[Intel-gfx] [PATCH v2] drm/i915: Assert that the context pin_counts do not overflow

[Chris Wilson]

This should be impossible, but let's assert that we do not pin a context
4 billion times before retiring!

v2: Fix the assertion -- the patch had just one job to do!

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala at intel.com>
---
 drivers/gpu/drm/i915/intel_lrc.c        | 1 +
 drivers/gpu/drm/i915/intel_ringbuffer.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 73386b7b22fa..aad107337530 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -748,6 +748,7 @@ static int execlists_context_pin(struct intel_engine_cs *engine,
 
 	if (ce->pin_count++)
 		return 0;
+	GEM_BUG_ON(!ce->pin_count); /* no overflow please! */
 
 	if (!ce->state) {
 		ret = execlists_context_deferred_alloc(ctx, engine);
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index e895c99f5dd9..be908e2a52ea 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1445,6 +1445,7 @@ static int intel_ring_context_pin(struct intel_engine_cs *engine,
 
 	if (ce->pin_count++)
 		return 0;
+	GEM_BUG_ON(!ce->pin_count); /* no overflow please! */
 
 	if (ce->state) {
 		ret = context_pin(ctx);
-- 
2.11.0