On Thu, 3 Jul 2014 16:51:11 +0100 Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > On Thu, Jul 03, 2014 at 08:44:20AM -0700, Jesse Barnes wrote: > > On Thu, 3 Jul 2014 08:09:01 +0100 > > Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > > > > > Since we rely on hangcheck to wait up and kick us out of an indefinite > > > wait should the GPU ever stop functioning, it appears sensible that we > > > should check that hangcheck is indeed active before starting that wait. > > > This just prevents a driver error in the processing of hangcheck from > > > appearing to hang the machine. > > > Are there any bugs associated with this? > > No open bugs. They have cropped up during dev though, and I think I am > not alone. I believe that both Ben and I have tried to convince Daniel > the merits of having this security blanket. > > > i915_rearm_hangcheck() or something might more accurately describe > > what's going on here. > > How about i915_ensure_hangcheck()? (I agree that rearm is better than > check.) > > > I suppose both of these paths are protected by the struct_mutex? If > > not, might we race and mod_timer() this twice from two threads in > > succession? I guess that's harmless... > > Concurrently arming a timer within a jiffie or two isn't going to make > too much difference, or even pushing an almost firing timer off by > another hangcheck interval. Conversely, since we already have read the > hangcheck counter, if the hangcheck does fire before we schedule(), that > will immediately wake us up and we will spot the hang. Sounds good. ensure_hangcheck() or update_hangcheck() are fine with me too. Reviewed-by: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx> -- Jesse Barnes, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
