On Thu, Jul 09, 2015 at 04:07:05PM +0100, Chris Wilson wrote: > On Thu, Jul 09, 2015 at 03:30:57PM +0100, Tomas Elf wrote: > > The hang checker needs to inspect whether or not the ring request list is empty > > as well as if the given engine has reached or passed the most recently > > submitted request. The problem with this is that the hang checker cannot grab > > the struct_mutex, which is required in order to safely inspect requests since > > requests might be deallocated during inspection. In the past we've had kernel > > panics due to this very unsynchronized access in the hang checker. > > > > One solution to this problem is to not inspect the requests directly since > > we're only interested in the seqno of the most recently submitted request - not > > the request itself. Instead the seqno of the most recently submitted request is > > stored separately, which the hang checker then inspects, circumventing the > > issue of synchronization from the hang checker entirely. > > > > v2 (Chris Wilson): > > - Pass current engine seqno to ring_idle() from i915_hangcheck_elapsed() rather > > than compute it over again. > > - Remove extra whitespace. > > > > Issue: VIZ-5998 > > Signed-off-by: Tomas Elf <tomas.elf@xxxxxxxxx> > > Yup, that is a nice simple fix by partially reverting the > s/seqno/requests/ change (and improving upon it in the process). > > We should mention > > Fixes commit 44cdd6d219bc64f6810b8ed0023a4d4db9e0fe68 > Author: John Harrison <John.C.Harrison@xxxxxxxxx> > Date: Mon Nov 24 18:49:40 2014 +0000 > > drm/i915: Convert 'ring_idle()' to use requests not seqnos > > and > Cc: stable@xxxxxxxxxxxxxxx > Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Added and applied to -fixes, thanks. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
