);
   void DoDestroySyncManager();
 
   // Configuration methods that must execute on sync loop.
   void DoConfigureSyncer(
       syncer::ConfigureReason reason,
       const DoConfigureSyncerTypes& config_types,
       const syncer::ModelSafeRoutingInfo routing_info,
       const base::Callback<void(syncer::ModelTypeSet,
                                 syncer::ModelTypeSet)>& ready_task,
       const base::Closure& retry_callback);
@@ skipping 81 matching lines @@
       profile_(profile),
       name_(name),
       core_(new Core(name_, profile_->GetPath().Append(kSyncDataFolderName),
                      weak_ptr_factory_.GetWeakPtr())),
       initialization_state_(NOT_ATTEMPTED),
       sync_prefs_(sync_prefs),
       frontend_(NULL),
       cached_passphrase_type_(syncer::IMPLICIT_PASSPHRASE),
       invalidator_(
           invalidation::InvalidationServiceFactory::GetForProfile(profile)),
-      invalidation_handler_registered_(false) {
+      invalidation_handler_registered_(false),
+      cancelation_signal_(new syncer::CancelationSignal()) {
 }
 
 SyncBackendHost::SyncBackendHost(Profile* profile)
     : weak_ptr_factory_(this),
       frontend_loop_(base::MessageLoop::current()),
       profile_(profile),
       name_("Unknown"),
       initialization_state_(NOT_ATTEMPTED),
       frontend_(NULL),
       cached_passphrase_type_(syncer::IMPLICIT_PASSPHRASE),
@@ skipping 75 matching lines @@
       credentials,
       invalidator_->GetInvalidatorClientId(),
       sync_manager_factory.Pass(),
       delete_sync_data_folder,
       sync_prefs_->GetEncryptionBootstrapToken(),
       sync_prefs_->GetKeystoreEncryptionBootstrapToken(),
       scoped_ptr<InternalComponentsFactory>(
           new InternalComponentsFactoryImpl(factory_switches)).Pass(),
       unrecoverable_error_handler.Pass(),
       report_unrecoverable_error_function,
-      !cl->HasSwitch(switches::kSyncDisableOAuth2Token)));
+      !cl->HasSwitch(switches::kSyncDisableOAuth2Token),
+      cancelation_signal_.get()));
   InitCore(init_opts.Pass());
 }
 
 void SyncBackendHost::UpdateCredentials(const SyncCredentials& credentials) {
   DCHECK(registrar_->sync_thread()->IsRunning());
   registrar_->sync_thread()->message_loop()->PostTask(FROM_HERE,
       base::Bind(&SyncBackendHost::Core::DoUpdateCredentials,
                  core_.get(),
                  credentials));
 }
@@ skipping 70 matching lines @@
   // clicks OK, immediately reopens the advanced settings dialog, and gets an
   // unnecessary prompt for a passphrase.
   // Note: It is not guaranteed that the passphrase will be accepted by the
   // syncer thread, since we could receive a new nigori node while the task is
   // pending. This scenario is a valid race, and SetDecryptionPassphrase can
   // trigger a new OnPassphraseRequired if it needs to.
   NotifyPassphraseAccepted();
   return true;
 }
 
-void SyncBackendHost::StopSyncManagerForShutdown() {
-  DCHECK_GT(initialization_state_, NOT_ATTEMPTED);
-  if (initialization_state_ == CREATING_SYNC_MANAGER) {
-    // We post here to implicitly wait for the SyncManager to be created,
-    // if needed.  We have to wait, since we need to shutdown immediately,
-    // and we need to tell the SyncManager so it can abort any activity
-    // (net I/O, data application).
-    DCHECK(registrar_->sync_thread()->IsRunning());
-    registrar_->sync_thread()->message_loop()->PostTask(FROM_HERE,
-        base::Bind(&SyncBackendHost::Core::DoStopSyncManagerForShutdown,
-                   core_.get()));
-  } else {
-    core_->DoStopSyncManagerForShutdown();
-  }
-}
-
 void SyncBackendHost::StopSyncingForShutdown() {
   DCHECK_EQ(base::MessageLoop::current(), frontend_loop_);
+  DCHECK_GT(initialization_state_, NOT_ATTEMPTED);
 
   // Immediately stop sending messages to the frontend.
   frontend_ = NULL;
 
   // Stop listening for and forwarding locally-triggered sync refresh requests.
   notification_registrar_.RemoveAll();
 
   DCHECK(registrar_->sync_thread()->IsRunning());
 
   registrar_->RequestWorkerStopOnUIThread();
 
-  StopSyncManagerForShutdown();
+  cancelation_signal_->RequestStop();
 }
 
 scoped_ptr<base::Thread> SyncBackendHost::Shutdown(ShutdownOption option) {
   // StopSyncingForShutdown() (which nulls out |frontend_|) should be
   // called first.
   DCHECK(!frontend_);
   DCHECK(registrar_->sync_thread()->IsRunning());
 
   bool sync_disabled = (option == DISABLE_AND_CLAIM_THREAD);
   bool sync_thread_claimed =
       (option == DISABLE_AND_CLAIM_THREAD || option == STOP_AND_CLAIM_THREAD);
 
   if (invalidation_handler_registered_) {
     if (sync_disabled) {
       UnregisterInvalidationIds();
     }
     invalidator_->UnregisterInvalidationHandler(this);
     invalidator_ = NULL;
   }
   invalidation_handler_registered_ = false;
 
