netdev - [PATCH net 6/9] net/smc: do not wait under send

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Date:   Wed, 30 Jan 2019 18:51:05 +0100
From:   Ursula Braun <ubraun@...ux.ibm.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        raspl@...ux.ibm.com, ubraun@...ux.ibm.com
Subject: [PATCH net 6/9] net/smc: do not wait under send_lock

From: Karsten Graul <kgraul@...ux.ibm.com>

smc_cdc_get_free_slot() might wait for free transfer buffers when using
SMC-R. This wait should not be done under the send_lock, which is a
spin_lock. This fixes a cpu loop in parallel threads waiting for the
send_lock.

Signed-off-by: Karsten Graul <kgraul@...ux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@...ux.ibm.com>
---
 net/smc/smc_tx.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c
index f99951f3f7fd..36af3de731b9 100644
--- a/net/smc/smc_tx.c
+++ b/net/smc/smc_tx.c
@@ -488,25 +488,23 @@ static int smcr_tx_sndbuf_nonempty(struct smc_connection *conn)
 	struct smc_wr_buf *wr_buf;
 	int rc;
 
-	spin_lock_bh(&conn->send_lock);
 	rc = smc_cdc_get_free_slot(conn, &wr_buf, &pend);
 	if (rc < 0) {
 		if (rc == -EBUSY) {
 			struct smc_sock *smc =
 				container_of(conn, struct smc_sock, conn);
 
-			if (smc->sk.sk_err == ECONNABORTED) {
-				rc = sock_error(&smc->sk);
-				goto out_unlock;
-			}
+			if (smc->sk.sk_err == ECONNABORTED)
+				return sock_error(&smc->sk);
 			rc = 0;
 			if (conn->alert_token_local) /* connection healthy */
 				mod_delayed_work(system_wq, &conn->tx_work,
 						 SMC_TX_WORK_DELAY);
 		}
-		goto out_unlock;
+		return rc;
 	}
 
+	spin_lock_bh(&conn->send_lock);
 	if (!conn->local_tx_ctrl.prod_flags.urg_data_present) {
 		rc = smc_tx_rdma_writes(conn);
 		if (rc) {
-- 
2.16.4