Bug 887466 - Rearrange SyncDecode so that we never try to finish a size decode with the decode lock held. r=seth

image/src/RasterImage.cpp

@@ -2325,26 +2325,8 @@ RasterImage::RequestDecodeCore(RequestDecodeType aDecodeType)
 nsresult
 RasterImage::SyncDecode()
 {
-  MutexAutoLock imgLock(mDecodingMutex);
-
-  if (mDecodeRequest) {
-    // If the image is waiting for decode work to be notified, go ahead and do that.
-    if (mDecodeRequest->mRequestStatus == DecodeRequest::REQUEST_WORK_DONE) {
-      nsresult rv = FinishedSomeDecoding();
-      CONTAINER_ENSURE_SUCCESS(rv);
-    }
-  }
-
-  nsresult rv;
-
   PROFILER_LABEL_PRINTF("RasterImage", "SyncDecode", "%s", GetURIString().get());;
 
-  // We really have no good way of forcing a synchronous decode if we're being
-  // called in a re-entrant manner (ie, from an event listener fired by a
-  // decoder), because the decoding machinery is already tied up. We thus explicitly
-  // disallow this type of call in the API, and check for it in API methods.
-  NS_ABORT_IF_FALSE(!mInDecoder, "Yikes, forcing sync in reentrant call!");
-
   // If we have a size decoder open, make sure we get the size
   if (mDecoder && mDecoder->IsSizeDecode()) {
     nsresult rv = DecodePool::Singleton()->DecodeUntilSizeAvailable(this);
@@ -2358,6 +2340,24 @@ RasterImage::SyncDecode()
     }
   }
 
+  MutexAutoLock imgLock(mDecodingMutex);
+
+  // We really have no good way of forcing a synchronous decode if we're being
+  // called in a re-entrant manner (ie, from an event listener fired by a
+  // decoder), because the decoding machinery is already tied up. We thus explicitly
+  // disallow this type of call in the API, and check for it in API methods.
+  NS_ABORT_IF_FALSE(!mInDecoder, "Yikes, forcing sync in reentrant call!");
+
+  if (mDecodeRequest) {
+    // If the image is waiting for decode work to be notified, go ahead and do that.
+    if (mDecodeRequest->mRequestStatus == DecodeRequest::REQUEST_WORK_DONE) {
+      nsresult rv = FinishedSomeDecoding();
+      CONTAINER_ENSURE_SUCCESS(rv);
+    }
+  }
+
+  nsresult rv;
+
   // If we're decoded already, or decoding until the size was available
   // finished us as a side-effect, no worries
   if (mDecoded)

image/src/RasterImage.h

@@ -642,9 +642,9 @@ private: // data
   nsRefPtr<Decoder>          mDecoder;
   nsRefPtr<DecodeRequest>    mDecodeRequest;
   uint32_t                   mBytesDecoded;
-  // END LOCKED MEMBER VARIABLES
 
   bool                       mInDecoder;
+  // END LOCKED MEMBER VARIABLES
 
   // Boolean flags (clustered together to conserve space):
   bool                       mHasSize:1;       // Has SetSize() been called?