linux-kernel - [PATCH 4.19 116/140] net/smc: do not wait under send

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Message-Id: <20191216174819.039049758@linuxfoundation.org>
Date:   Mon, 16 Dec 2019 18:49:44 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Karsten Graul <kgraul@...ux.ibm.com>,
        Ursula Braun <ubraun@...ux.ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 116/140] net/smc: do not wait under send_lock

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

[ Upstream commit 33f3fcc290671590821ff3c0c9396db1ec9b7d4c ]

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>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 0ecbbdc337b82..62885a2781c9a 100644
--- a/net/smc/smc_tx.c
+++ b/net/smc/smc_tx.c
@@ -486,25 +486,23 @@ 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) {
-- 
2.20.1