[Intel-gfx] [drm:i915_gem_mmap_gtt_ioctl] *ERROR* Attempting to mmap a purgeable buffer

[Chris Wilson]

On Wed, 20 Oct 2010 11:07:20 +0200, Alexey Fisher <bug-track at fisher-privat.net> wrote:
> Hallo all,
> 
> I get fallowing error in my log:
> [ 6657.465805] [drm:i915_gem_mmap_gtt_ioctl] *ERROR* Attempting to mmap
> a purgeable buffer
> [ 6657.465851] [drm:i915_gem_mmap_gtt_ioctl] *ERROR* Attempting to mmap
> a purgeable buffer
> [ 6657.465907] [drm:i915_gem_mmap_gtt_ioctl] *ERROR* Attempting to mmap
> a purgeable buffer
> 
> das it mean any thing for you? do i need to bisect it?
> I use current 2.6.36-rc8-01141-ga5ffe0a from intel drm next.

It's warning that userspace is breaking the rules and trying to use a
buffer it has declared no longer in use. The challenge is to find the
scenario that is triggering this *userspace* bug.

Currently, purgeable is usually only set on the userspace bo cache, so
this means that we are continuing to use a freed buffer.  Disabling (or
marking the cache as NO_ACCESS) and valgrinding would be a useful step.

Or just kill the userspace cache and implement a kernel uncached page
cache... Less code, more performance, everyone is happy...
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre