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
Reviewed-by: Dust Li <dust.li@xxxxxxxxxxxxxxxxx>
Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
---
diff v3: improvements in the commit body and comments
diff v2: fix a typo in commit body and add net-next subject-prefix
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..2c2933f 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 send again */
goto again;
+ }
return rc;
}
--
2.9.4
