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Commit 7bb59df8 authored by Peter Hurley's avatar Peter Hurley Committed by Gustavo Padovan
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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: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGustavo F. Padovan <padovan@profusion.mobi>
parent 7ac28817

net/bluetooth/hidp/core.c

+11 −7
Original line number Diff line number Diff line
@@ -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);



	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;

net/bluetooth/hidp/hidp.h

+1 −0
Original line number Diff line number Diff line
@@ -142,6 +142,7 @@ struct hidp_session { 
	uint ctrl_mtu;

	uint intr_mtu;



	atomic_t terminate;

	struct task_struct *task;



	unsigned char keys[8];