[PATCH 02/48] drm/i915: Detect potential i915_reset_trylock() lockups

[Chris Wilson]

Use lockdep to warn before we wait indefinitely in case we may be
waiting indefinitely.

Suggested-by: Mika Kuoppala <mika.kuoppala at intel.com>
References: 2caffbf11762 ("drm/i915: Revoke mmaps and prevent access to fence registers across reset")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at intel.com>
---
 drivers/gpu/drm/i915/i915_reset.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reset.c b/drivers/gpu/drm/i915/i915_reset.c
index c1b53533ada6..364c74d1d59b 100644
--- a/drivers/gpu/drm/i915/i915_reset.c
+++ b/drivers/gpu/drm/i915/i915_reset.c
@@ -1305,6 +1305,8 @@ int i915_reset_trylock(struct drm_i915_private *i915)
 	struct i915_gpu_error *error = &i915->gpu_error;
 	int srcu;
 
+	might_lock(&error->reset_backoff_srcu);
+
 	rcu_read_lock();
 	while (test_bit(I915_RESET_BACKOFF, &error->flags)) {
 		rcu_read_unlock();
-- 
2.20.1