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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: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
This commit is contained in:
Peter Hurley 2011-06-30 13:53:53 -04:00 committed by Gustavo F. Padovan
parent 7ac2881753
commit 7bb59df83b
2 changed files with 12 additions and 7 deletions
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18
net/bluetooth/hidp/core.c
View File

@ -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;

1
net/bluetooth/hidp/hidp.h
View File

@ -142,6 +142,7 @@ struct hidp_session {
uint ctrl_mtu;
uint intr_mtu;
atomic_t terminate;
struct task_struct *task;
unsigned char keys[8];