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> Regards, Joonas -- Joonas Lahtinen Open Source Technology Center Intel Corporation _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
