Closed Bug 1637707 Opened 4 months ago Closed 4 months ago

ThreadSanitizer: unlock of an unlocked mutex (or by a wrong thread) in glxtest

Categories

(Core :: Graphics, defect)

defect

Tracking

()

RESOLVED FIXED
mozilla78
Tracking Status
firefox78 --- fixed

People

(Reporter: jkratzer, Assigned: jkratzer)

References

(Blocks 2 open bugs)

Details

(Whiteboard: [fuzzblocker])

Attachments

(1 file)

The following crash information was detected while fuzzing with ThreadSanitizer on mozilla-central revision 20200513-256602905ce8. This bug requires Firefox to be run using xvfb.

WARNING: ThreadSanitizer: unlock of an unlocked mutex (or by a wrong thread) (pid=910)
    #0 pthread_mutex_unlock /builds/worker/fetches/llvm-project/llvm/projects/compiler-rt/lib/tsan/../sanitizer_common/sanitizer_common_interceptors.inc:4153:3 (firefox+0x799b6)
    #1 _init <null> (libEGL_mesa.so.0+0x201f2)
    #2 glxtest /builds/worker/checkouts/gecko/toolkit/xre/glxtest.cpp:523:15 (libxul.so+0x6355bad)
    #3 fire_glxtest_process() /builds/worker/checkouts/gecko/toolkit/xre/glxtest.cpp:560:7 (libxul.so+0x6355e62)
    #4 XREMain::XRE_mainInit(bool*) /builds/worker/checkouts/gecko/toolkit/xre/nsAppRunner.cpp:3069:3 (libxul.so+0x634703e)
    #5 XREMain::XRE_main(int, char**, mozilla::BootstrapConfig const&) /builds/worker/checkouts/gecko/toolkit/xre/nsAppRunner.cpp:4726:16 (libxul.so+0x6352147)
    #6 XRE_main(int, char**, mozilla::BootstrapConfig const&) /builds/worker/checkouts/gecko/toolkit/xre/nsAppRunner.cpp:4807:21 (libxul.so+0x6352734)
    #7 mozilla::BootstrapImpl::XRE_main(int, char**, mozilla::BootstrapConfig const&) /builds/worker/checkouts/gecko/toolkit/xre/Bootstrap.cpp:45:12 (libxul.so+0x635b422)
    #8 do_main /builds/worker/checkouts/gecko/browser/app/nsBrowserApp.cpp:217:22 (firefox+0xc805f)
    #9 main /builds/worker/checkouts/gecko/browser/app/nsBrowserApp.cpp:331:16 (firefox+0xc805f)

  Location is heap block of size 21152 at 0x7ba800006000 allocated by main thread:
    #0 calloc /builds/worker/fetches/llvm-project/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc:667:5 (firefox+0x5a110)
    #1 xcb_connect_to_fd <null> (libxcb.so.1+0xb3c0)
    #2 glxtest /builds/worker/checkouts/gecko/toolkit/xre/glxtest.cpp:523:15 (libxul.so+0x6355bad)
    #3 fire_glxtest_process() /builds/worker/checkouts/gecko/toolkit/xre/glxtest.cpp:560:7 (libxul.so+0x6355e62)
    #4 XREMain::XRE_mainInit(bool*) /builds/worker/checkouts/gecko/toolkit/xre/nsAppRunner.cpp:3069:3 (libxul.so+0x634703e)
    #5 XREMain::XRE_main(int, char**, mozilla::BootstrapConfig const&) /builds/worker/checkouts/gecko/toolkit/xre/nsAppRunner.cpp:4726:16 (libxul.so+0x6352147)
    #6 XRE_main(int, char**, mozilla::BootstrapConfig const&) /builds/worker/checkouts/gecko/toolkit/xre/nsAppRunner.cpp:4807:21 (libxul.so+0x6352734)
    #7 mozilla::BootstrapImpl::XRE_main(int, char**, mozilla::BootstrapConfig const&) /builds/worker/checkouts/gecko/toolkit/xre/Bootstrap.cpp:45:12 (libxul.so+0x635b422)
    #8 do_main /builds/worker/checkouts/gecko/browser/app/nsBrowserApp.cpp:217:22 (firefox+0xc805f)
    #9 main /builds/worker/checkouts/gecko/browser/app/nsBrowserApp.cpp:331:16 (firefox+0xc805f)

  Mutex M2156 (0x7ba80000b230) created at:
    #0 pthread_mutex_unlock /builds/worker/fetches/llvm-project/llvm/projects/compiler-rt/lib/tsan/../sanitizer_common/sanitizer_common_interceptors.inc:4153:3 (firefox+0x799b6)
    #1 _init <null> (libEGL_mesa.so.0+0x201f2)
    #2 glxtest /builds/worker/checkouts/gecko/toolkit/xre/glxtest.cpp:523:15 (libxul.so+0x6355bad)
    #3 fire_glxtest_process() /builds/worker/checkouts/gecko/toolkit/xre/glxtest.cpp:560:7 (libxul.so+0x6355e62)
    #4 XREMain::XRE_mainInit(bool*) /builds/worker/checkouts/gecko/toolkit/xre/nsAppRunner.cpp:3069:3 (libxul.so+0x634703e)
    #5 XREMain::XRE_main(int, char**, mozilla::BootstrapConfig const&) /builds/worker/checkouts/gecko/toolkit/xre/nsAppRunner.cpp:4726:16 (libxul.so+0x6352147)
    #6 XRE_main(int, char**, mozilla::BootstrapConfig const&) /builds/worker/checkouts/gecko/toolkit/xre/nsAppRunner.cpp:4807:21 (libxul.so+0x6352734)
    #7 mozilla::BootstrapImpl::XRE_main(int, char**, mozilla::BootstrapConfig const&) /builds/worker/checkouts/gecko/toolkit/xre/Bootstrap.cpp:45:12 (libxul.so+0x635b422)
    #8 do_main /builds/worker/checkouts/gecko/browser/app/nsBrowserApp.cpp:217:22 (firefox+0xc805f)
    #9 main /builds/worker/checkouts/gecko/browser/app/nsBrowserApp.cpp:331:16 (firefox+0xc805f)

SUMMARY: ThreadSanitizer: unlock of an unlocked mutex (or by a wrong thread) (/usr/lib/x86_64-linux-gnu/libEGL_mesa.so.0+0x201f2) in _init

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 mozglue/build/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.

The following suppression avoids this error:
mutex:libEGL_mesa.so

Component: Startup and Profile System → Graphics
Product: Toolkit → Core
Summary: ThreadSanitizer: unlock of an unlocked mutex (or by a wrong thread) → ThreadSanitizer: unlock of an unlocked mutex (or by a wrong thread) in glxtest
Assignee: nobody → jkratzer
Status: NEW → ASSIGNED
Pushed by choller@mozilla.com:
https://hg.mozilla.org/integration/autoland/rev/09976687c44c
Suppress LibEGL_mesa.so required by xvfb. r=decoder
Status: ASSIGNED → RESOLVED
Closed: 4 months ago
Resolution: --- → FIXED
Target Milestone: --- → mozilla78
Blocks: tsan
Blocks: domino
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