967474 - TSan: data race js/src/../../js/src/jsinfer.h:510 baseFlags

Status: RESOLVED FIXED

(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

[Jan de Mooij [:jandem]]

Attachment: Patch

The problem here is that JSScript::makeTypes is allocating/initializing a TypeScript, and in the meantime that TypeScript is accessible to the background thread (script->types) in IonBuilder::testNeedsArgumentCheck.

This patch initializes TypeScript first, then assigns it.

Comment 3

[Jan de Mooij [:jandem]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/619ffda7b3fe

Comment 4

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/619ffda7b3fe