From 6b1a2c2b214492b8117c8abd4dcc6a7a3a138da9 Mon Sep 17 00:00:00 2001
From: Randell Jesup <rjesup@jesup.org>
Date: Tue, 23 Aug 2016 12:47:45 -0400
Subject: [PATCH] Bug 1255737: don't wait more than 15 seconds for an
 AudioCallbackDriver to exit r=pehrsons Avoids running into the
 stalled-shutdown killer if the audio driver/OS is stupid

MozReview-Commit-ID: 58SUg2Xt37C
---
 dom/media/MediaStreamGraph.cpp | 48 ++++++++++++++++++++++++++++++++--
 dom/media/MediaStreamGraph.h   |  2 ++
 2 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/dom/media/MediaStreamGraph.cpp b/dom/media/MediaStreamGraph.cpp
index 09ea5f26f4be..784bd016313e 100644
--- a/dom/media/MediaStreamGraph.cpp
+++ b/dom/media/MediaStreamGraph.cpp
@@ -1448,11 +1448,14 @@ MediaStreamGraphImpl::ForceShutDown(ShutdownTicket* aShutdownTicket)
 
 namespace {
 
-class MediaStreamGraphShutDownRunnable : public Runnable {
+class MediaStreamGraphShutDownRunnable : public Runnable
+                                       , public nsITimerCallback {
 public:
   explicit MediaStreamGraphShutDownRunnable(MediaStreamGraphImpl* aGraph)
     : mGraph(aGraph)
   {}
+  NS_DECL_ISUPPORTS_INHERITED
+
   NS_IMETHOD Run() override
   {
     NS_ASSERTION(mGraph->mDetectedNotRunning,
@@ -1471,10 +1474,30 @@ public:
     }
 #endif
 
+    // Avoid waiting forever for a callback driver to shut down
+    // synchronously.  Reports are that some 3rd-party audio drivers
+    // occasionally hang in shutdown (both for us and Chrome).
+    mTimer = do_CreateInstance(NS_TIMER_CONTRACTID);
+    if (!mTimer) {
+      return NS_ERROR_FAILURE;
+    }
+    mTimer->InitWithCallback(this,
+                             MediaStreamGraph::AUDIO_CALLBACK_DRIVER_SHUTDOWN_TIMEOUT,
+                             nsITimer::TYPE_ONE_SHOT);
+
     mGraph->mDriver->Shutdown(); // This will wait until it's shutdown since
                                  // we'll start tearing down the graph after this
 
     // We may be one of several graphs. Drop ticket to eventually unblock shutdown.
+    NS_ASSERTION(mGraph->mForceShutdownTicket,
+                 "AudioCallbackDriver took too long to shut down and we let shutdown"
+                 " continue - freezing and leaking");
+    if (!mGraph->mForceShutdownTicket) {
+      // The timer fired, so we may be deeper in shutdown now.  Block any further
+      // teardown and just leak, for safety.
+      return NS_OK;
+    }
+    mTimer = nullptr;
     mGraph->mForceShutdownTicket = nullptr;
 
     // We can't block past the final LIFECYCLE_WAITING_FOR_STREAM_DESTRUCTION
@@ -1507,10 +1530,30 @@ public:
     }
     return NS_OK;
   }
+
+  NS_IMETHOD Notify(nsITimer* aTimer) override
+  {
+    // Sigh, driver took too long to shut down.  Stop blocking system
+    // shutdown and hope all is well.  Shutdown of this graph will proceed
+    // if the driver eventually comes back.
+    NS_ASSERTION(!(mGraph->mForceShutdownTicket),
+                 "AudioCallbackDriver took too long to shut down - probably hung");
+
+    mGraph->mForceShutdownTicket = nullptr;
+    return NS_OK;
+  }
+
 private:
+  ~MediaStreamGraphShutDownRunnable() {}
+
+  nsCOMPtr<nsITimer> mTimer;
   RefPtr<MediaStreamGraphImpl> mGraph;
 };
 
+NS_IMPL_ISUPPORTS_INHERITED(MediaStreamGraphShutDownRunnable, Runnable, nsITimerCallback)
+
+
+
 class MediaStreamGraphStableStateRunnable : public Runnable {
 public:
   explicit MediaStreamGraphStableStateRunnable(MediaStreamGraphImpl* aGraph,
@@ -3263,7 +3306,8 @@ MediaStreamGraph::GetInstance(MediaStreamGraph::GraphDriverType aGraphDriverRequ
       public:
         Blocker()
         : media::ShutdownBlocker(NS_LITERAL_STRING(
-            "MediaStreamGraph shutdown: blocking on msg thread")) {}
+            "MediaStreamGraph shutdown: blocking on msg thread"))
+        {}
 
         NS_IMETHOD
         BlockShutdown(nsIAsyncShutdownClient* aProfileBeforeChange) override
diff --git a/dom/media/MediaStreamGraph.h b/dom/media/MediaStreamGraph.h
index ac0715cc54a1..71ae5467ddee 100644
--- a/dom/media/MediaStreamGraph.h
+++ b/dom/media/MediaStreamGraph.h
@@ -1252,6 +1252,8 @@ public:
     SYSTEM_THREAD_DRIVER,
     OFFLINE_THREAD_DRIVER
   };
+  static const uint32_t AUDIO_CALLBACK_DRIVER_SHUTDOWN_TIMEOUT = 15*1000;
+  
   // Main thread only
   static MediaStreamGraph* GetInstance(GraphDriverType aGraphDriverRequested,
                                        dom::AudioChannel aChannel);