1131714 - TSan: data race js/src/gc/Marking.cpp:701 MarkIdInternal

Status: RESOLVED DUPLICATE of bug 1135100

(Core :: JavaScript: GC, defect)

Description

[Nathan Froyd [:froydnj]]

Attachment: 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

[Terrence Cole [:terrence]]

Fallout from CGC. This race is "safe": both threads will write the same output, even if there is a RAW ordering error. We should still fix the race though, maybe by using weak atomic ops. Forwarding to Jon to look at when he gets back from holiday.