Fix deadlock in VAAPI video decoder error cases.

content/common/gpu/media/vaapi_video_decode_accelerator.cc

Index: content/common/gpu/media/vaapi_video_decode_accelerator.cc
diff --git a/content/common/gpu/media/vaapi_video_decode_accelerator.cc b/content/common/gpu/media/vaapi_video_decode_accelerator.cc
index 45f7f2b8db9f098fc1fbdbca76a80cdc2f9ab864..301e124143ac4a65650fdacc318b44f23891f1a5 100644
--- a/content/common/gpu/media/vaapi_video_decode_accelerator.cc
+++ b/content/common/gpu/media/vaapi_video_decode_accelerator.cc
@@ -22,7 +22,9 @@
   do {                                                              \
     if (!(result)) {                                                \
       DVLOG(1) << log;                                              \
-      NotifyError(error_code);                                      \
+      message_loop_->PostTask(FROM_HERE, base::Bind(                \

[Ami GONE FROM CHROMIUM, 2012/09/18 02:21:28]

This will delay clearing client_ potentially for longer than we want.

IWBN to instead post the Cleanup() call in NotifyError, instead of posting this
here.

[sheu, 2012/09/19 08:21:35]

That would possibly be racy as well.  I imagine the client might call Destroy()
on this upon receiving the error notification, and a posted Cleanup() task
afterwards would Have A Bad Time.

In any case, this is an error case, and we might be ok with not clearing client_
for a while?

[sheu, 2012/09/19 08:58:57]

Oh!  I see what you're doing there.

Posting the cleanup with weak_this_ should do the trick.  Also, as to clearing
client_: as I understand it, the point of clearing client_ptr_factory_ is to
invalidate all the previous callbacks that haven't completed yet, since they've
all been posted with client_.

+          &VaapiVideoDecodeAccelerator::NotifyError,                \
+          weak_this_, error_code));                                 \
       return ret;                                                   \
     }                                                               \
   } while (0)
@@ -36,15 +38,9 @@ VaapiVideoDecodeAccelerator::InputBuffer::~InputBuffer() {
 }
 
 void VaapiVideoDecodeAccelerator::NotifyError(Error error) {
-  if (message_loop_ != MessageLoop::current()) {
-    DCHECK_EQ(decoder_thread_.message_loop(), MessageLoop::current());
-    message_loop_->PostTask(FROM_HERE, base::Bind(
-        &VaapiVideoDecodeAccelerator::NotifyError, weak_this_, error));
-    return;
-  }
-
+  // Always call this from a posted task, as it calls Cleanup(), which acquires
+  // the member lock_.
   DVLOG(1) << "Notifying of error " << error;
-
   if (client_) {
     client_->NotifyError(error);
     client_ptr_factory_.InvalidateWeakPtrs();