   // Shut down and destroy sync manager.
+  //
+  // We're about to drop our reference to the |core_|.  The only thing keeping
+  // it alive will be the reference that lives inside this closure we're about
+  // to post to the sync thread.  If this closure doesn't run right away, it's
+  // possible that our Core will outlive us.
+  //
+  // This is a problem for the |cancelation_signal_|, which must outlive the
+  // SyncManager, SyncScheduler, etc.  It can be destroyed only after the call
+  // to DoDestroySyncManager.  The SyncBackendHost might not live that long, but
+  // this closure will.  We pass ownership of the |cancelation_signal_| to this
+  // closure to keep it alive.
   registrar_->sync_thread()->message_loop()->PostTask(
       FROM_HERE,
       base::Bind(&SyncBackendHost::Core::DoShutdown,
-                 core_.get(), sync_disabled));
+                 core_.get(), sync_disabled,
+                 base::Passed(&cancelation_signal_)));
   core_ = NULL;
 
   // Worker cleanup.
   SyncBackendRegistrar* detached_registrar = registrar_.release();
   detached_registrar->sync_thread()->message_loop()->PostTask(
       FROM_HERE,
       base::Bind(&SyncBackendRegistrar::Shutdown,
                  base::Unretained(detached_registrar)));
 
   js_backend_.Reset();
@@ skipping 315 matching lines @@
     const syncer::SyncCredentials& credentials,
     const std::string& invalidator_client_id,
     scoped_ptr<syncer::SyncManagerFactory> sync_manager_factory,
     bool delete_sync_data_folder,
     const std::string& restored_key_for_bootstrapping,
     const std::string& restored_keystore_key_for_bootstrapping,
     scoped_ptr<InternalComponentsFactory> internal_components_factory,
     scoped_ptr<syncer::UnrecoverableErrorHandler> unrecoverable_error_handler,
     syncer::ReportUnrecoverableErrorFunction
         report_unrecoverable_error_function,
-    bool use_oauth2_token)
+    bool use_oauth2_token,
+    syncer::CancelationSignal* const cancelation_signal)
     : sync_loop(sync_loop),
       registrar(registrar),
       routing_info(routing_info),
       workers(workers),
       extensions_activity(extensions_activity),
       event_handler(event_handler),
       service_url(service_url),
       make_http_bridge_factory_fn(make_http_bridge_factory_fn),
       credentials(credentials),
       invalidator_client_id(invalidator_client_id),
       sync_manager_factory(sync_manager_factory.Pass()),
       delete_sync_data_folder(delete_sync_data_folder),
       restored_key_for_bootstrapping(restored_key_for_bootstrapping),
       restored_keystore_key_for_bootstrapping(
           restored_keystore_key_for_bootstrapping),
       internal_components_factory(internal_components_factory.Pass()),
       unrecoverable_error_handler(unrecoverable_error_handler.Pass()),
       report_unrecoverable_error_function(
           report_unrecoverable_error_function),
-      use_oauth2_token(use_oauth2_token) {
+      use_oauth2_token(use_oauth2_token),
+      cancelation_signal(cancelation_signal) {
 }
 
 SyncBackendHost::DoInitializeOptions::~DoInitializeOptions() {}
 
 SyncBackendHost::Core::Core(const std::string& name,
                             const base::FilePath& sync_data_folder_path,
                             const base::WeakPtr<SyncBackendHost>& backend)
     : name_(name),
       sync_data_folder_path_(sync_data_folder_path),
       host_(backend),
@@ skipping 244 matching lines @@
                       options->extensions_activity,
                       options->registrar /* as SyncManager::ChangeDelegate */,
                       options->credentials,
                       options->invalidator_client_id,
                       options->restored_key_for_bootstrapping,
                       options->restored_keystore_key_for_bootstrapping,
                       options->internal_components_factory.get(),
                       &encryptor_,
                       options->unrecoverable_error_handler.Pass(),
                       options->report_unrecoverable_error_function,
-                      options->use_oauth2_token);
+                      options->use_oauth2_token,
+                      options->cancelation_signal);
 
   // |sync_manager_| may end up being NULL here in tests (in
   // synchronous initialization mode).
   //
   // TODO(akalin): Fix this behavior (see http://crbug.com/140354).
   if (sync_manager_) {
     // Now check the command line to see if we need to simulate an
     // unrecoverable error for testing purpose. Note the error is thrown
     // only if the initialization succeeded. Also it makes sense to use this
     // flag only when restarting the browser with an account already setup. If
@@ skipping 89 matching lines @@
   DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
   sync_manager_->GetEncryptionHandler()->SetDecryptionPassphrase(
       passphrase);
 }
 
 void SyncBackendHost::Core::DoEnableEncryptEverything() {
   DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
   sync_manager_->GetEncryptionHandler()->EnableEncryptEverything();
 }
 
-void SyncBackendHost::Core::DoStopSyncManagerForShutdown() {
-  if (sync_manager_)
-    sync_manager_->StopSyncingForShutdown();
-}
+void SyncBackendHost::Core::DoShutdown(
+    bool sync_disabled,
+    scoped_ptr<syncer::CancelationSignal> signal) {
+  DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
 
-void SyncBackendHost::Core::DoShutdown(bool sync_disabled) {
-  DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
   // It's safe to do this even if the type was never activated.
   registrar_->DeactivateDataType(syncer::DEVICE_INFO);
   synced_device_tracker_.reset();
 
   DoDestroySyncManager();
 
   registrar_ = NULL;
 
   if (sync_disabled)
     DeleteSyncDataFolder();
@@ skipping 307 matching lines @@
 
 base::MessageLoop* SyncBackendHost::GetSyncLoopForTesting() {
   return registrar_->sync_thread()->message_loop();
 }
 
 #undef SDVLOG
 
 #undef SLOG
 
 }  // namespace browser_sync