drm/i915/gt: Check the virtual still matches upon locking

If another sibling is able to claim the virtual request, by the time we
inspect the request under the lock it may no longer match the local
engine.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2877
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210104115145.24460-4-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
index f02e3ae..a5b4426 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
+++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
@@ -1016,6 +1016,9 @@ static bool virtual_matches(const struct virtual_engine *ve,
 {
        const struct intel_engine_cs *inflight;
 
+       if (!rq)
+               return false;
+
        if (!(rq->execution_mask & engine->mask)) /* We peeked too soon! */
                return false;
 
@@ -1423,8 +1426,8 @@ check_secondary:
                spin_lock(&ve->base.active.lock);
 
                rq = ve->request;
-               if (unlikely(!rq)) /* lost the race to a sibling */
-                       goto unlock;
+               if (unlikely(!virtual_matches(ve, rq, engine)))
+                       goto unlock; /* lost the race to a sibling */
 
                GEM_BUG_ON(rq->engine != &ve->base);
                GEM_BUG_ON(rq->context != &ve->context);
@@ -1434,8 +1437,6 @@ check_secondary:
                        break;
                }
 
-               GEM_BUG_ON(!virtual_matches(ve, rq, engine));
-
                if (last && !can_merge_rq(last, rq)) {
                        spin_unlock(&ve->base.active.lock);
                        spin_unlock(&engine->active.lock);