[Intel-gfx] [PATCH] drm/i915: Wait upon the last request seqno, rather than a future seqno

[Chris Wilson]

In commit 69c2fc891343cb5217c866d10709343cff190bdc
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Fri Jul 20 12:41:03 2012 +0100

    drm/i915: Remove the per-ring write list

the explicit flush was removed from i915_ring_idle(). However, we
continued to wait upon the next seqno which now did not correspond to
any request (except for the unusual condition of a failure to queue a
request after execbuffer) and so would wait indefinitely.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem.c |   24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 94a9ada..39de523 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2596,16 +2596,24 @@ static int i915_ring_idle(struct intel_ring_buffer *ring)
 	u32 seqno;
 	int ret;
 
-	if (list_empty(&ring->active_list))
-		return 0;
+	/* We need to add any requests required to flush the objects */
+	if (!list_empty(&ring->active_list)) {
+		seqno = list_entry(ring->active_list.prev,
+				   struct drm_i915_gem_object,
+				   ring_list)->last_read_seqno;
 
-	seqno = list_last_entry(&ring->active_list,
-				struct drm_i915_gem_object,
-				ring_list)->last_read_seqno;
+		ret = i915_gem_check_olr(ring, seqno);
+		if (ret)
+			return ret;
+	}
 
-	ret = i915_gem_check_olr(ring, seqno);
-	if (ret)
-		return ret;
+	/* Wait upon the last request to be completed */
+	if (list_empty(&ring->request_list))
+		return 0;
+
+	seqno = list_entry(ring->request_list.prev,
+			   struct drm_i915_gem_request,
+			   list)->seqno;
 
 	return i915_wait_seqno(ring, seqno);
 }
-- 
1.7.10.4