Hi Dmitry, On 02/14/2017 05:27 AM, Dmitry Torokhov wrote:
Hi Jeffy, On Sun, Feb 12, 2017 at 8:12 PM, Jeffy Chen <jeffy.chen@xxxxxxxxxxxxxx> wrote:It looks like hidp_session_thread 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> 1/ Fix could not wake up by wake attempts on original wait queues. 2/ Remove unnecessary memory barrier before wake_up_* functions. --- Changes in v3: None Changes in v2: None net/bluetooth/hidp/core.c | 33 ++++++++++++++++++++++----------- 1 file changed, 22 insertions(+), 11 deletions(-) diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c index 0bec458..076bc50 100644 --- a/net/bluetooth/hidp/core.c +++ b/net/bluetooth/hidp/core.c @@ -36,6 +36,7 @@ #define VERSION "1.2" static DECLARE_RWSEM(hidp_session_sem); +static DECLARE_WAIT_QUEUE_HEAD(hidp_session_wq); static LIST_HEAD(hidp_session_list); static unsigned char hidp_keycode[256] = { @@ -1068,12 +1069,12 @@ static int hidp_session_start_sync(struct hidp_session *session) * Wake up session thread and notify it to stop. This is asynchronous and * returns immediately. Call this whenever a runtime error occurs and you want * the session to stop. - * Note: wake_up_process() performs any necessary memory-barriers for us. + * Note: wake_up_interruptible() performs any necessary memory-barriers for us. */ static void hidp_session_terminate(struct hidp_session *session) { atomic_inc(&session->terminate); - wake_up_process(session->task); + wake_up_interruptible(&hidp_session_wq); } /* @@ -1180,7 +1181,9 @@ 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(&hidp_session_wq, &wait); for (;;) { /* * This thread can be woken up two ways: @@ -1188,12 +1191,10 @@ 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 +1228,22 @@ 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); } + remove_wait_queue(&hidp_session_wq, &wait); atomic_inc(&session->terminate); - set_current_state(TASK_RUNNING); + + /* Ensure session->terminate is updated */ + smp_mb__after_atomic(); +} + +int hidp_session_wake_function(wait_queue_t *wait, unsigned int mode, + int sync, void *key)static?
Oops, sure.
+{ + wake_up_interruptible(&hidp_session_wq); + + return default_wake_function(wait, mode, sync, key);I do not think you need to call default_wake_function() here: the process is waiting on hidp_session_wq, so the wakeup above is what will wake up the session. By the time you get to call default_wake_function() task will already be in wrong state. I think we should simply return "false" instead of calling default_wake_function().
Ok, thanx.
} /* @@ -1244,7 +1256,8 @@ static void hidp_session_run(struct hidp_session *session) static int hidp_session_thread(void *arg) { struct hidp_session *session = arg; - wait_queue_t ctrl_wait, intr_wait; + DEFINE_WAIT_FUNC(ctrl_wait, hidp_session_wake_function); + DEFINE_WAIT_FUNC(intr_wait, hidp_session_wake_function); BT_DBG("session %p", session); @@ -1254,8 +1267,6 @@ static int hidp_session_thread(void *arg) set_user_nice(current, -15); hidp_set_timer(session); - init_waitqueue_entry(&ctrl_wait, current); - init_waitqueue_entry(&intr_wait, current); add_wait_queue(sk_sleep(session->ctrl_sock->sk), &ctrl_wait); add_wait_queue(sk_sleep(session->intr_sock->sk), &intr_wait); /* This memory barrier is paired with wq_has_sleeper(). See -- 2.1.4Thanks.
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