On Fri, Mar 15, 2024 at 06:28:38PM +0900, Yewon Choi wrote:
> acquire/release_in_xmit() work as bit lock in rds_send_xmit(), so they
> are expected to ensure acquire/release memory ordering semantics.
> However, test_and_set_bit/clear_bit() don't imply such semantics, on
> top of this, following smp_mb__after_atomic() does not guarantee release
> ordering (memory barrier actually should be placed before clear_bit()).
>
> Instead, we use clear_bit_unlock/test_and_set_bit_lock() here.
>
> Fixes: 0f4b1c7e89e6 ("rds: fix rds_send_xmit() serialization")
> Fixes: 1f9ecd7eacfd ("RDS: Pass rds_conn_path to rds_send_xmit()")
> Signed-off-by: Yewon Choi <woni9911@xxxxxxxxx>
> ---
> Changes in v1 -> v2:
> - Added missing Fixes tags
>
> net/rds/send.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/net/rds/send.c b/net/rds/send.c
> index 5e57a1581dc6..8f38009721b7 100644
> --- a/net/rds/send.c
> +++ b/net/rds/send.c
> @@ -103,13 +103,12 @@ EXPORT_SYMBOL_GPL(rds_send_path_reset);
>
> static int acquire_in_xmit(struct rds_conn_path *cp)
> {
> - return test_and_set_bit(RDS_IN_XMIT, &cp->cp_flags) == 0;
> + return test_and_set_bit_lock(RDS_IN_XMIT, &cp->cp_flags) == 0;
> }
>
> static void release_in_xmit(struct rds_conn_path *cp)
> {
> - clear_bit(RDS_IN_XMIT, &cp->cp_flags);
> - smp_mb__after_atomic();
> + clear_bit_unlock(RDS_IN_XMIT, &cp->cp_flags);
> /*
> * We don't use wait_on_bit()/wake_up_bit() because our waking is in a
> * hot path and finding waiters is very rare. We don't want to walk
> --
> 2.43.0
>
LGTM
Thanks,
Reviewed-by: Michal Kubiak <michal.kubiak@xxxxxxxxx>
