QXcbEventReader segfaults

[Rudolf Leitgeb]

On system startup (Kubuntu 15.04, fully updated) I find the following line in both dmesg and in /var/log/syslog:

kernel: [ 216.806390] QXcbEventReader[1704]: segfault at 7f9cfce12099 ip 00007f9cfce12099 sp 00007f9cef149e60 error 14

File .xsession-errors is unaware of any issue related to this crash, so this crash may start very early in the boot process. Sadly, no application name.

[CassieMoondust (cassie-lx)]

traps: QXcbEventReader[1546] general protection ip:7f9b24aa01cb sp:7f9b17e04bf0 error:0 in libc-2.21.so[7f9b24a21000+1c0000]

Kubuntu 15.10 64-Bit

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Woods Wannamaker (oodsway)]

I also observe errors on boot.

[ 47.551598] QXcbEventReader[1776]: segfault at 7f15a7a5ca39 ip 00007f15a7a5ca39 sp 00007f15a4cc2de0 error 14 in locale-arc
hive[7f15a7aea000+2c9000]

Kubuntu 15.10 64-bit
via upgrade from 15.04
via upgrade from 14.10

[Spadge Fromley (sfromley)]

I too am seeing the error message.

The last two lines in my dmesg on startup:

[ 25.178543] do_general_protection: 24 callbacks suppressed
[ 25.178546] traps: QXcbEventReader[1320] general protection ip:7f2fa247c1cb sp:7f2f98a29bf0 error:0 in libc-2.21.so[7f2fa23fd000+1c0000]

spadge@Venus:~$ uname -a
Linux Venus 4.2.0-18-generic #22-Ubuntu SMP Fri Nov 6 18:25:50 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

Kubuntu 15.10 64-bit

Using:
KDE Frameworks 5.15.0
Qt 5.4.2 (built against 5.4.2)
The xcb windowing system

[Bug Reporter 11 (bugreporter11)]

Kubuntu 15.10 amd64, fully updated.

[ 44.554634] QXcbEventReader[1520]: segfault at 7f30103eaa39 ip 00007f30103eaa39 sp 00007f300de9bde0 error 14 in locale-archive[7f3010478000+2c9000]

Linux kbox-2016 4.2.0-25-generic #30-Ubuntu SMP Mon Jan 18 12:31:50 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

[max63 (maxime-chassagneux)]

same problem for me :

[ 14.997370] QXcbEventReader[1731]: segfault at 7f184d2b6a39 ip 00007f184d2b6a39 sp 00007f184a51cde0 error 14 in locale-archive[7f184d344000+2ce000]

lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 15.10
Release: 15.10
Codename: wily

[Daniel Verite (dverite)]

I think the bug is related to https://bugreports.qt.io/browse/QTBUG-48709
It happens when a QApplication has been instantiated but its destructor is not called before the atexit() handlers, i.e. the code terminates through exit() without cleaning up.
In the core file, the call stack is smashed.

I don't know what particular program does that in a KUbuntu login sequence, though. If dmesg doesn't tell, maybe core files should be activated and inspected after the fact, just to get the name of the executable.

[Daniel Verite (dverite)]

I forgot that bit in the previous comment: if someone wants to reproduce this, be aware you should retry.
The SIGSEGV happens randomly. For my app where I tracked down the problem, it seems to happen ~2-3 times in 10 tries.

[Robert Dvoracek (lightningstalker)]

Occurs in Mint 18.2, kdenlive 4:15.12.3-0u