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>
diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
index c405a95..43b4c2d 100644
--- a/net/bluetooth/hidp/core.c
+++ b/net/bluetooth/hidp/core.c
@@ -464,7 +464,8 @@
{
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 @@
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 @@
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 @@
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 @@
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 @@
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;