967465 - TSan: data race js/src/../../js/src/vm/Runtime.h:828 script

Status: RESOLVED DUPLICATE of bug 967462

(Core :: JavaScript Engine, defect)

Description

[Christian Holler (:decoder)]

Attachment: Logfile with TSan trace

The attached logfile shows a thread/data race (mozilla-central revision 44ba69cacd7e) 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 inacceptable 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

[Andrew McCreight [:mccr8]]

This looks related to off-main-thread Ion compilation.

Comment 2

[Jan de Mooij [:jandem]]

This is the same problem as bug 967462, rt->numCompilationThreads.

In this case the main thread decrements it in FinishOffThreadBuilder. The compilation thread uses AutoLockForCompilation and reads numCompilationThreads to decide if it should take the lock.