Messages in this thread | | | Date | Tue, 14 Feb 2017 08:57:50 +0800 | From | jeffy <> | Subject | Re: [PATCH v3 3/3] Bluetooth: hidp: fix possible might sleep error in hidp_session_thread |
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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@rock-chips.com> 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@rock-chips.com> >> 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 >> -- >> 2.1.4 >> >> > Thanks. >
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