Re: [PATCH v4 2/3] Bluetooth: cmtp: fix possible might sleep error in cmtp_session

AL Yu-Chen Cho
2017-06-12T08:44:18Z

> 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>
> Remove unnecessary memory barrier before wake_up_* functions.
Reviewed-by: AL Yu-Chen Cho <acho@suse.com>
>
> ---
>
> Changes in v3:
> Add brian's Reviewed-by.
>
> Changes in v2: None
>
> net/bluetooth/cmtp/core.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/net/bluetooth/cmtp/core.c b/net/bluetooth/cmtp/core.c
> index 9e59b66..1152ce3 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;
>