Hi Jeffy, On Fri, Jan 20, 2017 at 09:52:08PM +0800, Jeffy Chen wrote: > [ 39.044329] do not call blocking ops when !TASK_RUNNING; state=1 set > at [<ffffffbffc290358>] hidp_session_thread+0x110/0x568 [hidp] > ... > [ 40.159664] Call trace: > [ 40.162122] [<ffffffc00024ae08>] __might_sleep+0x64/0x90 > [ 40.167443] [<ffffffc00080568c>] lock_sock_nested+0x30/0x78 > [ 40.173047] [<ffffffbffc1b3ca0>] l2cap_sock_sendmsg+0x90/0xf0 > [bluetooth] > [ 40.179842] [<ffffffc0008012c4>] sock_sendmsg+0x4c/0x68 > [ 40.185072] [<ffffffc000801414>] kernel_sendmsg+0x54/0x68 > [ 40.190477] [<ffffffbffc28f4d0>] hidp_send_frame+0x78/0xa0 [hidp] > [ 40.196574] [<ffffffbffc28f53c>] hidp_process_transmit+0x44/0x98 > [hidp] > [ 40.203191] [<ffffffbffc2905ac>] hidp_session_thread+0x364/0x568 > [hidp] Am I crazy, or are several other protocols broken like this too? I see a similar structure in net/bluetooth/bnep/core.c and net/bluetooth/cmtp/core.c, at least, each of which also call kernel_sendmsg(), which might be an l2cap socket (...I think? I'm not a bluetooth expert really). > > Following (https://lwn.net/Articles/628628/). > > Signed-off-by: Jeffy Chen <jeffy.chen@xxxxxxxxxxxxxx> > --- > > net/bluetooth/hidp/core.c | 15 +++++++++------ > 1 file changed, 9 insertions(+), 6 deletions(-) > > diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c > index 0bec458..bfd3fb8 100644 > --- a/net/bluetooth/hidp/core.c > +++ b/net/bluetooth/hidp/core.c > @@ -1180,7 +1180,9 @@ static void hidp_session_run(struct hidp_session *session) > struct sock *ctrl_sk = session->ctrl_sock->sk; > struct sock *intr_sk = session->intr_sock->sk; > struct sk_buff *skb; > + DEFINE_WAIT_FUNC(wait, woken_wake_function); > > + add_wait_queue(sk_sleep(intr_sk), &wait); > for (;;) { > /* > * This thread can be woken up two ways: > @@ -1188,12 +1190,10 @@ static void hidp_session_run(struct hidp_session *session) > * session->terminate flag and wakes this thread up. > * - Via modifying the socket state of ctrl/intr_sock. This > * thread is woken up by ->sk_state_changed(). > - * > - * Note: set_current_state() performs any necessary > - * memory-barriers for us. > */ > - set_current_state(TASK_INTERRUPTIBLE); > > + /* Ensure session->terminate is updated */ > + smp_mb__before_atomic(); > if (atomic_read(&session->terminate)) > break; > > @@ -1227,11 +1227,14 @@ static void hidp_session_run(struct hidp_session *session) > hidp_process_transmit(session, &session->ctrl_transmit, > session->ctrl_sock); > > - schedule(); > + wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); I think this looks mostly good, except what about the hidp_session_terminate() condition? In that case, you're running wake_up_process() -- which won't set WQ_FLAG_WOKEN for us. So what happens if we see a hidp_session_terminate() call in between the check for the ->terminate count, but before we call wait_woken()? IIUC, I think we'll just ignore the call and keep waiting for the next wake signal. I think you might need to rework hidp_session_terminate() too, to actually target the wait queue and not just the processes. IIUC, of course. I could be wrong... Brian > } > + remove_wait_queue(sk_sleep(intr_sk), &wait); > > atomic_inc(&session->terminate); > - set_current_state(TASK_RUNNING); > + > + /* Ensure session->terminate is updated */ > + smp_mb__after_atomic(); > } > > /* > -- > 2.1.4 > > -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
