Happens to me as well since I updated my system two or three days ago. I'd assume this was caused by a recent package change.

I'm using Antergos amd64 on a HP Pavilion laptop. As for bringing something useful to the table:



### This is dmesg: ###


[ 1815.769256] kactivitymanage[2625]: segfault at 7fa3582f1d10 ip 00007fa35853c881 sp 00007ffd59611418 error 4 in libQt5Sql.so.5.5.0[7fa358526000+41000]

-----------
So same as OP.  Note that kactivitymanager is not the thing that crashes Xorg (I removed the x permission from /usr/bin/kactivitymanager — crashes still happen, but there's nothing in dmesg anymore). This also appears to happen slightly AFTER X crashes (look at the timestamps below).



### This is in the /var/log/Xorg.0.log[.old] file: ###

[ 1815.211] (EE)
[ 1815.211] (EE) Backtrace:
[ 1815.244] (EE) 0: /usr/lib/xorg-server/Xorg (OsLookupColor+0x139) [0x596cf9]
[ 1815.259] (EE) 1: /usr/lib/libc.so.6 (__restore_rt+0x0) [0x7f1f140ea5af]
[ 1815.259] (EE) 2: /usr/lib/xorg-server/Xorg (FlushAllOutput+0xa6) [0x596196]
[ 1815.259] (EE) 3: /usr/lib/xorg-server/Xorg (SendErrorToClient+0x20a) [0x438d5a]
[ 1815.260] (EE) 4: /usr/lib/xorg-server/Xorg (remove_fs_handlers+0x41b) [0x43cf4b]
[ 1815.260] (EE) 5: /usr/lib/libc.so.6 (__libc_start_main+0xf0) [0x7f1f140d7790]
[ 1815.260] (EE) 6: /usr/lib/xorg-server/Xorg (_start+0x29) [0x427319]
[ 1815.261] (EE) 7: ? (?+0x29) [0x29]
[ 1815.261] (EE)
[ 1815.261] (EE) Segmentation fault at address 0x4941ba0
[ 1815.261] (EE)
Fatal server error:
[ 1815.261] (EE) Caught signal 11 (Segmentation fault). Server aborting
[ 1815.261] (EE)
[ 1815.261] (EE)
Please consult the The X.Org Foundation support
at http://wiki.x.org
for help.
[ 1815.261] (EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information.
[ 1815.261] (EE)
[ 1815.261] (II) AIGLX: Suspending AIGLX clients for VT switch
[ 1815.270] (EE) Server terminated with error (1). Closing log file.

@Viktor - can you please post /var/log/Xorg.0.log and /var/log/Xorg.0.log.old the next time you get the crash? 







I did some further digging around the internet. The more I look around, the more it seems that crashes aren't necessarily a KDE bug crashing X, but a Xorg issue which causes libQt5Sql and kactivitymanager to crash.

On Arch forums: https://bbs.archlinux.org/viewtopic.php?id=199812 (OP there has intel, I have radeon, someone in the thread also mentions radeon)

Here’s the freedesktop bug report mentioned in the Arch forum thread: https://bugs.freedesktop.org/show_bug.cgi?id=89898

I'll try and check if bug (random crashes) are present on a different DE. If they are, then KDE is probably the wrong tree to bark at.

Same here. My laptop is running Archlinux x86_64 with Intel Core i5 4200U.

+1 for "the bug seems to appear after an update and therefore may be due to a recent package change"

Same here. X keeps crashing every 5-10 minutes.

kactivitymanage[720]: segfault at 7f2ac5540d10 ip 00007f2ac578b881 sp 00007fffb6881ce8 error 4 in libQt5Sql.so.5.5.0[7f2ac5775000+41000]
[ 8570.771413] kactivitymanage[12604]: segfault at 7f2209d41d10 ip 00007f220b198881 sp 00007ffec3690038 error 4 in libQt5Sql.so.5.5.0[7f220b182000+41000]
[ 8843.378108] kactivitymanage[9626]: segfault at 7f8ee716fd10 ip 00007f8ef4646881 sp 00007ffcf4368038 error 4 in libQt5Sql.so.5.5.0[7f8ef4630000+41000]
[ 9738.732253] kactivitymanage[11489]: segfault at 7fef50917d10 ip 00007fef51d6e881 sp 00007ffe94694298 error 4 in libQt5Sql.so.5.5.0[7fef51d58000+41000]

I'm with Nvidia and KDE 4.

Linux mozo 4.1.2-2-ARCH #1 SMP PREEMPT Wed Jul 15 08:30:32 UTC 2015 x86_64 GNU/Linux

I'm investigating problem further. It seems that I was too fast to open bug here.
Xorg log attached. I have one question to others with such bug: what kernel version do you use ?
I had several crashed on KDE4 before. And the cause was i915 crash according to dmesg.... And it was 4.1.x kernel. There was no such problems before. I will downgrade my kernel to 4.0.x and will try to test.

From Xorg.0.log.old:
[  4474.394] (EE) Backtrace:
[  4474.394] (EE) 0: /usr/bin/X (xorg_backtrace+0x56) [0x58acc6]
[  4474.394] (EE) 1: /usr/bin/X (0x400000+0x18ef69) [0x58ef69]
[  4474.394] (EE) 2: /lib64/libc.so.6 (0x7f977f752000+0x33aa0) [0x7f977f785aa0]
[  4474.394] (EE) 3: /usr/bin/X (FlushAllOutput+0xc0) [0x58e5a0]
[  4474.395] (EE) 4: /usr/bin/X (WaitForSomething+0x635) [0x5882f5]
[  4474.395] (EE) 5: /usr/bin/X (0x400000+0x37b71) [0x437b71]
[  4474.395] (EE) 6: /usr/bin/X (0x400000+0x3be7b) [0x43be7b]
[  4474.395] (EE) 7: /lib64/libc.so.6 (__libc_start_main+0xf0) [0x7f977f771fa0]
[  4474.395] (EE) 8: /usr/bin/X (0x400000+0x2638e) [0x42638e]
[  4474.395] (EE)
[  4474.395] (EE) Segmentation fault at address 0x3941e12f8

I'm with 4.1.2-2. Downgrading xorg don't help at all.

And my system is nearly unusable.

Are you sure downgrading xorg does not help ?
I have found that link: https://www.mail-archive.com/arch-commits@archlinux.org/msg219063.html
It looka like a fix 'FlushAllOutput' function in xorg. Will try to patch my xorg right now.

It deludes me because of crash which is Pale Moon and fresh player related and it happens after I have downgraded xorg. In fact downgrading xorg works. Sorry, my fault.

It seems that this was a bug of 1.7.2 xorg. I've patched my install and testing. Anyway I think this bug should be closed.

Why close? It crashes even with latest 1.7.2-2...

Little mistake: i'm talking about bug in 1.17.2 version. Fix will be introduced in arch in 1.17.2-4 xorg-server package - I found it on mailing list today. Also according to logs bug is really not related to kactivities.