[PATCH 4.19 116/140] net/smc: do not wait under send_lock

Greg Kroah-Hartman
2019-12-16T18:37:44Z

From: Karsten Graul <kgraul@linux.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@linux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.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