Bug 1119158 - Retarget OnDataAvailable to a new I/O thread instead of the image decoding thread pool. r=sworkman

image/build/nsImageModule.cpp

@@ -9,8 +9,8 @@
 #include "mozilla/ModuleUtils.h"
 #include "nsMimeTypes.h"
 
+#include "DecodePool.h"
 #include "ImageFactory.h"
-#include "RasterImage.h"
 #include "ShutdownTracker.h"
 #include "SurfaceCache.h"
 
@@ -92,7 +92,7 @@ mozilla::image::InitModule()
 
   mozilla::image::ShutdownTracker::Initialize();
   mozilla::image::ImageFactory::Initialize();
-  mozilla::image::RasterImage::Initialize();
+  mozilla::image::DecodePool::Initialize();
   mozilla::image::SurfaceCache::Initialize();
   imgLoader::GlobalInit();
   sInitialized = true;

image/src/DecodePool.cpp

@@ -12,6 +12,7 @@
 #include "nsCOMPtr.h"
 #include "nsIObserverService.h"
 #include "nsIThreadPool.h"
+#include "nsThreadUtils.h"
 #include "nsXPCOMCIDInternal.h"
 #include "prsystem.h"
 
@@ -127,35 +128,36 @@ private:
 
 #ifdef MOZ_NUWA_PROCESS
 
-class RIDThreadPoolListener MOZ_FINAL : public nsIThreadPoolListener
+class DecodePoolNuwaListener MOZ_FINAL : public nsIThreadPoolListener
 {
 public:
   NS_DECL_THREADSAFE_ISUPPORTS
-  NS_DECL_NSITHREADPOOLLISTENER
-  
-  RIDThreadPoolListener() { }
 
-private:
+  NS_IMETHODIMP OnThreadCreated()
-  ~RIDThreadPoolListener() { }
+  {
-};
-
-NS_IMPL_ISUPPORTS(RIDThreadPoolListener, nsIThreadPoolListener)
-
-NS_IMETHODIMP
-RIDThreadPoolListener::OnThreadCreated()
-{
     if (IsNuwaProcess()) {
-        NuwaMarkCurrentThread(static_cast<void(*)(void*)>(nullptr), nullptr);
+      NuwaMarkCurrentThread(static_cast<void(*)(void*)>(nullptr), nullptr);
     }
     return NS_OK;
-}
+  }
 
-NS_IMETHODIMP
+  NS_IMETHODIMP OnThreadShuttingDown() { return NS_OK; }
-RIDThreadPoolListener::OnThreadShuttingDown()
+
+private:
+  ~DecodePoolNuwaListener() { }
+};
+
+NS_IMPL_ISUPPORTS(DecodePoolNuwaListener, nsIThreadPoolListener)
+
+class RegisterDecodeIOThreadWithNuwaRunnable : public nsRunnable
 {
+public:
+  NS_IMETHOD Run()
+  {
+    NuwaMarkCurrentThread(static_cast<void(*)(void*)>(nullptr), nullptr);
     return NS_OK;
-}
+  }
-
+};
 #endif // MOZ_NUWA_PROCESS
 
 
@@ -167,6 +169,13 @@ RIDThreadPoolListener::OnThreadShuttingDown()
 
 NS_IMPL_ISUPPORTS(DecodePool, nsIObserver)
 
+/* static */ void
+DecodePool::Initialize()
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  DecodePool::Singleton();
+}
+
 /* static */ DecodePool*
 DecodePool::Singleton()
 {
@@ -180,8 +189,9 @@ DecodePool::Singleton()
 }
 
 DecodePool::DecodePool()
-  : mThreadPoolMutex("Thread Pool")
+  : mMutex("image::DecodePool")
 {
+  // Initialize the thread pool.
   mThreadPool = do_CreateInstance(NS_THREADPOOL_CONTRACTID);
   MOZ_RELEASE_ASSERT(mThreadPool,
                      "Should succeed in creating image decoding thread pool");
@@ -200,10 +210,22 @@ DecodePool::DecodePool()
 
 #ifdef MOZ_NUWA_PROCESS
   if (IsNuwaProcess()) {
-    mThreadPool->SetListener(new RIDThreadPoolListener());
+    mThreadPool->SetListener(new DecodePoolNuwaListener());
   }
 #endif
 
+  // Initialize the I/O thread.
+  nsresult rv = NS_NewNamedThread("ImageIO", getter_AddRefs(mIOThread));
+  MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv) && mIOThread,
+                     "Should successfully create image I/O thread");
+
+#ifdef MOZ_NUWA_PROCESS
+  nsCOMPtr<nsIRunnable> worker = new RegisterDecodeIOThreadWithNuwaRunnable();
+  rv = mIOThread->Dispatch(worker, NS_DISPATCH_NORMAL);
+  MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv),
+                     "Should register decode IO thread with Nuwa process");
+#endif
+
   nsCOMPtr<nsIObserverService> obsSvc = services::GetObserverService();
   if (obsSvc) {
     obsSvc->AddObserver(this, "xpcom-shutdown-threads", false);
@@ -221,17 +243,22 @@ DecodePool::Observe(nsISupports*, const char* aTopic, const char16_t*)
   MOZ_ASSERT(strcmp(aTopic, "xpcom-shutdown-threads") == 0, "Unexpected topic");
 
   nsCOMPtr<nsIThreadPool> threadPool;
+  nsCOMPtr<nsIThread> ioThread;
 
