[login_manager] Fix thread-safety issues at shutdown

session_manager_service.cc

 // Copyright (c) 2009-2010 The Chromium OS 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 "login_manager/session_manager_service.h"
 
 #include <dbus/dbus-glib-lowlevel.h>
 #include <errno.h>
 #include <glib.h>
 #include <grp.h>
@@ skipping 310 matching lines @@
   if (session_started_) {
     DLOG(INFO) << "emitting D-Bus signal SessionStateChanged:stopped";
     if (signals_[kSignalSessionStateChanged]) {
       g_signal_emit(session_manager_,
                     signals_[kSignalSessionStateChanged],
                     0, "stopped", current_user_.c_str());
     }
   }
 
   // Even if we haven't gotten around to processing a persist task.
-  store_->Persist();
+  base::WaitableEvent event(true, false);
+  io_thread_.message_loop()->PostTask(
+      FROM_HERE, NewRunnableMethod(this,
+                                   &SessionManagerService::PersistStoreSync,
+                                   &event));
+  event.Wait();
   io_thread_.Stop();
   message_loop_->PostTask(FROM_HERE, new MessageLoop::QuitTask());
   LOG(INFO) << "SessionManagerService quitting run loop";
   return true;
 }
 
 void SessionManagerService::RunChildren() {
   bootstat_log("chrome-exec");
   for (size_t i_child = 0; i_child < child_jobs_.size(); ++i_child) {
     ChildJobInterface* child_job = child_jobs_[i_child];
@@ skipping 560 matching lines @@
 
 void SessionManagerService::PersistWhitelist() {
   LOG(INFO) << "Persisting Whitelist to disk.";
   bool what_happened = store_->Persist();
   message_loop_->PostTask(
       FROM_HERE, NewRunnableMethod(this, &SessionManagerService::SendSignal,
                                    chromium::kWhitelistChangeCompleteSignal,
                                    what_happened));
 }
 
+void SessionManagerService::PersistStoreSync(base::WaitableEvent* event) {
+  store_->Persist();
+  LOG(INFO) << "Persisted Store to disk.";
+  event->Signal();
+}
+
 void SessionManagerService::PersistStore() {
   LOG(INFO) << "Persisting Store to disk.";
   bool what_happened = store_->Persist();
   message_loop_->PostTask(
       FROM_HERE, NewRunnableMethod(this, &SessionManagerService::SendSignal,
                                    chromium::kPropertyChangeCompleteSignal,
                                    what_happened));
 }
 
 // static
@@ skipping 309 matching lines @@
       arg_list.push_back(args[i_arg]);
     }
   }
   if (arg_list.size()) {
     arg_lists.push_back(arg_list);
   }
   return arg_lists;
 }
 
 }  // namespace login_manager