1120591 - TSan: data race js/src/jsgc.cpp:1811 updateForRemovedArena

Status: RESOLVED FIXED

(Core :: JavaScript: GC, defect)

Description

[Nathan Froyd [:froydnj]]

Attachment: tsan-js-gc-race.txt

[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]]

Attachment: tsan-js-gc-race2.txt

Same read location, but different write location, for flavor.

Comment 2

[Andrew McCreight [:mccr8]]

This is gcTriggerBytes_ stuff it looks like.

Comment 3

[Jon Coppeard (:jonco)]

We should be able to move the call to updateAfterGC() to avoid this race.

Comment 4

[Jon Coppeard (:jonco)]

Attachment: bug1120591-tsan-gcTriggerBytes

If we do the update before starting background sweeping we will avoid this race.

Comment 5

[Terrence Cole [:terrence]]

Comment on attachment 8550402 [details] [diff] [review]
bug1120591-tsan-gcTriggerBytes

Review of attachment 8550402 [details] [diff] [review]:
-----------------------------------------------------------------

Yup, makes sense.

Comment 6

[Jon Coppeard (:jonco)]

This change provoked an intermittent test failure of the Debugger-debuggees-28.js jit-test in zeal mode 14 that is fixed by bug 1123394.

Comment 7

[Jon Coppeard (:jonco)]

This change also causes the failure in bug 1121944.

Comment 8

[Jon Coppeard (:jonco)]

https://hg.mozilla.org/integration/mozilla-inbound/rev/2c6305279bd6

Comment 9

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/2c6305279bd6