Re: [PATCH] block: insert a general SMP memory barrier before wake_up_bit()

[Jacob Wen]

On 8/13/20 3:31 PM, Christoph Hellwig wrote:
On Thu, Aug 13, 2020 at 10:44:38AM +0800, Jacob Wen wrote:
wake_up_bit() uses waitqueue_active() that needs the explicit smp_mb().
Sounds like the barrier should go into wake_up_bit then..

wake_up_bit() doesn't know which one to chose: smp_mb__after_atomic() or 
smp_mb().


Signed-off-by: Jacob Wen <jian.w....@oracle.com>
---
  fs/block_dev.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 0ae656e022fd..e74980848a2a 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1175,6 +1175,7 @@ static void bd_clear_claiming(struct block_device *whole, 
void *holder)
        /* tell others that we're done */
        BUG_ON(whole->bd_claiming != holder);
        whole->bd_claiming = NULL;
+       smp_mb();
        wake_up_bit(&whole->bd_claiming, 0);
  }
  
--
2.17.1

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