IndexedDB: Prevent store/index deletion from racing ahead of use

content/browser/indexed_db/indexed_db_transaction.cc

 // Copyright (c) 2013 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 "content/browser/indexed_db/indexed_db_transaction.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 68 matching lines @@
 IndexedDBTransaction::~IndexedDBTransaction() {
   // It shouldn't be possible for this object to get deleted until it's either
   // complete or aborted.
   DCHECK_EQ(state_, FINISHED);
   DCHECK(preemptive_task_queue_.empty());
   DCHECK_EQ(pending_preemptive_events_, 0);
   DCHECK(task_queue_.empty());
   DCHECK(abort_task_stack_.empty());
 }
 
-void IndexedDBTransaction::ScheduleTask(Operation task, Operation abort_task) {
-  if (state_ == FINISHED)
-    return;
-
-  timeout_timer_.Stop();
-  used_ = true;
-  task_queue_.push(task);
-  ++diagnostics_.tasks_scheduled;
-  abort_task_stack_.push(abort_task);
-  RunTasksIfStarted();
-}
-
 void IndexedDBTransaction::ScheduleTask(IndexedDBDatabase::TaskType type,
                                         Operation task) {
   if (state_ == FINISHED)
     return;
 
   timeout_timer_.Stop();
   used_ = true;
   if (type == IndexedDBDatabase::NORMAL_TASK) {
     task_queue_.push(task);
     ++diagnostics_.tasks_scheduled;
   } else {
     preemptive_task_queue_.push(task);
   }
   RunTasksIfStarted();

[cmumford, 2014/05/13 21:56:24]

Will PostTask (run by RunTasksIfStarted) ever run the task right away - or will
it always post it to the queue? If so then might we have a case where code calls
ScheduleTask followed by ScheduleAbortTask and the abort isn't run?

[ericu, 2014/05/14 01:08:00]

No, PostTask always queues a task for asynchronous execution; it never runs the
task directly.

 }
 
+void IndexedDBTransaction::ScheduleAbortTask(Operation abort_task) {
+  DCHECK_NE(FINISHED, state_);
+  DCHECK(used_);
+  abort_task_stack_.push(abort_task);
+}
+
 void IndexedDBTransaction::RunTasksIfStarted() {
   DCHECK(used_);
 
   // Not started by the coordinator yet.
   if (state_ != STARTED)
     return;
 
   // A task is already posted.
   if (should_process_queue_)
     return;
@@ skipping 211 matching lines @@
 
 void IndexedDBTransaction::CloseOpenCursors() {
   for (std::set<IndexedDBCursor*>::iterator i = open_cursors_.begin();
        i != open_cursors_.end();
        ++i)
     (*i)->Close();
   open_cursors_.clear();
 }
 
 }  // namespace content