On Mon, May 12, 2014 at 09:05:45AM +0000, Mateo Lozano, Oscar wrote: > Hi Daniel, > > Sorry, this fell through the cracks: > > > Subject: Re: [PATCH] drm/i915: Gracefully handle obj not bound to > > GGTT in is_pin_display > > > > On Wed, Apr 02, 2014 at 07:21:01PM +0100, oscar.mateo@xxxxxxxxx wrote: > > > From: Oscar Mateo <oscar.mateo@xxxxxxxxx> > > > > > > Otherwise, we do a NULL pointer dereference. > > > > > > I've seen this happen while handling an error in > > > i915_gem_object_pin_to_display_plane(): > > > > > > If i915_gem_object_set_cache_level() fails, we call is_pin_display() > > > to handle the error. At this point, the object is still not pinned to > > > GGTT and maybe not even bound, so we have to check before we > > > dereference its GGTT vma. > > > > > > Issue: VIZ-3772 > > > Signed-off-by: Oscar Mateo <oscar.mateo@xxxxxxxxx> > > > > Have you looked into provoking this with an igt testcase? On a hunch a busy > > load (to extend the race window) plus the usual interruptor trick to jump out of > > wait_seqno calls should be able to make this go kaboom on command. But I > > haven't analyzed the bug in detail. > > AFAICT, the only sequence where this likely to happen (because we are handling a recently created object) is: > > intelfb_alloc -> intel_pin_and_fence_fb_obj -> i915_gem_object_pin_to_display_plane -> i915_gem_object_set_cache_level -> is_pin_display > > Now, I think intelfb_alloc only happens during bootup, so reproducing it on IGT would be difficult. > I still feel the fix is valid though :) Did you consider my alternative fix of restoring the old value in the error path? -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
