From de4d2106f88ad7d98bf3adc602885d1d9071b644 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 18 Sep 2017 17:27:34 +0100 Subject: [PATCH] drm/i915: Check waiter->seqno carefully in case of preemption MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit If preemption occurs at precisely the right moment, we may decide that the wait is complete even though the wait's request is no longer executing (having been preempted). We handle this situation by double checking that request following deciding whether the wait is complete. Reported-by: Michał Winiarski Signed-off-by: Chris Wilson Cc: Michał Winiarski Cc: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20170918162734.21294-2-chris@chris-wilson.co.uk Reviewed-by: Michał Winiarski --- drivers/gpu/drm/i915/i915_irq.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index 2190e42ba310..bd38c6983eec 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -1053,10 +1053,13 @@ static void notify_ring(struct intel_engine_cs *engine) */ if (i915_seqno_passed(intel_engine_get_seqno(engine), wait->seqno)) { + struct drm_i915_gem_request *waiter = wait->request; + wakeup = true; if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, - &wait->request->fence.flags)) - rq = i915_gem_request_get(wait->request); + &waiter->fence.flags) && + intel_wait_check_request(wait, waiter)) + rq = i915_gem_request_get(waiter); } if (wakeup) -- 2.30.2