netdev - [tipc-discussion][net 2/2] tipc: improve function tipc_wait_for

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Date:   Tue, 19 Feb 2019 11:20:48 +0700
From:   Tung Nguyen <tung.q.nguyen@...tech.com.au>
To:     davem@...emloft.net, netdev@...r.kernel.org
Cc:     tipc-discussion@...ts.sourceforge.net
Subject: [tipc-discussion][net 2/2] tipc: improve function tipc_wait_for_rcvmsg()

This commit replaces schedule_timeout() with wait_woken()
in function tipc_wait_for_rcvmsg(). wait_woken() uses
memory barriers in its implementation to avoid potential
race condition when putting a process into sleeping state
and then waking it up.

Acked-by: Ying Xue <ying.xue@...driver.com>
Acked-by: Jon Maloy <jon.maloy@...csson.com>
Signed-off-by: Tung Nguyen <tung.q.nguyen@...tech.com.au>
---
 net/tipc/socket.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 81b87916a0eb..684f2125fc6b 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -1677,7 +1677,7 @@ static void tipc_sk_send_ack(struct tipc_sock *tsk)
 static int tipc_wait_for_rcvmsg(struct socket *sock, long *timeop)
 {
 	struct sock *sk = sock->sk;
-	DEFINE_WAIT(wait);
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
 	long timeo = *timeop;
 	int err = sock_error(sk);
 
@@ -1685,15 +1685,17 @@ static int tipc_wait_for_rcvmsg(struct socket *sock, long *timeop)
 		return err;
 
 	for (;;) {
-		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
 		if (timeo && skb_queue_empty(&sk->sk_receive_queue)) {
 			if (sk->sk_shutdown & RCV_SHUTDOWN) {
 				err = -ENOTCONN;
 				break;
 			}
+			add_wait_queue(sk_sleep(sk), &wait);
 			release_sock(sk);
-			timeo = schedule_timeout(timeo);
+			timeo = wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
+			sched_annotate_sleep();
 			lock_sock(sk);
+			remove_wait_queue(sk_sleep(sk), &wait);
 		}
 		err = 0;
 		if (!skb_queue_empty(&sk->sk_receive_queue))
@@ -1709,7 +1711,6 @@ static int tipc_wait_for_rcvmsg(struct socket *sock, long *timeop)
 		if (err)
 			break;
 	}
-	finish_wait(sk_sleep(sk), &wait);
 	*timeop = timeo;
 	return err;
 }
-- 
2.17.1