nouveau X lockup on 36-rc (regression from 2.6.35)

[Johannes Berg]

On Wed, 2010-08-25 at 15:55 +0200, Johannes Berg wrote:
> Since 2.6.36-rc kernels (both rc1 and rc2) I've had X lockups where X
> sits in a loop just using CPU.
> 
> The only kernel message I got this time was this one:
> 
> [22290.792075] [drm] nouveau 0000:02:00.0: PFIFO_DMA_PUSHER - Ch 2
> 
> stracing X just repeats, in a loop,
> 
> ioctl(9, 0x40086482, 0x7fff6a873af0)    = ? ERESTARTSYS (To be restarted)
> --- SIGALRM (Alarm clock) @ 0 (0) ---
> rt_sigreturn(0xe)                       = -1 EINTR (Interrupted system call)
> 
> 
> so apparently that ioctl never returns.
> 
> This has never happened on 2.6.35, and I've gone back now. Large screen
> updates seem to trigger it more likely, but I haven't found a way to
> really reproduce it. FWIW, I'm running with two screens connected.

This problem persists in -rc3, where I'd hoped the nouveau changes would
actually fix it :-( In fact, it seems I was either "lucky" or it was
made easier to trigger, this time it already happened during my login.

johannes