From 4f6d8fcf1a53d4d544d9a13f70cb2669572b7ecb Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 7 May 2018 14:57:25 +0100 Subject: [PATCH] drm/i915: Flush submission tasklet after bumping priority When called from process context tasklet_schedule() defers itself to ksoftirqd. From experience this may cause unacceptable latencies of over 200ms in executing the submission tasklet, our goal is to reprioritise the HW execution queue and trigger HW preemption immediately, so disable bh over the call to schedule and force the tasklet to run afterwards if scheduled. v2: Keep rcu_read_lock() around for PREEMPT_RCU Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Mika Kuoppala Link: https://patchwork.freedesktop.org/patch/msgid/20180507135731.10587-1-chris@chris-wilson.co.uk Reviewed-by: Tvrtko Ursulin --- drivers/gpu/drm/i915/i915_gem.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 5ece6ae4bdff..89bf5d67cb74 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -578,10 +578,12 @@ static void __fence_set_priority(struct dma_fence *fence, rq = to_request(fence); engine = rq->engine; - rcu_read_lock(); + local_bh_disable(); + rcu_read_lock(); /* RCU serialisation for set-wedged protection */ if (engine->schedule) engine->schedule(rq, attr); rcu_read_unlock(); + local_bh_enable(); /* kick the tasklets if queues were reprioritised */ } static void fence_set_priority(struct dma_fence *fence,