As the set of shared fences is not being changed during reallocation of
the reservation list, we can skip updating the write_seqlock.
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vet...@ffwll.ch>
Cc: Christian König <christian.koe...@amd.com>
---
drivers/dma-buf/reservation.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
index 80ecc1283d15..c71b85c8c159 100644
--- a/drivers/dma-buf/reservation.c
+++ b/drivers/dma-buf/reservation.c
@@ -157,15 +157,15 @@ 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; both existing
+ * readers and new readers will see exactly the same set of
+ * active (unsignaled) shared fences. 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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