From 7bb59df83b190817f56c4e2fec3078d99d906ad4 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Thu, 30 Jun 2011 13:53:53 -0400 Subject: [PATCH] Bluetooth: Fix hidp disconnect deadlocks and lost wakeup Partial revert of commit aabf6f89. When the hidp session thread was converted from kernel_thread to kthread, the atomic/wakeups were replaced with kthread_stop. kthread_stop has blocking semantics which are inappropriate for the hidp session kthread. In addition, the kthread signals itself to terminate in hidp_process_hid_control() - it cannot do this with kthread_stop(). Lastly, a wakeup can be lost if the wakeup happens between checking for the loop exit condition and setting the current state to TASK_INTERRUPTIBLE. (Without appropriate synchronization mechanisms, the task state should not be changed between the condition test and the yield - via schedule() - as this creates a race between the wakeup and resetting the state back to interruptible.) Signed-off-by: Peter Hurley Signed-off-by: Gustavo F. Padovan --- net/bluetooth/hidp/core.c | 18 +++++++++++------- net/bluetooth/hidp/hidp.h | 1 + 2 files changed, 12 insertions(+), 7 deletions(-) diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c index c405a954a603..43b4c2deb7cc 100644 --- a/net/bluetooth/hidp/core.c +++ b/net/bluetooth/hidp/core.c @@ -464,7 +464,8 @@ static void hidp_idle_timeout(unsigned long arg) { struct hidp_session *session = (struct hidp_session *) arg; - kthread_stop(session->task); + atomic_inc(&session->terminate); + wake_up_process(session->task); } static void hidp_set_timer(struct hidp_session *session) @@ -535,7 +536,8 @@ static void hidp_process_hid_control(struct hidp_session *session, skb_queue_purge(&session->ctrl_transmit); skb_queue_purge(&session->intr_transmit); - kthread_stop(session->task); + atomic_inc(&session->terminate); + wake_up_process(current); } } @@ -706,9 +708,8 @@ static int hidp_session(void *arg) add_wait_queue(sk_sleep(intr_sk), &intr_wait); session->waiting_for_startup = 0; wake_up_interruptible(&session->startup_queue); - while (!kthread_should_stop()) { - set_current_state(TASK_INTERRUPTIBLE); - + set_current_state(TASK_INTERRUPTIBLE); + while (!atomic_read(&session->terminate)) { if (ctrl_sk->sk_state != BT_CONNECTED || intr_sk->sk_state != BT_CONNECTED) break; @@ -726,6 +727,7 @@ static int hidp_session(void *arg) hidp_process_transmit(session); schedule(); + set_current_state(TASK_INTERRUPTIBLE); } set_current_state(TASK_RUNNING); remove_wait_queue(sk_sleep(intr_sk), &intr_wait); @@ -1060,7 +1062,8 @@ int hidp_add_connection(struct hidp_connadd_req *req, struct socket *ctrl_sock, err_add_device: hid_destroy_device(session->hid); session->hid = NULL; - kthread_stop(session->task); + atomic_inc(&session->terminate); + wake_up_process(session->task); unlink: hidp_del_timer(session); @@ -1111,7 +1114,8 @@ int hidp_del_connection(struct hidp_conndel_req *req) skb_queue_purge(&session->ctrl_transmit); skb_queue_purge(&session->intr_transmit); - kthread_stop(session->task); + atomic_inc(&session->terminate); + wake_up_process(session->task); } } else err = -ENOENT; diff --git a/net/bluetooth/hidp/hidp.h b/net/bluetooth/hidp/hidp.h index 19e95004b286..af1bcc823f26 100644 --- a/net/bluetooth/hidp/hidp.h +++ b/net/bluetooth/hidp/hidp.h @@ -142,6 +142,7 @@ struct hidp_session { uint ctrl_mtu; uint intr_mtu; + atomic_t terminate; struct task_struct *task; unsigned char keys[8]; -- 2.20.1