ServiceWorker: Stop don't send a message before connection established

content/renderer/service_worker/embedded_worker_instance_client_impl.cc

 // Copyright (c) 2016 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/renderer/service_worker/embedded_worker_instance_client_impl.h"
 
 #include <memory>
 
 #include "base/strings/utf_string_conversions.h"
 #include "content/child/scoped_child_process_reference.h"
 #include "content/common/service_worker/embedded_worker_messages.h"
 #include "content/public/common/content_client.h"
 #include "content/renderer/service_worker/embedded_worker_devtools_agent.h"
 #include "content/renderer/service_worker/service_worker_context_client.h"
 #include "third_party/WebKit/public/web/WebEmbeddedWorker.h"
 #include "third_party/WebKit/public/web/WebEmbeddedWorkerStartData.h"
 
 namespace content {
 
 // static
 void EmbeddedWorkerInstanceClientImpl::Create(
     EmbeddedWorkerDispatcher* dispatcher,
     mojo::InterfaceRequest<mojom::EmbeddedWorkerInstanceClient> request) {
   // This won't be leaked because the lifetime will be managed internally.
   new EmbeddedWorkerInstanceClientImpl(dispatcher, std::move(request));
 }
 
 void EmbeddedWorkerInstanceClientImpl::StopWorkerCompleted() {
   DCHECK(embedded_worker_id_);
-  DCHECK(stop_callback_);
+  DCHECK(!stop_callbacks_.empty());
   dispatcher_->UnregisterWorker(embedded_worker_id_.value());
   embedded_worker_id_.reset();
-  stop_callback_.Run();
+  for (auto& callback : stop_callbacks_)

[nhiroki, 2016/12/15 09:53:15]

Generally, it would be preferable to swap a callback list with an empty list
before invoking each callback like [1] because one of the callbacks could mutate
the callback list during the iteration (I think this case is safe though)

[1]
https://chromium.googlesource.com/chromium/src/+/master/content/browser/servi...

[shimazu, 2016/12/19 08:25:12]

Done.

+    callback.Run();

[nhiroki, 2016/12/15 09:53:15]

Do we need to call EmbeddedWorkerRegistry::OnWorkerStopped() multiple times on
the same worker?

[shimazu, 2016/12/19 08:25:12]

No we don't in terms of the chromium IPC, but mojo IPC requires all callbacks
should be called. 

[nhiroki, 2016/12/19 09:21:55]

What happens when EmbeddedWorkerInstance::Start() is called on the browser
process during several mojo-callbacks are invoked here? I'm concerned that 2nd
or subsequent mojo-callbacks could wrongly cancel the start worker attempt.

[shimazu, 2017/01/05 06:02:41]

Sorry for missing the comment. It's an unwelcome situation. I've updated this
patch not to invoke Stop twice.

+  stop_callbacks_.clear();
   TRACE_EVENT0("ServiceWorker",
                "EmbeddedWorkerInstanceClientImpl::StopWorkerCompleted");
-  stop_callback_.Reset();
   wrapper_ = nullptr;
 }
 
 void EmbeddedWorkerInstanceClientImpl::StartWorker(
     const EmbeddedWorkerStartParams& params,
     mojom::ServiceWorkerEventDispatcherRequest dispatcher_request) {
   DCHECK(ChildThreadImpl::current());
   DCHECK(!wrapper_);
+  DCHECK(!embedded_worker_id_);
   TRACE_EVENT0("ServiceWorker",
                "EmbeddedWorkerInstanceClientImpl::StartWorker");
   embedded_worker_id_ = params.embedded_worker_id;
 
   std::unique_ptr<EmbeddedWorkerDispatcher::WorkerWrapper> wrapper =
       dispatcher_->StartWorkerContext(
           params,
           base::MakeUnique<ServiceWorkerContextClient>(
               params.embedded_worker_id, params.service_worker_version_id,
               params.scope, params.script_url,
               params.worker_devtools_agent_route_id,
               std::move(dispatcher_request), std::move(temporal_self_)));
   wrapper_ = wrapper.get();
   dispatcher_->RegisterWorker(params.embedded_worker_id, std::move(wrapper));
 }
 
 void EmbeddedWorkerInstanceClientImpl::StopWorker(
     const StopWorkerCallback& callback) {
   DCHECK(ChildThreadImpl::current());
+  // StopWorker is possible to be called before StartWorker().
+  if (!wrapper_) {
+    callback.Run();
+    return;
+  }
   DCHECK(embedded_worker_id_);
-  // StopWorker is possible to be called twice or before StartWorker().
-  if (stop_callback_ || !wrapper_)
+  // StopWorker is possible to be called twice.
+  if (!stop_callbacks_.empty()) {
+    stop_callbacks_.push_back(std::move(callback));
     return;
+  }
   TRACE_EVENT0("ServiceWorker", "EmbeddedWorkerInstanceClientImpl::StopWorker");
-  stop_callback_ = std::move(callback);
+  stop_callbacks_.push_back(std::move(callback));
   dispatcher_->RecordStopWorkerTimer(embedded_worker_id_.value());
   wrapper_->worker()->terminateWorkerContext();
 }
 
 EmbeddedWorkerInstanceClientImpl::EmbeddedWorkerInstanceClientImpl(
     EmbeddedWorkerDispatcher* dispatcher,
     mojo::InterfaceRequest<mojom::EmbeddedWorkerInstanceClient> request)
     : dispatcher_(dispatcher),
       binding_(this, std::move(request)),
       temporal_self_(std::unique_ptr<EmbeddedWorkerInstanceClientImpl>(this)),
       wrapper_(nullptr) {
   binding_.set_connection_error_handler(base::Bind(
       &EmbeddedWorkerInstanceClientImpl::OnError, base::Unretained(this)));
 }
 
 EmbeddedWorkerInstanceClientImpl::~EmbeddedWorkerInstanceClientImpl() {}
 
 void EmbeddedWorkerInstanceClientImpl::OnError() {
   // Removes myself if it's owned by myself.
   temporal_self_.reset();
 }
 
 }  // namespace content