From: Tony Lu <tonylu@xxxxxxxxxxxxxxxxx> [ Upstream commit ea785a1a573b390a150010b3c5b81e1ccd8c98a8 ] According to the man page of TCP_CORK [1], if set, don't send out partial frames. All queued partial frames are sent when option is cleared again. When applications call setsockopt to disable TCP_CORK, this call is protected by lock_sock(), and tries to mod_delayed_work() to 0, in order to send pending data right now. However, the delayed work smc_tx_work is also protected by lock_sock(). There introduces lock contention for sending data. To fix it, send pending data directly which acts like TCP, without lock_sock() protected in the context of setsockopt (already lock_sock()ed), and cancel unnecessary dealyed work, which is protected by lock. [1] https://linux.die.net/man/7/tcp Signed-off-by: Tony Lu <tonylu@xxxxxxxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- net/smc/af_smc.c | 4 ++-- net/smc/smc_tx.c | 25 +++++++++++++++---------- net/smc/smc_tx.h | 1 + 3 files changed, 18 insertions(+), 12 deletions(-) diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index a0fb596459a3..0ec721b8059a 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -2632,8 +2632,8 @@ static int smc_setsockopt(struct socket *sock, int level, int optname, sk->sk_state != SMC_CLOSED) { if (!val) { SMC_STAT_INC(smc, cork_cnt); - mod_delayed_work(smc->conn.lgr->tx_wq, - &smc->conn.tx_work, 0); + smc_tx_pending(&smc->conn); + cancel_delayed_work(&smc->conn.tx_work); } } break; diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c index be241d53020f..7b0b6e24582f 100644 --- a/net/smc/smc_tx.c +++ b/net/smc/smc_tx.c @@ -597,27 +597,32 @@ int smc_tx_sndbuf_nonempty(struct smc_connection *conn) return rc; } -/* Wakeup sndbuf consumers from process context - * since there is more data to transmit - */ -void smc_tx_work(struct work_struct *work) +void smc_tx_pending(struct smc_connection *conn) { - struct smc_connection *conn = container_of(to_delayed_work(work), - struct smc_connection, - tx_work); struct smc_sock *smc = container_of(conn, struct smc_sock, conn); int rc; - lock_sock(&smc->sk); if (smc->sk.sk_err) - goto out; + return; rc = smc_tx_sndbuf_nonempty(conn); if (!rc && conn->local_rx_ctrl.prod_flags.write_blocked && !atomic_read(&conn->bytes_to_rcv)) conn->local_rx_ctrl.prod_flags.write_blocked = 0; +} + +/* Wakeup sndbuf consumers from process context + * since there is more data to transmit + */ +void smc_tx_work(struct work_struct *work) +{ + struct smc_connection *conn = container_of(to_delayed_work(work), + struct smc_connection, + tx_work); + struct smc_sock *smc = container_of(conn, struct smc_sock, conn); -out: + lock_sock(&smc->sk); + smc_tx_pending(conn); release_sock(&smc->sk); } diff --git a/net/smc/smc_tx.h b/net/smc/smc_tx.h index 07e6ad76224a..a59f370b8b43 100644 --- a/net/smc/smc_tx.h +++ b/net/smc/smc_tx.h @@ -27,6 +27,7 @@ static inline int smc_tx_prepared_sends(struct smc_connection *conn) return smc_curs_diff(conn->sndbuf_desc->len, &sent, &prep); } +void smc_tx_pending(struct smc_connection *conn); void smc_tx_work(struct work_struct *work); void smc_tx_init(struct smc_sock *smc); int smc_tx_sendmsg(struct smc_sock *smc, struct msghdr *msg, size_t len); -- 2.34.1
