linux-kernel - Re: [PATCH net] rds: Fix non-atomic operation on shared flag variable

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Message-ID: <6a4e095f-20f1-53af-a2eb-047866c1695d@oracle.com>
Date:   Tue, 5 Sep 2017 09:33:04 -0700
From:   Santosh Shilimkar <santosh.shilimkar@...cle.com>
To:     Håkon Bugge <Haakon.Bugge@...cle.com>
Cc:     "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, rds-devel@....oracle.com,
        linux-kernel@...r.kernel.org, knut.omang@...cle.com,
        wei.lin.guay@...cle.com
Subject: Re: [PATCH net] rds: Fix non-atomic operation on shared flag variable

On 9/5/2017 8:42 AM, Håkon Bugge wrote:
> The bits in m_flags in struct rds_message are used for a plurality of
> reasons, and from different contexts. To avoid any missing updates to
> m_flags, use the atomic set_bit() instead of the non-atomic equivalent.
> 
> Signed-off-by: Håkon Bugge <haakon.bugge@...cle.com>
> Reviewed-by: Knut Omang <knut.omang@...cle.com>
> Reviewed-by: Wei Lin Guay <wei.lin.guay@...cle.com>
> ---
>   net/rds/send.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/rds/send.c b/net/rds/send.c
> index 41b9f0f..058a407 100644
> --- a/net/rds/send.c
> +++ b/net/rds/send.c
> @@ -273,7 +273,7 @@ int rds_send_xmit(struct rds_conn_path *cp)
>   			len = ntohl(rm->m_inc.i_hdr.h_len);
>   			if (cp->cp_unacked_packets == 0 ||
>   			    cp->cp_unacked_bytes < len) {
> -				__set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
> +				set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
>   
>   				cp->cp_unacked_packets =
>   					rds_sysctl_max_unacked_packets;
> @@ -829,7 +829,7 @@ static int rds_send_queue_rm(struct rds_sock *rs, struct rds_connection *conn,
>   		 * throughput hits a certain threshold.
>   		 */
>   		if (rs->rs_snd_bytes >= rds_sk_sndbuf(rs) / 2)
> -			__set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
> +			set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
>   
>   		list_add_tail(&rm->m_sock_item, &rs->rs_send_queue);
>   		set_bit(RDS_MSG_ON_SOCK, &rm->m_flags);
> 
Indeed, these couple of instances remained for the m_flags.
Patch looks good. Thanks !!

Acked-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>