[PATCH] drm/i915: Fix use of invalid array size for ring->sync_seqno

[Chris Wilson]

There are I915_NUM_RINGS-1 inter-ring synchronisation counters, but we
were clearing I915_NUM_RINGS of them. Oops.

Reported-by: Jiri Slaby <jirislaby@xxxxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---

Jiri, does this catch the invalid array access? For 3 rings, there should
only be 2 sync counters...

---
 drivers/gpu/drm/i915/i915_gem.c            |    2 +-
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 3dfc848..812b97b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1857,7 +1857,7 @@ i915_gem_retire_requests_ring(struct drm_device *dev,
 
 	seqno = ring->get_seqno(ring);
 
-	for (i = 0; i < I915_NUM_RINGS; i++)
+	for (i = 0; i < ARRAY_SIZE(ring->sync_seqno); i++)
 		if (seqno >= ring->sync_seqno[i])
 			ring->sync_seqno[i] = 0;
 
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index dcfdf41..d2f445e 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1175,7 +1175,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 		goto err;
 
 	seqno = i915_gem_next_request_seqno(dev, ring);
-	for (i = 0; i < I915_NUM_RINGS-1; i++) {
+	for (i = 0; i < ARRAY_SIZE(ring->sync_seqno); i++) {
 		if (seqno < ring->sync_seqno[i]) {
 			/* The GPU can not handle its semaphore value wrapping,
 			 * so every billion or so execbuffers, we need to stall
-- 
1.7.2.3

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