Comment 9 for bug 1291574

I believe I encountered the same issue while working on bug #1412602 which is unrelated to this bug.

In the process of testing the nouveau driver with an nVidia C61 [GeForce 7025 / nForce 630a] chipset on Ubuntu GNOME Trusty with the Utopic HWE and 3.16.0-31-generic from trusty-proposed I experienced what I'd call a soft-lockup (I could still move the mouse pointer but all else was unresponsive) and after a minute or two the screen went basically blank with this message sprawled across the screen:

[ 1206.026900] nouveau E[ DRM] GPU lockup - switching to software fbcon

[ 1305.160013] nouveau E[Xorg[955]] failed to idle channel 0xeeee0000 [Xorg[955]]

[ 1320.160018] nouveau E[Xorg[955]] failed to idle channel 0xeeee0000 [Xorg[955]]

[ 1328.076012] BUG: soft lockup - GPU#0 stuck for 21sf [gnome-shell:1740]

After reboot I found a crash report in /var/log/crash but it was unreportable, the details say:

This problem report is damaged and cannot be processed.

EOF Error('Compressed file ended before the end-of-stream marker was reached',)

I'm attaching a picture of the screen during freeze.