Unexpected crash in QCoreApplicationPrivate::lockThreadPostEventList

Alexey Volkov

Hi all,
we are facing a strange crash again, backtrace is showing only Qt internals. It happens in the main thread with no clear cause, like in this trace when the system was idle almost half an hour since the last activity.

03.06.2023 04:24:38.860 4 INFO     140645005990208 RSS:  93664
03.06.2023 05:11:12.011 2 CRITICAL 140645005990208 Ooops: signal 11 - Segmentation fault
03.06.2023 05:11:12.011 2 CRITICAL 140645005990208 QThread(0x2589840)
03.06.2023 05:11:12.011 2 CRITICAL 140645005990208
03.06.2023 05:11:12.011 2 CRITICAL 140645005990208 [1] /lib64/libpthread.so.0(+0x13a20) [0x7fea7abd2a20]
03.06.2023 05:11:12.011 2 CRITICAL 140645005990208 [2] /lib64/libQt5Core.so.5(_ZN6QMutex4lockEv+0x15) [0x7fea7ad50845]
03.06.2023 05:11:12.012 2 CRITICAL 140645005990208 [3] /lib64/libQt5Core.so.5(_ZN23QCoreApplicationPrivate23lockThreadPostEventListEP7QObject+0x3d) [0x7fea7af0f8bd]
03.06.2023 05:11:12.012 2 CRITICAL 140645005990208 [4] /lib64/libQt5Core.so.5(_ZN16QCoreApplication9postEventEP7QObjectP6QEventi+0x3d) [0x7fea7af1004d]
03.06.2023 05:11:12.012 2 CRITICAL 140645005990208 [5] /lib64/libQt5Core.so.5(+0x2dd726) [0x7fea7af44726]
03.0
03.06.2023 05:11:12.012 2 CRITICAL 140645005990208 [6] /lib64/libQt5Core.so.5(_ZN7QObject5eventEP6QEvent+0x1bf) [0x7fea7af37edf]
03.06.2023 05:11:12.012 2 CRITICAL 140645005990208 [7] /lib64/libQt5Core.so.5(_ZN16QCoreApplication15notifyInternal2EP7QObjectP6QEvent+0x10b) [0x7fea7af0d7bb]
03.06.2023 05:11:12.012 2 CRITICAL 140645005990208 [8] /lib64/libQt5Core.so.5(_ZN14QTimerInfoList14activateTimersEv+0x423) [0x7fea7af5dea3]
03.06.2023 05:11:12.013 2 CRITICAL 140645005990208 [9] /lib64/libQt5Core.so.5(+0x2f77f4) [0x7fea7af5e7f4]
03.06.2023 05:11:12.013 2 CRITICAL 140645005990208 [10] /lib64/libglib-2.0.so.0(g_main_context_dispatch+0x19f) [0x7fea79d304cf]
03.06.2023 05:11:12.013 2 CRITICAL 140645005990208 [11] /lib64/libglib-2.0.so.0(+0xa94f8) [0x7fea79d844f8]
03.06.2023 05:11:12.013 2 CRITICAL 140645005990208 [12] /lib64/libglib-2.0.so.0(g_main_context_iteration+0x33) [0x7fea79d2dc03]
03.06.2023 05:11:12.013 2 CRITICAL 140645005990208 [13] /lib64/libQt5Core.so.5(_ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE+0x68) [0x7fea7af5ebb8]
03.06.2023 05:11:12.013 2 CRITICAL 140645005990208 [14] /lib64/libQt5Core.so.5(_ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE+0x132) [0x7fea7af0c1e2]
03.06.2023 05:11:12.013 2 CRITICAL 140645005990208 [15] /lib64/libQt5Core.so.5(_ZN16QCoreApplication4execEv+0x94) [0x7fea7af14724]
03.06.2023 05:11:12.013 2 CRITICAL 140645005990208 [16] /srv/bin/omd-server(main+0xa42) [0x4663b2]
03.06.2023 05:11:12.013 2 CRITICAL 140645005990208 [17] /lib64/libc.so.6(__libc_start_main+0xd5) [0x7fea7a697b75]
03.06.2023 05:11:12.013 2 CRITICAL 140645005990208 [18] /srv/bin/omd-server(_start+0x2e) [0x46683e]
03.06.2023 05:11:12.013 2 CRITICAL 140645005990208
0

Qt version is 5.15.2, but I tried also with 5.15.9 static build, same trace except the entries from the single exe module.

I know that it is almost unreal to guess without the reproducible example, but maybe someone has a suggestion of what is this call sequence doing when it tries to lock a released mutex, so I could inspect the potential misuse on my side?

Thanks a lot!