Hi,
On Tue, Jan 24, 2017 at 12:07:49PM +0800, Jeffy Chen wrote:
> It looks like bnep_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@xxxxxxxxxxxxxx>
> ---
>
> net/bluetooth/bnep/core.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c
> index fbf251f..da04d51 100644
> --- a/net/bluetooth/bnep/core.c
> +++ b/net/bluetooth/bnep/core.c
> @@ -484,16 +484,16 @@ static int bnep_session(void *arg)
> struct net_device *dev = s->dev;
> struct sock *sk = s->sock->sk;
> struct sk_buff *skb;
> - wait_queue_t wait;
> + DEFINE_WAIT_FUNC(wait, woken_wake_function);
>
> BT_DBG("");
>
> 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(&s->terminate))
> break;
> @@ -515,9 +515,8 @@ static int bnep_session(void *arg)
> break;
> netif_wake_queue(dev);
>
> - schedule();
> + wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
> }
> - __set_current_state(TASK_RUNNING);
> remove_wait_queue(sk_sleep(sk), &wait);
>
> /* Cleanup session */
> @@ -666,7 +665,11 @@ int bnep_del_connection(struct bnep_conndel_req *req)
> s = __bnep_get_session(req->dst);
> if (s) {
> atomic_inc(&s->terminate);
> - wake_up_process(s->task);
> +
> + /* Ensure session->terminate is updated */
> + smp_mb__after_atomic();
> +
__wake_up() suggests:
* It may be assumed that this function implies a write memory barrier before
* changing the task state if and only if any tasks are woken up.
so the above barrier is probably unnecessary. I'm not so sure about the
one before atomic_read(); seems fine.
Other than that, I this looks ok:
Reviewed-by: Brian Norris <briannorris@xxxxxxxxxxx>
But I haven't been testing BNEP.
Brian
> + wake_up_interruptible(sk_sleep(s->sock->sk));
> } else
> err = -ENOENT;
>
> --
> 2.1.4
>
>
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