On Thu, Nov 16, 2023 at 10:20:41AM +0800, Li RongQing wrote:
>there is rare possibility that conn->tx_pushing is not 1, since
>tx_pushing is just checked with 1, so move the setting tx_pushing
>to 1 after atomic_dec_and_test() return false, to avoid atomic_set
>and smp_wmb in tx path
>
>Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
Reviewed-by: Dust Li <dust.li@xxxxxxxxxxxxxxxxx>
>---
> net/smc/smc_tx.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
>diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c
>index 3b0ff3b..72dbdee 100644
>--- a/net/smc/smc_tx.c
>+++ b/net/smc/smc_tx.c
>@@ -667,8 +667,6 @@ int smc_tx_sndbuf_nonempty(struct smc_connection *conn)
> return 0;
>
> again:
>- atomic_set(&conn->tx_pushing, 1);
>- smp_wmb(); /* Make sure tx_pushing is 1 before real send */
> rc = __smc_tx_sndbuf_nonempty(conn);
>
> /* We need to check whether someone else have added some data into
>@@ -677,8 +675,11 @@ int smc_tx_sndbuf_nonempty(struct smc_connection *conn)
> * If so, we need to push again to prevent those data hang in the send
> * queue.
> */
>- if (unlikely(!atomic_dec_and_test(&conn->tx_pushing)))
>+ if (unlikely(!atomic_dec_and_test(&conn->tx_pushing))) {
>+ atomic_set(&conn->tx_pushing, 1);
>+ smp_wmb(); /* Make sure tx_pushing is 1 before real send */
nit: it would be better if we change the comments to "send again".
Thanks
> goto again;
>+ }
>
> return rc;
> }
>--
>2.9.4
