The recent poll change may lead to stalls for non-blocking connecting
SMC sockets, since sock_poll_wait is no longer performed on the
internal CLC socket, but on the outer SMC socket. kernel_connect() on
the internal CLC socket returns with -EINPROGRESS, but the wake up
logic does not work in all cases. If the internal CLC socket is still
in state TCP_SYN_SENT when polled, sock_poll_wait() from sock_poll()
does not sleep. It is supposed to sleep till the state of the internal
CLC socket switches to TCP_ESTABLISHED.
This patch temporarily propagates the wait queue from the internal
CLC sock to the SMC sock, till the non-blocking connect() is
finished.
In addition locking is reduced due to the removed poll waits.
Fixes: c0129a061442 ("smc: convert to ->poll_mask")
Signed-off-by: Ursula Braun <ubr...@linux.ibm.com>
---
net/smc/af_smc.c | 15 +++++++++++----
net/smc/smc.h | 1 +
2 files changed, 12 insertions(+), 4 deletions(-)
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index da7f02edcd37..d76331aae6e1 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -23,6 +23,7 @@
#include <linux/workqueue.h>
#include <linux/in.h>
#include <linux/sched/signal.h>
+#include <linux/rcupdate.h>
#include <net/sock.h>
#include <net/tcp.h>
@@ -605,6 +606,13 @@ static int smc_connect(struct socket *sock, struct
sockaddr *addr,
smc_copy_sock_settings_to_clc(smc);
tcp_sk(smc->clcsock->sk)->syn_smc = 1;
+ if (flags & O_NONBLOCK) {
+ rcu_read_lock();
+ smc->smcwq = rcu_dereference(sk->sk_wq);
+ rcu_assign_pointer(sock->sk->sk_wq,
+ rcu_dereference(smc->clcsock->sk->sk_wq));
+ rcu_read_unlock();
+ }
rc = kernel_connect(smc->clcsock, addr, alen, flags);
if (rc)
goto out;
@@ -1285,12 +1293,9 @@ static __poll_t smc_poll_mask(struct socket *sock,
__poll_t events)
smc = smc_sk(sock->sk);
sock_hold(sk);
- lock_sock(sk);
if ((sk->sk_state == SMC_INIT) || smc->use_fallback) {
/* delegate to CLC child sock */
- release_sock(sk);
mask = smc->clcsock->ops->poll_mask(smc->clcsock, events);
- lock_sock(sk);
sk->sk_err = smc->clcsock->sk->sk_err;
if (sk->sk_err) {
mask |= EPOLLERR;
@@ -1299,7 +1304,10 @@ static __poll_t smc_poll_mask(struct socket *sock,
__poll_t events)
if (sk->sk_state == SMC_INIT &&
mask & EPOLLOUT &&
smc->clcsock->sk->sk_state != TCP_CLOSE) {
+ lock_sock(sk);
+ rcu_assign_pointer(sock->sk->sk_wq, smc->smcwq);
rc = __smc_connect(smc);
+ release_sock(sk);
if (rc < 0)
mask |= EPOLLERR;
/* success cases including fallback */
@@ -1334,7 +1342,6 @@ static __poll_t smc_poll_mask(struct socket *sock,
__poll_t events)
mask |= EPOLLPRI;
}
- release_sock(sk);
sock_put(sk);
return mask;
diff --git a/net/smc/smc.h b/net/smc/smc.h
index 51ae1f10d81a..89d6d7ef973f 100644
--- a/net/smc/smc.h
+++ b/net/smc/smc.h
@@ -190,6 +190,7 @@ struct smc_connection {
struct smc_sock { /* smc sock container */
struct sock sk;
struct socket *clcsock; /* internal tcp socket */
+ struct socket_wq *smcwq; /* original smcsock wq */
struct smc_connection conn; /* smc connection */
struct smc_sock *listen_smc; /* listen parent */
struct work_struct tcp_listen_work;/* handle tcp socket accepts */
--
2.16.4
