[Intel-gfx] [PATCH v3 7/8] drm/i915: Grab execlist spinlock to avoid post-reset concurrency issues.

[Tomas Elf]

Grab execlist lock when cleaning up execlist queues after GPU reset to avoid
concurrency problems between the context event interrupt handler and the reset
path immediately following a GPU reset.

* v2 (Chris Wilson):
Do execlist check and use simpler form of spinlock functions.

* v3 (Tvrtko Ursulin):
Don't hold the execlist_lock while dereferencing the requests since that might
lead to sleep while IRQs are disabled.

Signed-off-by: Tomas Elf <tomas.elf at intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>

---
 drivers/gpu/drm/i915/i915_gem.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index e57061a..b492603 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2753,18 +2753,16 @@ static void i915_gem_reset_ring_cleanup(struct drm_i915_private *dev_priv,
 	 * are the ones that keep the context and ringbuffer backing objects
 	 * pinned in place.
 	 */
-	while (!list_empty(&ring->execlist_queue)) {
-		struct drm_i915_gem_request *submit_req;
 
-		submit_req = list_first_entry(&ring->execlist_queue,
-				struct drm_i915_gem_request,
-				execlist_link);
-		list_del(&submit_req->execlist_link);
+	if (i915.enable_execlists) {
+		spin_lock_irq(&ring->execlist_lock);
 
-		if (submit_req->ctx != ring->default_context)
-			intel_lr_context_unpin(submit_req);
+		/* list_splice_tail_init checks for empty lists */
+		list_splice_tail_init(&ring->execlist_queue,
+				      &ring->execlist_retired_req_list);
 
-		i915_gem_request_unreference(submit_req);
+		spin_unlock_irq(&ring->execlist_lock);
+		intel_execlists_retire_requests(ring);
 	}
 
 	/*
-- 
1.9.1