[Intel-gfx] [PATCH] drm/i915: Assert that the request is on the execution queue before being removed

[Chris Wilson]

We should only attempt to remove requests from the execution queue that
are on the execution queue. These are the requests that have been
assigned a global_seqno, so we can assert that we only attempt to remove
requests with a nonzero global_seqno. Afterwards we assert that we
remove them in order, i.e. the global_seqno matches the engine's seqno,
but that leaves a small loophole for an unattached request on an unused
engine.

We can then make the same assertion on queuing the request to the
execution, it must have a zero global_seqno or else we are queuing the
same request twice.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Michał Winiarski <michal.winiarski at intel.com>
---
 drivers/gpu/drm/i915/i915_gem_request.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 59f023bb7015..d575109f7a7f 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -479,6 +479,7 @@ void __i915_gem_request_submit(struct drm_i915_gem_request *request)
 	/* Transfer from per-context onto the global per-engine timeline */
 	timeline = engine->timeline;
 	GEM_BUG_ON(timeline == request->timeline);
+	GEM_BUG_ON(request->global_seqno);
 
 	seqno = timeline_get_seqno(timeline);
 	GEM_BUG_ON(!seqno);
@@ -525,6 +526,7 @@ void __i915_gem_request_unsubmit(struct drm_i915_gem_request *request)
 	/* Only unwind in reverse order, required so that the per-context list
 	 * is kept in seqno/ring order.
 	 */
+	GEM_BUG_ON(!request->global_seqno);
 	GEM_BUG_ON(request->global_seqno != engine->timeline->seqno);
 	engine->timeline->seqno--;
 
-- 
2.15.1