Populate .current when navigator.serviceWorker is accessed

content/child/service_worker/service_worker_provider_context.cc

+// Copyright 2014 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/child/service_worker/service_worker_provider_context.h"
+
+#include "base/bind.h"
+#include "base/message_loop/message_loop_proxy.h"
+#include "base/stl_util.h"
+#include "content/child/child_thread.h"
+#include "content/child/service_worker/scoped_service_worker_reference.h"
+#include "content/child/service_worker/service_worker_dispatcher.h"
+#include "content/child/thread_safe_sender.h"
+#include "content/child/worker_task_runner.h"
+#include "content/common/service_worker/service_worker_messages.h"
+
+namespace content {
+
+namespace {
+
+void ForwardMessage(scoped_ptr<IPC::Message> message) {
+  if (ServiceWorkerDispatcher* dispatcher =
+          ServiceWorkerDispatcher::GetThreadSpecificInstance()) {
+    dispatcher->OnMessageReceived(*message);
+  }
+}
+
+}  // namespace
+
+ServiceWorkerProviderContext::ServiceWorkerProviderContext(int provider_id)
+    : provider_id_(provider_id),
+      main_thread_loop_proxy_(base::MessageLoopProxy::current()),
+      thread_safe_sender_(ChildThread::current()->thread_safe_sender()) {
+  ServiceWorkerDispatcher* dispatcher =
+      ServiceWorkerDispatcher::GetOrCreateThreadSpecificInstance(
+          thread_safe_sender_);
+  DCHECK(dispatcher);
+  dispatcher->AddProviderContext(this);
+}
+
+ServiceWorkerProviderContext::~ServiceWorkerProviderContext() {
+  DCHECK(main_thread_loop_proxy_->RunsTasksOnCurrentThread());
+  if (ServiceWorkerDispatcher* dispatcher =
+          ServiceWorkerDispatcher::GetThreadSpecificInstance()) {
+    dispatcher->RemoveProviderContext(this);
+  }
+}
+
+void ServiceWorkerProviderContext::AddProviderThreadAndGetInitializationInfo(
+    int thread_id,
+    scoped_ptr<ScopedServiceWorkerReference>* current) {
+  base::AutoLock lock(lock_);
+  DCHECK(!ContainsKey(provider_thread_ids_, thread_id));
+  provider_thread_ids_.insert(thread_id);
+  if (current_) {
+    *current = ScopedServiceWorkerReference::Create(
+        current_->info(), thread_safe_sender_);
+  }
+}
+
+void ServiceWorkerProviderContext::RemoveProviderThread(int thread_id) {
+  base::AutoLock lock(lock_);
+  provider_thread_ids_.erase(thread_id);
+}
+
+void ServiceWorkerProviderContext::OnServiceWorkerStateChanged(
+    int thread_id,
+    int handle_id,
+    blink::WebServiceWorkerState state) {
+  // Currently .current is the only ServiceWorker associated to this provider.
+  DCHECK_EQ(current_->handle_id(), handle_id);
+  std::set<int> thread_ids;
+  {
+    base::AutoLock lock(lock_);
+    current_->set_state(state);
+    thread_ids = provider_thread_ids_;
+  }
+  ForwardMessageToProviderThreads(
+      ServiceWorkerMsg_ServiceWorkerStateChanged(
+          thread_id, handle_id, state), thread_ids);
+}
+
+void ServiceWorkerProviderContext::OnSetCurrentServiceWorker(
+    int thread_id,
+    int provider_id,
+    const ServiceWorkerObjectInfo& info) {
+  DCHECK_EQ(provider_id_, provider_id);
+  std::set<int> thread_ids;
+  {
+    base::AutoLock lock(lock_);
+    current_ = ScopedServiceWorkerReference::Create(
+        info, thread_safe_sender_);
+    thread_ids = provider_thread_ids_;
+  }
+  ForwardMessageToProviderThreads(
+      ServiceWorkerMsg_SetCurrentServiceWorker(
+          thread_id, provider_id, info), thread_ids);

[falken, 2014/05/01 12:19:29]

I'm trying to understand how this works. At first glance it looks circular...
this function posts a task on several threads to call
SWDispatcher::OnSetCurrentServiceWorker which then calls here. How is the circle
broken?

[kinuko, 2014/05/02 10:00:56]

This may not be very obvious, but:
1. ProviderContext's only attached to the document thread's SWDispatcher
2. ForwardMessageToProviderThreads only forward messages to non-document threads

(Added comments about this)

+}
+
+const ServiceWorkerObjectInfo& ServiceWorkerProviderContext::current() const {
+  base::AutoLock lock(lock_);
+  return current_->info();

[michaeln, 2014/05/01 01:25:18]

don't think we can return this ptr type to the struct here, i'm assuming the
values in info can mutate and it's accessors don't provide thread safetyness

[kinuko, 2014/05/02 10:00:56]

Changed to return it as a value type.

+}
+
+void ServiceWorkerProviderContext::DestructOnMainThread() const {
+  if (!main_thread_loop_proxy_->RunsTasksOnCurrentThread() &&
+      main_thread_loop_proxy_->DeleteSoon(FROM_HERE, this)) {

[michaeln, 2014/05/01 01:25:18]

not sure if its possible for a background thread to be running past the time
where DeleteSoon would return false? might want to leak if the dtor really can't
be run on the main thread instead of running it on the wrong thread

[kinuko, 2014/05/02 10:00:56]

Hmm.. it might be better. Done.

+    return;
+  }
+  delete this;
+}
+
+void ServiceWorkerProviderContext::ForwardMessageToProviderThreads(

[michaeln, 2014/05/01 01:25:18]

I see how messages are forwarded, but I don't see how WebSWProviderImpls on
dedicated worker threads attach themselves to the right SWProviderContext. Can
you walk me thru that? I see it's via the
AddProviderThreadAndGetInitializationInfo() method, but how does the background
thread get a ref to the right SWProviderContext instance to start with?

[kinuko, 2014/05/02 10:00:56]

WebSWProviderImpls are created on the main thread (and then passed on to the
worker thread if it's for dedicated workers), where we can share the document's
provider context info via NetworkProvider.

+    const IPC::Message& message,
+    const std::set<int>& thread_ids) {
+  for (std::set<int>::iterator it = thread_ids.begin();
+       it != thread_ids.end();
+       ++it) {
+    int thread_id = *it;
+    if (thread_id != WorkerTaskRunner::Instance()->CurrentWorkerId()) {
+      WorkerTaskRunner::Instance()->PostTask(
+          thread_id,
+          base::Bind(&ForwardMessage,
+                     base::Passed(make_scoped_ptr(new IPC::Message(message)))));
+    }
+  }
+}
+
+}  // namespace content