On 1/30/22 19:02, Tony Lu wrote:
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>
---
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 ffab9cee747d..ef021ec6b361 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -2600,8 +2600,8 @@ 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)
Could you add a comment that we're expecting lock_sock() to be held when calling
this function?
Thanks,
Stefan
