On 16/03/2017 14:53, Chris Wilson wrote:
Do an early read of the execlists' queue before we take the spinlock and start checking. This is safe as the first writer to the execlists queue will cause the tasklet to be run again after a memory barrier.
Which one is the memory barrier, tasklet_hi_schedule? Wouldn't we need an explicit one after setting engine->execlist_first in execlists_submit_request now?
Regards, Tvrtko
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> Cc: Michał Winiarski <michal.winiarski@xxxxxxxxx> --- With the plan to kick the tasklet before it is ready, eliminating a few of the heavier checks seems sensible. -Chris --- drivers/gpu/drm/i915/intel_lrc.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index 89f38e7def9f..17342bc939ad 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -402,6 +402,9 @@ static void execlists_dequeue(struct intel_engine_cs *engine) struct rb_node *rb; bool submit = false; + if (!READ_ONCE(engine->execlist_first)) + return; + last = port->request; if (last) /* WaIdleLiteRestore:bdw,skl
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