Created attachment 120860 [details]
dmesg output after crash

The system randomly freezes. I can still move the mouse but can't do anything
else. I cannot switch VT, the three-finger salute does not work and system shut
down via ACPI does not work either. The only way of recovery is a hard switch
off.

The crash seems to occur more frequently, if I play videos (mplayer or Flash),
but this is not a requirement.

The crash does not occur, if I use the blob firmware
(nouveau.config="NvGrUseFw=1").

Graphic card: "ASUS GeForce GTX 660 PCI 3.0 2GB DDR5"

uname: "Linux 4.1.12-gentoo #2 SMP Wed Dec 23 19:28:09 CET 2015 x86_64 Intel(R)
Xeon(R) CPU E3-1230 v3 @ 3.30GHz GenuineIntel GNU/Linux"

Beginning of dmesg:

Jan 06 16:04:24 matthias-pc kernel: nouveau E[   PFIFO][0000:01:00.0]
SCHED_ERROR [ CTXSW_TIMEOUT ]
Jan 06 16:04:24 matthias-pc kernel: nouveau E[   PFIFO][0000:01:00.0] PGRAPH
engine fault on channel 2, recovering...
Jan 06 16:04:31 matthias-pc kernel: nouveau E[  PGRAPH][0000:01:00.0] TRAP ch 5
[0x023f926000 kwin[606]]
Jan 06 16:04:31 matthias-pc kernel: nouveau E[  PGRAPH][0000:01:00.0] ROP0
0x80000000 0x80000001
Jan 06 16:04:31 matthias-pc kernel: nouveau E[  PGRAPH][0000:01:00.0] ROP1
0x80000000 0x80000001
Jan 06 16:04:31 matthias-pc kernel: nouveau E[  PGRAPH][0000:01:00.0] ROP2
0x80000000 0x80000001

For a complete log and more system information see the attached files.