931144 - TSan: Blacklist JSRuntime::updateMallocCounter

Status: RESOLVED FIXED

(Core :: JavaScript: GC, defect)

Description

[Christian Holler (:decoder)]

The code in JSRuntime::updateMallocCounter does a racy update to gcMallocBytes, but according to the code comments, that is intended/accepted:

>     /* We tolerate any thread races when updating gcMallocBytes. */
>     ptrdiff_t oldCount = gcMallocBytes;
>     ptrdiff_t newCount = oldCount - ptrdiff_t(nbytes);
>     gcMallocBytes = newCount;


Since this function does not do anything else, there is no risk in blacklisting it.

Comment 1

[Christian Holler (:decoder)]

Attachment: updateMallocCounter-blacklist.patch

Comment 2

[Jon Coppeard (:jonco)]

Comment on attachment 822474 [details] [diff] [review]
updateMallocCounter-blacklist.patch

Review of attachment 822474 [details] [diff] [review]:
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I don't mind blacklisting this for now, but a better solution may be to use atomics here.

This function is also touched by bug 926678 which I hope to land soon.

Comment 3

[Kris Wright :KrisWright]

Looks like the malloc counter was replaced in bug 1569564, and the new one doesn't seem to raise any questions with tsan, so unless there's any concerns with the new malloc counter I'm going to close this old bug.