[Intel-gfx] [PATCH] drm/i915/gt: Add one more rcu_barrier() after draining the ppGTT freelist

[Chris Wilson]

Since gen7 full-ppgtt uses nested vm references (the ppGTT is a slot
within the global GTT and so has a buried i915_ggtt) we may need to go
through a couple of RCU barriers before we have freed all the structs.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_ggtt.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c b/drivers/gpu/drm/i915/gt/intel_ggtt.c
index 894d08e5a21f..cb31ed712db3 100644
--- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
@@ -684,8 +684,9 @@ static void ggtt_cleanup_hw(struct i915_ggtt *ggtt)
 
 	atomic_set(&ggtt->vm.open, 0);
 
-	rcu_barrier(); /* flush the RCU'ed__i915_vm_release */
-	flush_workqueue(ggtt->vm.i915->wq);
+	do { /* flush the RCU'ed__i915_vm_release */
+		rcu_barrier();
+	} while (flush_workqueue(ggtt->vm.i915->wq));
 
 	mutex_lock(&ggtt->vm.mutex);
 
-- 
2.20.1