On Fri, Apr 07, 2017 at 10:25:13AM +0300, Joonas Lahtinen wrote: > On to, 2017-04-06 at 18:00 +0100, Chris Wilson wrote: > > When we retire the last request on the ring, before we ever access that > > ring again we know it will be completely idle and so we can advance the > > ring->head fully to the end (i.e. ring->tail) and not just to the start > > of the breadcrumb. This allows us to skip re-emitting the breadcrumb > > after resetting the GPU if the ring was entirely idle. This prevents us > > from overwriting a seqno wraparound by re-executing a stale breadcrumb, > > i.e. > > submit_request(1) > > intel_engine_init_global_seqno(0) > > i915_reset() > > would then leave 1 in the HWS, but the next request to execute would > > also be with seqno 1. The sanity checks upon submission detect this as a > > timewarp and explode. By setting the ring as empty, upon reset the HWS > > is left as 0, leaving it consistent with the timeline. > > > > v2: Fix check for deleting last element of list. We know that this > > request is always the first element of the ring, so only if next > > points back to the start will this be the only request in flight. > > v3: Remove opencoding of list_is_last() > > v4: Move the block to its own function for some clarity. > > > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100144 > > Testcase: igt/gem_exec_whisper/hang-* > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxx> > > Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> Thanks for the review, and pushed. One more mysterious reset fix done. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
