Bug 1022376: Properly shut down LoadMonitor threads r=jib

content/media/webrtc/LoadManager.cpp

@@ -58,6 +58,7 @@ LoadManager::LoadManager(int aLoadMeasurementInterval,
 
 LoadManager::~LoadManager()
 {
+  LOG(("LoadManager: shutting down LoadMonitor"));
   mLoadMonitor->Shutdown();
 }
 

content/media/webrtc/LoadMonitor.cpp

@@ -149,11 +149,17 @@ private:
 
 void LoadMonitor::Shutdown()
 {
-  MutexAutoLock lock(mLock);
   if (mLoadInfoThread) {
-    mShutdownPending = true;
-    mCondVar.Notify();
+    {
+      MutexAutoLock lock(mLock);
+      LOG(("LoadMonitor: shutting down"));
+      mShutdownPending = true;
+      mCondVar.Notify();
+    }
 
+    // Note: can't just call ->Shutdown() from here; that spins the event
+    // loop here, causing re-entrancy issues if we're invoked from cycle
+    // collection.  Argh.
     mLoadInfoThread = nullptr;
 
     nsRefPtr<LoadMonitorRemoveObserver> remObsRunner = new LoadMonitorRemoveObserver(this);
@@ -516,8 +522,10 @@ class LoadInfoCollectRunner : public nsRunnable
 {
 public:
   LoadInfoCollectRunner(nsRefPtr<LoadMonitor> loadMonitor,
-                        RefPtr<LoadInfo> loadInfo)
-    : mLoadUpdateInterval(loadMonitor->mLoadUpdateInterval),
+                        RefPtr<LoadInfo> loadInfo,
+                        nsIThread *loadInfoThread)
+    : mThread(loadInfoThread),
+      mLoadUpdateInterval(loadMonitor->mLoadUpdateInterval),
       mLoadNoiseCounter(0)
   {
     mLoadMonitor = loadMonitor;
@@ -526,6 +534,19 @@ public:
 
   NS_IMETHOD Run()
   {
+    if (NS_IsMainThread()) {
+      if (mThread) {
+        // Don't leak threads!
+        mThread->Shutdown(); // can't Shutdown from the thread itself, darn
+        // Don't null out mThread!
+        // See bug 999104.  We must hold a ref to the thread across Dispatch()
+        // since the internal mThread ref could be released while processing
+        // the Dispatch(), and Dispatch/PutEvent itself doesn't hold a ref; it
+        // assumes the caller does.
+      }
+      return NS_OK;
+    }
+
     MutexAutoLock lock(mLoadMonitor->mLock);
     while (!mLoadMonitor->mShutdownPending) {
       mLoadInfo->UpdateSystemLoad();
@@ -543,10 +564,13 @@ public:
 
       mLoadMonitor->mCondVar.Wait(PR_MillisecondsToInterval(mLoadUpdateInterval));
     }
+    // ok, we need to exit safely and can't shut ourselves down (DARN)
+    NS_DispatchToMainThread(this);
     return NS_OK;
   }
 
 private:
+  nsCOMPtr<nsIThread> mThread;
   RefPtr<LoadInfo> mLoadInfo;
   nsRefPtr<LoadMonitor> mLoadMonitor;
   int mLoadUpdateInterval;
@@ -605,7 +629,7 @@ LoadMonitor::Init(nsRefPtr<LoadMonitor> &self)
   NS_NewNamedThread("Sys Load Info", getter_AddRefs(mLoadInfoThread));
 
   nsRefPtr<LoadInfoCollectRunner> runner =
-    new LoadInfoCollectRunner(self, load_info);
+    new LoadInfoCollectRunner(self, load_info, mLoadInfoThread);
   mLoadInfoThread->Dispatch(runner, NS_DISPATCH_NORMAL);
 
   return NS_OK;