   {
-    MutexAutoLock threadPoolLock(mThreadPoolMutex);
+    MutexAutoLock lock(mMutex);
-    threadPool = mThreadPool;
+    threadPool.swap(mThreadPool);
-    mThreadPool = nullptr;
+    ioThread.swap(mIOThread);
   }
 
   if (threadPool) {
     threadPool->Shutdown();
   }
 
+  if (ioThread) {
+    ioThread->Shutdown();
+  }
+
   return NS_OK;
 }
 
@@ -244,7 +271,7 @@ DecodePool::AsyncDecode(Decoder* aDecoder)
 
   // Dispatch to the thread pool if it exists. If it doesn't, we're currently
   // shutting down, so it's OK to just drop the job on the floor.
-  MutexAutoLock threadPoolLock(mThreadPoolMutex);
+  MutexAutoLock threadPoolLock(mMutex);
   if (mThreadPool) {
     mThreadPool->Dispatch(worker, nsIEventTarget::DISPATCH_NORMAL);
   }
@@ -274,11 +301,19 @@ DecodePool::SyncDecodeIfPossible(Decoder* aDecoder)
 already_AddRefed<nsIEventTarget>
 DecodePool::GetEventTarget()
 {
-  MutexAutoLock threadPoolLock(mThreadPoolMutex);
+  MutexAutoLock threadPoolLock(mMutex);
   nsCOMPtr<nsIEventTarget> target = do_QueryInterface(mThreadPool);
   return target.forget();
 }
 
+already_AddRefed<nsIEventTarget>
+DecodePool::GetIOEventTarget()
+{
+  MutexAutoLock threadPoolLock(mMutex);
+  nsCOMPtr<nsIEventTarget> target = do_QueryInterface(mIOThread);
+  return target.forget();
+}
+
 already_AddRefed<nsIRunnable>
 DecodePool::CreateDecodeWorker(Decoder* aDecoder)
 {

image/src/DecodePool.h

@@ -17,6 +17,7 @@
 #include "nsIEventTarget.h"
 #include "nsIObserver.h"
 
+class nsIThread;
 class nsIThreadPool;
 
 namespace mozilla {
@@ -41,6 +42,10 @@ public:
   NS_DECL_THREADSAFE_ISUPPORTS
   NS_DECL_NSIOBSERVER
 
+  /// Initializes the singleton instance. Should be called from the main thread.
+  static void Initialize();
+
+  /// Returns the singleton instance.
   static DecodePool* Singleton();
 
   /// Ask the DecodePool to run @aDecoder asynchronously and return immediately.
@@ -69,6 +74,15 @@ public:
    */
   already_AddRefed<nsIEventTarget> GetEventTarget();
 
+  /**
+   * Returns an event target interface to the DecodePool's I/O thread. Callers
+   * who want to deliver data to workers on the DecodePool can use this event
+   * target.
+   *
+   * @return An nsIEventTarget interface to the thread pool's I/O thread.
+   */
+  already_AddRefed<nsIEventTarget> GetIOEventTarget();
+
   /**
    * Creates a worker which can be used to attempt further decoding using the
    * provided decoder.
@@ -91,11 +105,10 @@ private:
 
   static StaticRefPtr<DecodePool> sSingleton;
 
-  // mThreadPoolMutex protects mThreadPool. For all RasterImages R,
+  // mMutex protects mThreadPool and mIOThread.
-  // R::mDecodingMonitor must be acquired before mThreadPoolMutex
+  Mutex                     mMutex;
-  // if both are acquired; the other order may cause deadlock.
-  Mutex                     mThreadPoolMutex;
   nsCOMPtr<nsIThreadPool>   mThreadPool;
+  nsCOMPtr<nsIThread>       mIOThread;
 };
 
 } // namespace image

image/src/RasterImage.cpp

@@ -297,14 +297,6 @@ RasterImage::~RasterImage()
   SurfaceCache::RemoveImage(ImageKey(this));
 }
 
-/* static */ void
-RasterImage::Initialize()
-{
-  // Create our singletons now, so we don't have to worry about what thread
-  // they're created on.
-  DecodePool::Singleton();
-}
-
 nsresult
 RasterImage::Init(const char* aMimeType,
                   uint32_t aFlags)

image/src/RasterImage.h

@@ -280,8 +280,6 @@ public:
     return spec;
   }
 
-  static void Initialize();
-
 private:
   void DrawWithPreDownscaleIfNeeded(DrawableFrameRef&& aFrameRef,
                                     gfxContext* aContext,

image/src/imgRequest.cpp

@@ -699,10 +699,9 @@ NS_IMETHODIMP imgRequest::OnStartRequest(nsIRequest *aRequest, nsISupports *ctxt
     nsAutoCString mimeType;
     nsresult rv = httpChannel->GetContentType(mimeType);
     if (NS_SUCCEEDED(rv) && !mimeType.EqualsLiteral(IMAGE_SVG_XML)) {
-      // Image object not created until OnDataAvailable, so forward to static
+      // Retarget OnDataAvailable to the DecodePool's IO thread.
-      // DecodePool directly.
       nsCOMPtr<nsIEventTarget> target =
-        DecodePool::Singleton()->GetEventTarget();
+        DecodePool::Singleton()->GetIOEventTarget();
       rv = retargetable->RetargetDeliveryTo(target);
     }
     PR_LOG(GetImgLog(), PR_LOG_WARNING,