As we use a mutex to serialise the first acquire (as it may be a lengthy
operation), but only an atomic decrement for the release, we have to
be careful in case a second thread races and completes both
acquire/release as the first finishes its acquire.
Fixes: c9ad602feabe ("drm/i915: Split i915_active.mutex into an irq-safe spinlock for the rbtree")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_active.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
index ace55d5d4ca7..9d6830885d2e 100644
--- a/drivers/gpu/drm/i915/i915_active.c
+++ b/drivers/gpu/drm/i915/i915_active.c
@@ -416,13 +416,15 @@ int i915_active_acquire(struct i915_active *ref)
if (err)
return err;
- if (!atomic_read(&ref->count) && ref->active)
- err = ref->active(ref);
- if (!err) {
- spin_lock_irq(&ref->tree_lock); /* vs __active_retire() */
- debug_active_activate(ref);
- atomic_inc(&ref->count);
- spin_unlock_irq(&ref->tree_lock);
+ if (likely(!i915_active_acquire_if_busy(ref))) {
+ if (ref->active)
+ err = ref->active(ref);
+ if (!err) {
+ spin_lock_irq(&ref->tree_lock); /* __active_retire() */
+ debug_active_activate(ref);
+ atomic_inc(&ref->count);
+ spin_unlock_irq(&ref->tree_lock);
+ }
}
mutex_unlock(&ref->mutex);
--
2.25.0
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