Comment # 24 on bug 904097 from Bruno Pesavento

Created attachment 615540 [details]
Kernel trace pre and post system freeze

Hi, since I see no answer to your request, I attach the kernel trace I got in
what seems the same bug, or at least gives the same end result: black screen,
unresponsive keyboard, only way out forcing power down.
Feel free to discard if you think this is something different.
This happens in OS 13.2 X86_64 Gnome, Core2Duo and Intel 965GM laptop (HP
6510b).
The attached trace was on Kernel 3.16.6-2-desktop with your
i915-kmp-desktop-3.16_k3.16.6_2-4.1.x86_64 but I saw no visible difference on
3.17.3 or 3.17.4 from Kernel:stable.

To reproduce: Login user 1000 (grabs VT7 as usual); switch user;
Login user 1001 (grabs VT2 or VT3, I expected VT8), it works as usual; Logout
(system freezes as described in this bug).
Reproducible: always.
Same freeze trying to switch to VT7 again instead of logging out user 1001.

Sometimes the system freezes gracefully enough to record a kernel trace
according to your hint; attached is the best record I got out of some 20 tries.
@23:09:13 is a kernel trace with user 1001 working as usual.
@23:10:54 user 1001 (mmouse) logs out.
@23:11:04 is a kernel trace with the system frozen; I hope it helps (almost
meaningless to me...)

It seems that gdm-Xorg-:1[1870] on VT2 segfaults on logout of user 1001 and
control is never returned to the gdm-Xorg-:0[851] serving user 1000 on VT7.
The system keyboard is not exactly "dead", since sysrq commands get through, as
do commands from wifi key etc. as originally reported.
Ready to do more testing if needed.