1992225 - ThreadSanitizer: lock-order-inversion (potential deadlock) [@ mozilla::detail::RWLockImpl::readLock] through [@ moz_container_wayland_ensure_surface]

Status: NEW

(Core :: Widget: Gtk, defect)

Description

[Jesse Schwartzentruber (:truber)]

The attached crash information was detected on launch with ThreadSanitizer on mozilla-central revision 23edf8f1fbd0.

This appears to be a potential deadlock with wayland startup, but I am only able to reproduce it on my Debian 13 desktop (with Nvidia driver v580.82.09). I wasn't able to reproduce in debian:13 docker using wlheadless-run (it does still repro with wlheadless-run on my desktop). Not sure if this is a false positive.

General information about TSan reports

Why fix races?

Data races are undefined behavior and can cause crashes as well as correctness issues. Compiler optimizations can cause racy code to have unpredictable and hard-to-reproduce behavior.

Rating

If you think this race can cause crashes or correctness issues, it would be great to rate the bug appropriately as P1/P2 and/or indicating this in the bug. This makes it a lot easier for us to assess the actual impact that these reports make and if they are helpful to you.

False Positives / Benign Races

Typically, races reported by TSan are not false positives [1], but it is possible that the race is benign. Even in this case it would be nice to come up with a fix if it is easily doable and does not regress performance. Every race that we cannot fix will have to remain on the suppression list and slows down the overall TSan performance. Also note that seemingly benign races can possibly be harmful (also depending on the compiler, optimizations and the architecture) [2][3].

[1] One major exception is the involvement of uninstrumented code from third-party libraries.
[2] http://software.intel.com/en-us/blogs/2013/01/06/benign-data-races-what-could-possibly-go-wrong
[3] How to miscompile programs with "benign" data races: https://www.usenix.org/legacy/events/hotpar11/tech/final_files/Boehm.pdf

Suppressing unfixable races

If the bug cannot be fixed, then a runtime suppression needs to be added in build/sanitizers/TsanOptions.cpp. The suppressions match on the full stack, so it should be picked such that it is unique to this particular race. The bug number of this bug should also be included so we have some documentation on why this suppression was added.

Comment 1

[Martin Stránský [:stransky] (ni? me)]

Can you add more details? Which race is that?
Thanks.

Comment 2

[Jesse Schwartzentruber (:truber)]

Attachment: log_ffp_asan_1334750.log.1334751.txt

Sorry, I forgot the attachment.

Comment 3

[Jesse Schwartzentruber (:truber)]

This also repros on my Debian/forky laptop with Intel graphics, so it's not Nvidia specific, but could be Debian specific.

Comment 4

[Thinker Li [:sinker]]

I am wandering if this bug relates to the fix of Bug 1979106.

Comment 5

[Martin Stránský [:stransky] (ni? me)]

From the log it looks like M1 and M0 thread are actually the same - it's main thread. Also I don't see any lock there.