web-threads: Create a single instance of WebThread for each blink thread.

content/child/blink_platform_impl.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/blink_platform_impl.h"
 
 #include <math.h>
 
 #include <vector>
 
 #include "base/allocator/allocator_extension.h"
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/singleton.h"
-#include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/process/process_metrics.h"
 #include "base/rand_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/synchronization/lock.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/sys_info.h"
@@ skipping 384 matching lines @@
   }
   return -1;
 }
 
 BlinkPlatformImpl::BlinkPlatformImpl()
     : main_thread_task_runner_(base::MessageLoopProxy::current()),
       shared_timer_func_(NULL),
       shared_timer_fire_time_(0.0),
       shared_timer_fire_time_was_set_while_suspended_(false),
       shared_timer_suspended_(0),
-      current_thread_slot_(&DestroyCurrentThread) {
+      current_thread_slot_() {
   InternalInit();
 }
 
 BlinkPlatformImpl::BlinkPlatformImpl(
     scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner)
     : main_thread_task_runner_(main_thread_task_runner),
       shared_timer_func_(NULL),
       shared_timer_fire_time_(0.0),
       shared_timer_fire_time_was_set_while_suspended_(false),
       shared_timer_suspended_(0),
-      current_thread_slot_(&DestroyCurrentThread) {
+      current_thread_slot_() {
   // TODO(alexclarke): Use c++11 delegated constructors when allowed.
   InternalInit();
 }
 
 void BlinkPlatformImpl::InternalInit() {
   // ChildThread may not exist in some tests.
   if (ChildThreadImpl::current()) {
     geofencing_provider_.reset(new WebGeofencingProviderImpl(
         ChildThreadImpl::current()->thread_safe_sender()));
     bluetooth_.reset(
         new WebBluetoothImpl(ChildThreadImpl::current()->thread_safe_sender()));
     thread_safe_sender_ = ChildThreadImpl::current()->thread_safe_sender();
     notification_dispatcher_ =
         ChildThreadImpl::current()->notification_dispatcher();
     push_dispatcher_ = ChildThreadImpl::current()->push_dispatcher();
   }
 
   if (main_thread_task_runner_.get()) {
     shared_timer_.SetTaskRunner(main_thread_task_runner_);
   }
 }
 
+void BlinkPlatformImpl::UpdateWebThreadTLS(blink::WebThread* thread) {
+  DCHECK(!current_thread_slot_.Get());
+  current_thread_slot_.Set(thread);
+}
+
 BlinkPlatformImpl::~BlinkPlatformImpl() {
 }
 
 WebURLLoader* BlinkPlatformImpl::createURLLoader() {
   ChildThreadImpl* child_thread = ChildThreadImpl::current();
   // There may be no child thread in RenderViewTests.  These tests can still use
   // data URLs to bypass the ResourceDispatcher.
   return new WebURLLoaderImpl(
       child_thread ? child_thread->resource_dispatcher() : NULL,
       MainTaskRunnerForCurrentThread());
@@ skipping 27 matching lines @@
 
 bool BlinkPlatformImpl::isReservedIPAddress(
     const blink::WebString& host) const {
   net::IPAddressNumber address;
   if (!net::ParseURLHostnameToNumber(host.utf8(), &address))
     return false;
   return net::IsIPAddressReserved(address);
 }
 
 blink::WebThread* BlinkPlatformImpl::createThread(const char* name) {
-  return new WebThreadImpl(name);
+  WebThreadImpl* thread = new WebThreadImpl(name);
+  thread->TaskRunner()->PostTask(
+      FROM_HERE, base::Bind(&BlinkPlatformImpl::UpdateWebThreadTLS,
+                            base::Unretained(this), thread));
+  return thread;
 }
 
 blink::WebThread* BlinkPlatformImpl::currentThread() {
-  WebThreadImplForMessageLoop* thread =
-      static_cast<WebThreadImplForMessageLoop*>(current_thread_slot_.Get());
-  if (thread)
-    return (thread);
-
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner =
-      MainTaskRunnerForCurrentThread();
-  if (!task_runner.get())
-    return NULL;
-
-  thread = new WebThreadImplForMessageLoop(task_runner);
-  current_thread_slot_.Set(thread);
-  return thread;
+  return static_cast<blink::WebThread*>(current_thread_slot_.Get());

[kinuko, 2015/02/27 09:54:27]

Hmm. By looking into the callsites in production code it doesn't look it's super
important to return a meaningful thread value here..

[sadrul, 2015/03/01 10:21:38]

it looks like it's used in some places to add task-observers to the thread (e.g.
MemoryCache, WebDevToolsAgentImpl). Do you think those are always called on the
main-thread?

[kinuko, 2015/03/02 06:08:17]

They belong to main thread afaik. (I'm ok to keep this one for now btw)

[sadrul, 2015/03/02 07:43:14]

If this is only called on the main thread, then indeed we can git rid of the TLS
from here (in fact, it may even be possible to not have
Platform::currentThread(), but I am not sure). I would like to look into that
separately though if that makes sense.

[kinuko, 2015/03/03 00:14:14]

This is not really true, it's also called on the worker thread (but only to
check if it's in unit tests or not) please see this comment:
https://codereview.chromium.org/959803003/#msg11

 }
 
 void BlinkPlatformImpl::yieldCurrentThread() {
   base::PlatformThread::YieldCurrentThread();
 }
 
 blink::WebWaitableEvent* BlinkPlatformImpl::createWaitableEvent() {
   return new WebWaitableEventImpl();
 }
 
@@ skipping 722 matching lines @@
 scoped_refptr<base::SingleThreadTaskRunner>
 BlinkPlatformImpl::MainTaskRunnerForCurrentThread() {
   if (main_thread_task_runner_.get() &&
       main_thread_task_runner_->BelongsToCurrentThread()) {
     return main_thread_task_runner_;
   } else {
     return base::MessageLoopProxy::current();
   }
 }
 
-// static
-void BlinkPlatformImpl::DestroyCurrentThread(void* thread) {
-  WebThreadImplForMessageLoop* impl =
-      static_cast<WebThreadImplForMessageLoop*>(thread);
-  delete impl;
-}
-
 WebString BlinkPlatformImpl::domCodeStringFromEnum(int dom_code) {
   return WebString::fromUTF8(ui::KeycodeConverter::DomCodeToCodeString(
       static_cast<ui::DomCode>(dom_code)));
 }
 
 int BlinkPlatformImpl::domEnumFromCodeString(const WebString& code) {
   return static_cast<int>(ui::KeycodeConverter::CodeStringToDomCode(
       code.utf8().data()));
 }
 
 }  // namespace content