The most common situation for this hang is a compiz desktop wall plugin-based viewport switch between workspaces, but I’ve observed it (rarely) in other situations. The symptom is that the screen freezes mid-animation, the compiz process goes to 100+% cpu, and dmesg outputs one or more of the following message:
[1298393.855931] NVRM: Xid (0000:01:00): 56, CMDre 00000001 00000080 00000000 00000005 00000006 [1298393.855943] NVRM: Xid (0000:01:00): 56, CMDre 00000002 00000080 00000000 00000005 00000006
It never recovers by itself, though it appears to try as often the mouse cursor will begin moving again and a frame or two of screen update happens. Sometimes C-A-F1 will work, letting me kill compiz. Otherwise, ssh from another machine works to recover.
The attachment includes several such hangs with compiz-kill-restart sessions.
Hardware is a single GTX285 driving two monitors 1920x1200 in TwinView mode.
nvidia-bug-report.log.gz (76.7 KB)