[PATCH 2/2] dma-buf: Relax the write-seqlock for reallocating the shared fence list
Chris Wilson
chris at chris-wilson.co.uk
Thu Jul 11 21:19:28 UTC 2019
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
drivers/dma-buf/reservation.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
index 80ecc1283d15..23a644e24608 100644
--- a/drivers/dma-buf/reservation.c
+++ b/drivers/dma-buf/reservation.c
@@ -157,15 +157,13 @@ int reservation_object_reserve_shared(struct reservation_object *obj,
(ksize(new) - offsetof(typeof(*new), shared)) /
sizeof(*new->shared);
- preempt_disable();
- write_seqcount_begin(&obj->seq);
/*
- * RCU_INIT_POINTER can be used here,
- * seqcount provides the necessary barriers
+ * We are not changing the effective set of fences here so can
+ * merely update the pointer to the new array. Individual fences
+ * and the old array are protected by RCU and so will not vanish
+ * under the gaze of the rcu_read_lock() readers.
*/
- RCU_INIT_POINTER(obj->fence, new);
- write_seqcount_end(&obj->seq);
- preempt_enable();
+ rcu_assign_pointer(obj->fence, new);
if (!old)
return 0;
--
2.22.0
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