Bluetooth: cmtp: fix possible might sleep error in cmtp_session

It looks like cmtp_session has same pattern as the issue reported in
old rfcomm:

	while (1) {
		set_current_state(TASK_INTERRUPTIBLE);
		if (condition)
			break;
		// may call might_sleep here
		schedule();
	}
	__set_current_state(TASK_RUNNING);

Which fixed at:
	dfb2fae Bluetooth: Fix nested sleeps

So let's fix it at the same way, also follow the suggestion of:
https://lwn.net/Articles/628628/

Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: AL Yu-Chen Cho <acho@suse.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 10 insertions, 7 deletions

diff --git a/net/bluetooth/cmtp/core.c b/net/bluetooth/cmtp/core.c
index f4c64ef01c24..7f26a5a19ff6 100644
--- a/net/bluetooth/cmtp/core.c
+++ b/net/bluetooth/cmtp/core.c
@@ -280,16 +280,16 @@ static int cmtp_session(void *arg)
         struct cmtp_session *session = arg;
         struct sock *sk = session->sock->sk;
         struct sk_buff *skb;
-        wait_queue_t wait;
+        DEFINE_WAIT_FUNC(wait, woken_wake_function);
 
         BT_DBG("session %p", session);
 
         set_user_nice(current, -15);
 
-        init_waitqueue_entry(&wait, current);
         add_wait_queue(sk_sleep(sk), &wait);
         while (1) {
-                set_current_state(TASK_INTERRUPTIBLE);
+                /* Ensure session->terminate is updated */
+                smp_mb__before_atomic();
 
                 if (atomic_read(&session->terminate))
                         break;
@@ -306,9 +306,8 @@ static int cmtp_session(void *arg)
 
                 cmtp_process_transmit(session);
 
-                schedule();
+                wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
         }
-        __set_current_state(TASK_RUNNING);
         remove_wait_queue(sk_sleep(sk), &wait);
 
         down_write(&cmtp_session_sem);
@@ -393,7 +392,7 @@ int cmtp_add_connection(struct cmtp_connadd_req *req, struct socket *sock)
                 err = cmtp_attach_device(session);
                 if (err < 0) {
                         atomic_inc(&session->terminate);
-                        wake_up_process(session->task);
+                        wake_up_interruptible(sk_sleep(session->sock->sk));
                         up_write(&cmtp_session_sem);
                         return err;
                 }
@@ -431,7 +430,11 @@ int cmtp_del_connection(struct cmtp_conndel_req *req)
 
                 /* Stop session thread */
                 atomic_inc(&session->terminate);
-                wake_up_process(session->task);
+
+                /* Ensure session->terminate is updated */
+                smp_mb__after_atomic();
+
+                wake_up_interruptible(sk_sleep(session->sock->sk));
         } else
                 err = -ENOENT;