Check that all shared workers are terminated.

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index dfc936452cbec217cf9dd94545ebc41112090315..cf4fc4454d29557a97e03d9eb38f646407eecf54 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -712,6 +712,20 @@ void RenderProcessHostImpl::RegisterRendererMainThreadFactory(
   g_renderer_main_thread_factory = create;
 }
 
+// static
+// TODO(alokp): Remove after collecting crash data.
+// Temporary checks to verify that all shared workers are terminated.

[horo, 2016/08/09 04:03:24]

Nit: s/shared workers/shared workers and service workers/

|worker_ref_count_| is used for both shared workers and service workers.

So RenderProcessHostImpl::CheckAllWorkersTerminate() is verifying that all
shared workers and service workers are terminated.

[alokp, 2016/08/09 05:07:26]

Thanks for reviewing. I just commented about shared worker because in
BrowserProcessSubThread::IOThreadPreCleanUp, I am only checking shared workers.
Do you suggest a corresponding check for service worker as well?

[horo, 2016/08/09 06:01:26]

I just suggested that you should change the comment of
RenderProcessHostImpl::CheckAllWorkersTerminated().

But...

Could you please explain why you want to check that all shared workers are
terminated for the bug?
This bug 608049 is caused by unclosed AudioOutputStream instance.

I thought that it is because shared workers can open AudioOutputStream.
But AudioContextConstructor is exposed only in window.
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/modules/webaud...
So I think shared workers can't open AudioOutputStream.
And also, service workers can't open AudioOutputStream.

Is my understanding correct?

[alokp, 2016/08/09 06:35:27]

For more context see crbug.com/628192

All audio streams will get closed if RenderProcessHostImpl::Cleanup is called.
In the past I added a few checks here https://codereview.chromium.org/2133813002
and discovered that worker_ref_count_ > 0 is preventing RenderProcessHostImpl(s)
from getting cleaned up. This patch seeks to further understand why
shared/service workers are not getting cleaned up.

I am not familiar with shared/service workers. I would appreciate any help with
diagnosing it further.

[horo, 2016/08/09 09:00:52]

Ah I got it.

I checked ServiceWorkerProcessManager code now.
And I think ServiceWorkerProcessManager::Shutdown() is correctly calling
DecrementWorkerRefCount.

BrowserMainRunnerImpl::Shutdown()
-> BrowserMainLoop::ShutdownThreadsAndCleanUp()
 -> ChromeBrowserMainParts::PostMainMessageLoopRun()
  -> BrowserProcessImpl::StartTearDown()
   -> ProfileManager::~ProfileManager()
    -> ProfileInfo::~ProfileInfo()
     -> ProfileDestroyer::DestroyProfileWhenAppropriate()
      -> Profile::MaybeSendDestroyedNotification()
       -> BrowserContext::NotifyWillBeDestroyed()
        -> BrowserContext::ForEachStoragePartition()
         -> ShutdownServiceWorkerContext()
          -> ServiceWorkerProcessManager::Shutdown()
           -> RenderProcessHostImpl::DecrementWorkerRefCount()

But there may be edge cases that SharedWorkerServiceImpl doesn't correctly call
DecrementWorkerRefCount.

+// It is suspected that shared workers prevent render process hosts
+// from shutting down: crbug.com/608049
+void RenderProcessHostImpl::CheckAllWorkersTerminated() {
+  iterator iter(AllHostsIterator());
+  while (!iter.IsAtEnd()) {
+    RenderProcessHostImpl* host =
+        static_cast<RenderProcessHostImpl*>(iter.GetCurrentValue());
+    CHECK_EQ(0, host->worker_ref_count_);

[falken, 2016/09/02 07:47:45]

This would infinitely loop, no? iter.Advance() should be called.

+  }
+}
+
 RenderProcessHostImpl::~RenderProcessHostImpl() {
 #ifndef NDEBUG
   DCHECK(is_self_deleted_)