Bug 46991

If you've had the nvidia module even loaded during a boot then it could easily be responsible. One driver can crash another.

I've seen it crash with the same error without the nvidia module ever being loaded. I only mentioned it because the nvidia module was loaded at the time of the syslog. The nvidia module is blacklisted so that it doesn't get loaded at boot - it only gets loaded if I manually start an X server with it via bumblebee.

Created attachment 79231 [details]
syslog of second crash

Here's a second crash from later today. It looks like the same stack trace (no nvidia module was ever loaded this time).

rocko, I think you'll have to bisect it.

That's a real pity, because I don't know how to reproduce it. For instance, it happened again for the first time since the 4th of September - ie a full 8 days later, so bisecting will take forever. I was hoping the stack trace might be of use.

Created attachment 79861 [details]
another crashlog from 3.6-rc5

Created attachment 80521 [details]
Flush outstanding unpin tasks.

The working theory is that we have a backlog of incomplete pageflip tasks leaking the pincount.

OK, trying the patch out now, so far so good. (But this is a really tricky one to trigger; I don't think I've seen it now in the last 11 days.)

Any sign of success?

Created attachment 83911 [details]
syslog of a crash

I have seen the occasional hang, for instance the attached was from five days ago when running on kernel 3.6.2. There's an intel_unpin_fb_obj call in the stack trace - is that relevant to this bug? 

At the time of this crash I didn't have the patch from this bug applied, it will be a standard kernel. However, I assumed the patch was already sent to git because I had to revert it in an earlier rc when it conflicted with a git update.

Created attachment 83971 [details]
Flush outstanding unpin tasks.

It was never applied as I was waiting for confirmation that it does fix things before yelling at Daniel.

Oops, I guess I should have said something earlier. Is the last crash I attached the same bug then?

Which version of the kernel is the new patch for? I tried it against 3.7-rc1 (my preferred one since it is working quite nicely at the moment) and 3.6.2 and in both cases it failed to apply hunk #2, ie to method do_intel_finish_page_flip. In both cases this line isn't in the method:

 if (atomic_read(&obj->pending_flip) == 0)
  		wake_up(&dev_priv->pending_flip_queue);

Instead, the lines before where it is trying to apply the patch are "atomic_clear_mask(1 << intel_crtc->plane, &obj->pending_flip.counter);" and "wake_up(&dev_priv->pending_flip_queue);".

Should I just replace "schedule_work(&work->work);" with "queue_work(dev_priv->wq, &work->work);"?

(In reply to comment #12)
> Oops, I guess I should have said something earlier. Is the last crash I
> attached the same bug then?

Its close enough that the cause is likely to be the same, but for the moment I'm just a little puzzled by that appearing to be an unpin leak...

> Which version of the kernel is the new patch for? I tried it against 3.7-rc1
> (my preferred one since it is working quite nicely at the moment) and 3.6.2
> and
> in both cases it failed to apply hunk #2, ie to method

It was against dinq, rebasing now against 3.7-rc1 for you.

Created attachment 83981 [details]
Flush outstanding unpin tasks (v3.7-rc1)

Thanks, I've applied it against the latest git and am now trying it out.

So I've been running with the patch against 3.7-rcX for the last four weeks now. Generally it has behaved fine, although I've did seen it crash once - right after the nvidia driver crashed with a Xid error. The syslog looked similar to the previous errors, but I only got a couple of lines of it before the kernel locked up, so it's not any help.

I do find that if I run SNA with the latest video driver (xf86-video-intel-2.6.99.902 at the moment), occasionally unity/compiz locks up after the screen saver - I just get a black screen where only the mouse pointer moves until I restart unity. Is it at all possible that this behaviour is linked to the patch? If I use UXA I get the slightly less annoying glitch where the screen locks up completely at random (again except for the mouse) but I can reset it by CTRL-ALT-F1 and then back again with CTRL-ALT-F7.

(In reply to comment #16)
> I do find that if I run SNA with the latest video driver
> (xf86-video-intel-2.6.99.902 at the moment), occasionally unity/compiz locks
> up
> after the screen saver - I just get a black screen where only the mouse
> pointer
> moves until I restart unity. Is it at all possible that this behaviour is
> linked to the patch? 

No, there are a few other funnies in the kernel eating the pageflip...

A patch referencing this bug report has been merged in Linux v3.8-rc1:

commit b4a98e57fc27854b5938fc8b08b68e5e68b91e1f
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Thu Nov 1 09:26:26 2012 +0000

    drm/i915: Flush outstanding unpin tasks before pageflipping