[tipc-discussion][net 2/2] tipc: improve function tipc_wait_for_rcvmsg()

[Tung Nguyen]

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....@windriver.com>
Acked-by: Jon Maloy <jon.ma...@ericsson.com>
Signed-off-by: Tung Nguyen <tung.q.ngu...@dektech.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