1136932 - TSan: data race dom/storage/DOMStorageCache.cpp:322 WaitForPreload

Status: RESOLVED DUPLICATE of bug 1136857

(Core :: DOM: Core & HTML, defect)

Description

[Nathan Froyd [:froydnj]]

Attachment: storage-mloaded-race.txt

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

* Specific information about this bug

Similar to bug 1136926, DOMStorageCache::mLoaded is being read outside of a lock, but modified inside one.  The stack for the write appears to be a bit garbled; the modification I believe it's complaining about is:

http://mxr.mozilla.org/mozilla-central/source/dom/storage/DOMStorageCache.cpp#681

* 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