1652174 - ThreadSanitizer: data race [@ event_base_loop] vs [@ event_set]

Status: RESOLVED FIXED

(Core :: WebRTC: Audio/Video, defect)

Description

[Byron Campen [:bwc]]

Attachment: tsan output

If true, this looks like a flaw down in libevent. However, it may also be because TSan does not grok fences. Saw this when running webrtc mochitests under TSan. Marking security for now, until we can determine whether this is a real flaw or not.

Comment 1

[Christian Holler (:decoder)]

Which tests exactly did you run for this? We already run Mochitests in CI for TSan and I haven't seen this one before.

Comment 2

[Byron Campen [:bwc]]

(In reply to Christian Holler (:decoder) from comment #1)

Which tests exactly did you run for this? We already run Mochitests in CI for TSan and I haven't seen this one before.

This happens on the webrtc mochitests, which are part of the "mda" mochitest suite (which has no TSan jobs right now, see bug 1648192). It also happens in the webrtc web-platform-tests.

Comment 3

[Byron Campen [:bwc]]

Looks like this is due to this flag:

https://searchfox.org/mozilla-central/rev/1b95a0179507a4dc7d4b0c94c2df420dc1a72885/ipc/chromium/src/third_party/libevent/event.c#251

Probably makes sense to suppress, but is kinda difficult because this flag is touched in macros all over the place.

There is a bug open on libevent: https://github.com/libevent/libevent/issues/777

Comment 4

[Byron Campen [:bwc]]

Can you clear the sec flag on this, it looks pretty much benign to me?

Comment 5

[Byron Campen [:bwc]]

Attachment: Bug 1652174: Suppress TSan race error in libevent's event_debug_mode_too_late r?dminor

See https://github.com/libevent/libevent/issues/777

Depends on D83794

Comment 6

[Byron Campen [:bwc]]

So, I'm not sure this manifests in our IPC code. I have only seen this down in webrtc.org, which also uses libevent.

Comment 7

[Byron Campen [:bwc]]

Try looks good.

https://treeherder.mozilla.org/#/jobs?repo=try&revision=80b0d8448258efa636b6e55d0e1b3118cf87ab97

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/daf7d1c828c5
Suppress TSan race error in libevent's event_debug_mode_too_late r=dminor

Comment 9

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/daf7d1c828c5