1136844 - TSan: data race image/src/imgRequest.cpp:150 GetProgressTracker

Status: RESOLVED FIXED

(Core :: Graphics: ImageLib, defect)

Description

[Nathan Froyd [:froydnj]]

Attachment: imgrequest-race.txt

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

* Specific information about this bug

The stacks are a little weird here, but I think it's complaining that we're allocating an Image* in ImageFactory, which initializes mProgressTracker, and then (through inlining etc.), we're accessing that mProgressTracker field in imgRequest::GetProgressTracker.

I initially thought that the race was on imgRequest::mImage, but I don't think that's correct, given that the writing stack says the write is coming from malloc.

Happy to hear alternative interpretations.

* General information about TSan, data races, etc.

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][2].

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
[2] _How to miscompile programs with "benign" data races_: https://www.usenix.org/legacy/events/hotpar11/tech/final_files/Boehm.pdf

Comment 1

[Seth Fowler [:seth] [:s2h]]

Fixed in bug 1137002.