Fix IndexedDB race condition during shutdown.

chrome/browser/in_process_webkit/webkit_context.cc

 // Copyright (c) 2010 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/in_process_webkit/webkit_context.h"
 
 #include "base/command_line.h"
+#include "base/synchronization/waitable_event.h"
+#include "base/task.h"
 #include "chrome/browser/browser_thread.h"
 #include "chrome/browser/profiles/profile.h"
 
+namespace {
+
+template<typename T>
+class DeletionTask : public Task {
+ public:
+  DeletionTask(T* object, base::WaitableEvent& event)
+      : object_(object),
+        event_(event) {}
+
+  // From Task.
+  virtual void Run() {
+    delete object_;
+    event_.Signal();
+  };
+
+ private:
+  T* object_;
+  base::WaitableEvent& event_;

[jorlow, 2011/01/12 17:08:21]

Why not a pointer?  That seems more typical.

+};
+
+template <typename T>
+void DeleteOnThread(BrowserThread::ID thread_id, T* object) {

[jorlow, 2011/01/12 17:08:21]

This is doing more than deleting on a particular thread.  Maybe the name should
somehow mention that it can block.

+  base::WaitableEvent event(true, false);
+  Task* delete_task = new DeletionTask<T>(object, event);
+
+  if (BrowserThread::PostTask(thread_id, FROM_HERE, delete_task)) {

[jorlow, 2011/01/12 17:08:21]

no {}'s

+    event.Wait();
+  } else {
+    delete object;
+  }
+}
+
+}  // namespace
+
 WebKitContext::WebKitContext(Profile* profile, bool clear_local_state_on_exit)
     : data_path_(profile->IsOffTheRecord() ? FilePath() : profile->GetPath()),
       is_incognito_(profile->IsOffTheRecord()),
       clear_local_state_on_exit_(clear_local_state_on_exit),
       ALLOW_THIS_IN_INITIALIZER_LIST(
           dom_storage_context_(new DOMStorageContext(this))),
       ALLOW_THIS_IN_INITIALIZER_LIST(
           indexed_db_context_(new IndexedDBContext(this))) {
 }
 
 WebKitContext::~WebKitContext() {
   // If the WebKit thread was ever spun up, delete the object there.  The task
   // will just get deleted if the WebKit thread isn't created (which only
   // happens during testing).
   dom_storage_context_->set_clear_local_state_on_exit_(
       clear_local_state_on_exit_);
   DOMStorageContext* dom_storage_context = dom_storage_context_.release();
   if (!BrowserThread::DeleteSoon(
           BrowserThread::WEBKIT, FROM_HERE, dom_storage_context)) {
     // The WebKit thread wasn't created, and the task got deleted without
     // freeing the DOMStorageContext, so delete it manually.
     delete dom_storage_context;
   }
 
   indexed_db_context_->set_clear_local_state_on_exit(
       clear_local_state_on_exit_);
-  IndexedDBContext* indexed_db_context = indexed_db_context_.release();
-  if (!BrowserThread::DeleteSoon(
-          BrowserThread::WEBKIT, FROM_HERE, indexed_db_context)) {
-    delete indexed_db_context;
-  }
+  DeleteOnThread(BrowserThread::WEBKIT, indexed_db_context_.release());

[jorlow, 2011/01/12 17:08:21]

Hm...so we're going to block the io thread on the WebKit?  Is there any way to
avoid this?  Could we at least do the wait later or something?

 }
 
 void WebKitContext::PurgeMemory() {
   if (!BrowserThread::CurrentlyOn(BrowserThread::WEBKIT)) {
     BrowserThread::PostTask(
         BrowserThread::WEBKIT, FROM_HERE,
         NewRunnableMethod(this, &WebKitContext::PurgeMemory));
     return;
   }
 
@@ skipping 23 matching lines @@
     BrowserThread::PostTask(
         BrowserThread::WEBKIT, FROM_HERE,
         NewRunnableMethod(this, &WebKitContext::DeleteSessionStorageNamespace,
                           session_storage_namespace_id));
     return;
   }
 
   dom_storage_context_->DeleteSessionStorageNamespace(
       session_storage_namespace_id);
 }