Re-land: cc: Implement shared worker contexts.

content/child/child_process.cc

 // Copyright (c) 2012 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/child_process.h"
 
 #if defined(OS_POSIX) && !defined(OS_ANDROID)
 #include <signal.h>  // For SigUSR1Handler below.
 #endif
 
@@ skipping 36 matching lines @@
   base::Thread::Options thread_options(base::MessageLoop::TYPE_IO, 0);
 #if defined(OS_ANDROID)
   thread_options.priority = base::ThreadPriority::DISPLAY;
 #endif
   CHECK(io_thread_.StartWithOptions(thread_options));
 }
 
 ChildProcess::~ChildProcess() {
   DCHECK(g_lazy_tls.Pointer()->Get() == this);
 
+  // Kill the main thread object before nulling child_process, since
+  // destruction code might depend on it.
+  if (main_thread_)  // null in unittests.
+    main_thread_->Shutdown();

[piman, 2015/09/14 21:54:38]

I think you still want to do this after shutdown_event_.Signal(), which is there
to avoid deadlocks (e.g. some thread sending a sync message via a
SyncMessageFilter, and the main thread waiting for that thread to finish).

[reveman, 2015/09/15 20:38:35]

Done. But that meant allowing ChildThreadImpl::AllocateSharedMemory to fail
without a NOTREACHED during shutdown.

+
   // Signal this event before destroying the child process.  That way all
   // background threads can cleanup.
   // For example, in the renderer the RenderThread instances will be able to
   // notice shutdown before the render process begins waiting for them to exit.
   shutdown_event_.Signal();
 
-  // Kill the main thread object before nulling child_process, since
-  // destruction code might depend on it.
-  if (main_thread_) {  // null in unittests.
-    main_thread_->Shutdown();
-    main_thread_.reset();
-  }
-
+  main_thread_.reset();
   g_lazy_tls.Pointer()->Set(NULL);
   io_thread_.Stop();
 }
 
 ChildThreadImpl* ChildProcess::main_thread() {
   return main_thread_.get();
 }
 
 void ChildProcess::set_main_thread(ChildThreadImpl* thread) {
   main_thread_.reset(thread);
@@ skipping 58 matching lines @@
   memset(&sa, 0, sizeof(sa));
   sa.sa_handler = SigUSR1Handler;
   sigaction(SIGUSR1, &sa, NULL);
 
   pause();
 #endif  // defined(OS_ANDROID)
 #endif  // defined(OS_POSIX)
 }
 
 }  // namespace content