1133064 - TSan: data race with dom/media/MediaDecoderStateMachine.cpp:2172 DecodeMetadata

Status: RESOLVED FIXED

(Core :: Audio/Video: Playback, defect)

Description

[Nathan Froyd [:froydnj]]

Attachment: media-metadata-decode-race.txt

[The stacks here are partially garbage, but I'm posting this in hopes that somebody more knowledgeable about the media innards might be able to see what is going on here.]

[cribbing from decoder's script, hopefully he won't mind]

The attached logfile shows a thread/data race detected by TSan (ThreadSanitizer).

Typically, races reported by TSan are not false positives, but it is possible that the race is benign. Even in this case though, we should try to come up with a fix unless this would cause unacceptable performance issues. Also note that seemingly benign races can possibly be harmful (also depending on the compiler and the architecture) [1].

If the bug cannot be fixed, then this bug should be used to either make a compile-time annotation for blacklisting or add an entry to the runtime blacklist.

[1] http://software.intel.com/en-us/blogs/2013/01/06/benign-data-races-what-could-possibly-go-wrong

Comment 1

[Nathan Froyd [:froydnj]]

bholley asked to be CC'd on dom/media/ bugs...bholley, do you know what might be going on here?

Comment 2

[Bobby Holley (:bholley)]

Would be helpful to have a link to the revision this was taken from so that I can look at line numbers.

Anyway, I'm totally willing to believe that metadata decoding is racey as hell. I'm doing a bunch of refactoring to fix up the threading model in this code, so I'll file a bug to improve the metadata decoding situation.

Comment 3

[JW Wang [:jwwang] [:jw_wang]]

I am also curious about the revision and line numbers. Since most data are protected by the decoder monitor, what else could it race?

Comment 4

[Bobby Holley (:bholley)]

(In reply to JW Wang [:jwwang] from comment #3)
> I am also curious about the revision and line numbers. Since most data are
> protected by the decoder monitor, what else could it race?

Bug 1136873 should land today - let's see if it's still there after that.

Comment 5

[Anthony Jones (:ajones, :kentuckyfriedtakahe, :k17e)]

Does this issue still exist?

Comment 6

[Kris Wright :KrisWright]

This is a stack for something that appears to be removed. I assume this fixed since it doesn't exist anymore.