From 2d453c7895c0ca6028500050ff9305c70fd7252f Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Fri, 22 Dec 2017 14:19:59 +0000
Subject: [PATCH] drm/i915: Assert that the request is on the execution queue before being removed
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Git-commit: 2d453c7895c0ca6028500050ff9305c70fd7252f
Patch-mainline: v4.16-rc1
References: FATE#322643 bsc#1055900

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 engine, it must have a zero global_seqno or else we are queuing
the same request twice.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171222141959.3006-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/i915_gem_request.c |    2 ++
 1 file changed, 2 insertions(+)

--- 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 dr
 	/* 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
 	/* 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--;