634825 - crash [@ nsBuiltinDecoderStateMachine::Run()][@ nsBuiltinDecoder::GetPreloadAction ]

Status: VERIFIED FIXED

(Core :: Audio/Video, defect)

Description

[Stuart Parmenter]

This bug was filed from the Socorro interface and is 
report bp-6ab9b81c-6f1a-4891-be44-a9dfd2110216 .
============================================================= 

0 	xul.dll 	nsBuiltinDecoderStateMachine::Run 	content/media/nsBuiltinDecoderStateMachine.cpp:991
1 	xul.dll 	nsThread::ProcessNextEvent 	xpcom/threads/nsThread.cpp:633
2 	xul.dll 	nsThreadStartupEvent::Run 	xpcom/threads/nsThread.cpp:207
3 	nspr4.dll 	_PR_NativeRunThread 	nsprpub/pr/src/threads/combined/pruthr.c:426
4 	nspr4.dll 	pr_root 	nsprpub/pr/src/md/windows/w95thred.c:122
5 	mozcrt19.dll 	_callthreadstartex 	obj-firefox/memory/jemalloc/crtsrc/threadex.c:348
6 	mozcrt19.dll 	__dllonexit 	obj-firefox/memory/jemalloc/crtsrc/onexit.c:276
7 	mozcrt19.dll 	_threadstartex 	obj-firefox/memory/jemalloc/crtsrc/threadex.c:326
8 	ntdll.dll 	ntdll.dll@0x39f01 


I've hit this twice now in today's build when browsing random sites -- not sure steps to reproduce yet.

Comment 1

[Timothy B. Terriberry (:derf)]

+            nsCOMPtr<nsIRunnable> event = new ShutdownThreadEvent(mDecoder->mStateMachineThread);
+            NS_DispatchToMainThread(event, NS_DISPATCH_NORMAL);
+            mDecoder->mStateMachineThread = nsnull;

This part of the patch in bug 631058 interacts badly with nsBuiltinDecoder::Stop():

  if (mStateMachineThread)
    mStateMachineThread->Shutdown();

This is the mechanism used to ensure that the state machine thread is no longer running before the decoder is destroyed. However, by setting mStateMachineThread to nsnull before the ShutdownThreadEvent executes, the check in Stop() will get skipped, even though the state machine thread is still potentially active.

Comment 2

[Scoobidiver (away)]

It is #4 top crasher in today's build.

Comment 3

[Wesley Johnston (:wesj)]

Backed out.

Comment 4

[Johnathan Nightingale [:johnath]]

Would have been a hardblocker, but fixed anyhow.

Comment 5

[u279076]

There have been no recent crash reports with Firefox 4.0b12pre > 20110216.