From de4d2106f88ad7d98bf3adc602885d1d9071b644 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Mon, 18 Sep 2017 17:27:34 +0100
Subject: [PATCH] drm/i915: Check waiter->seqno carefully in case of preemption
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Git-commit: de4d2106f88ad7d98bf3adc602885d1d9071b644
Patch-mainline: v4.15-rc1
References: FATE#322643 bsc#1055900
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 <michal.winiarski@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170918162734.21294-2-chris@chris-wilson.co.uk
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/i915_irq.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
--- 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_eng
*/
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)