Use BrowserThreadMessageLoopProxy to post messages to

watched browser thread.

Store away thread_id using Debug::Alias so that optimizer doesn't
optimize away the code so that we can see the thread_id that is 
hung from the crash dumps in windbg.

Stop the WatchDog thread before stopping other threads to see if
it fixes the racy condition duriong shutdown.

BUG=83564, 86818, 89141, 83343, 83430
TEST=ThreadWatcher unit tests
R=jar
Review URL: http://codereview.chromium.org/7218030

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@92588 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 12 insertions, 10 deletions

diff --git a/chrome/browser/metrics/thread_watcher.cc b/chrome/browser/metrics/thread_watcher.cc
index 2b0da7e..536402d 100644
--- a/chrome/browser/metrics/thread_watcher.cc
+++ b/chrome/browser/metrics/thread_watcher.cc
@@ -2,13 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "chrome/browser/metrics/thread_watcher.h"
+
 #include <math.h>  // ceil
 
+#include "base/debug/alias.h"
 #include "base/string_tokenizer.h"
 #include "base/threading/thread_restrictions.h"
 #include "build/build_config.h"
 #include "chrome/browser/metrics/metrics_service.h"
-#include "chrome/browser/metrics/thread_watcher.h"
 #include "chrome/common/chrome_switches.h"
 #include "content/common/notification_service.h"
 
@@ -29,6 +31,7 @@ ThreadWatcher::ThreadWatcher(const BrowserThread::ID& thread_id,
                              uint32 live_threads_threshold)
     : thread_id_(thread_id),
       thread_name_(thread_name),
+      watched_loop_(BrowserThread::GetMessageLoopProxyForThread(thread_id)),
       sleep_time_(sleep_time),
       unresponsive_time_(unresponsive_time),
       ping_time_(base::TimeTicks::Now()),
@@ -141,8 +144,7 @@ void ThreadWatcher::PostPingMessage() {
   // Send a ping message to the watched thread.
   Task* callback_task = method_factory_.NewRunnableMethod(
       &ThreadWatcher::OnPongMessage, ping_sequence_number_);
-  if (BrowserThread::PostTask(
-          thread_id(),
+  if (watched_loop_->PostTask(
           FROM_HERE,
           NewRunnableFunction(
               &ThreadWatcher::OnPingMessage, thread_id_, callback_task))) {
@@ -292,10 +294,10 @@ void ThreadWatcher::GotNoResponse() {
 
   // Crash the browser if the watched thread is to be crashed on hang and if the
   // number of other threads responding is equal to live_threads_threshold_.
-  if (crash_on_hang_ && responding_thread_count == live_threads_threshold_) {
-    int* crash = NULL;
-    CHECK(crash + thread_id_);
-  }
+  int thread_id = thread_id_;
+  base::debug::Alias(&thread_id);
+  if (crash_on_hang_ && responding_thread_count == live_threads_threshold_)
+    CHECK(false);
 
   hung_processing_complete_ = true;
 }
@@ -486,9 +488,6 @@ void ThreadWatcherList::StartWatching(
     uint32 live_threads_threshold) {
   DCHECK(WatchDogThread::CurrentlyOnWatchDogThread());
 
-  if (!BrowserThread::IsMessageLoopValid(thread_id))
-    return;
-
   std::set<std::string>::const_iterator it =
       crash_on_hang_thread_names.find(thread_name);
   bool crash_on_hang = (it != crash_on_hang_thread_names.end());
diff --git a/chrome/browser/metrics/thread_watcher.h b/chrome/browser/metrics/thread_watcher.h
index a53316c..a66a837 100644
--- a/chrome/browser/metrics/thread_watcher.h
+++ b/chrome/browser/metrics/thread_watcher.h
@@ -199,6 +199,9 @@ class ThreadWatcher {
   // The name of the thread being watched.
   const std::string thread_name_;
 
+  // Used to post messages to watched thread.
+  scoped_refptr<base::MessageLoopProxy> watched_loop_;
+
   // It is the sleep time between the receipt of a pong message back, and the
   // sending of another ping message.
   const base::TimeDelta sleep_time_;