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Bluetooth: Fix hidp disconnect deadlocks and lost wakeup

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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
Download Patch File Download Diff File Expand all files Collapse all files

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; 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) 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->ctrl_transmit);
skb_queue_purge(&session->intr_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); add_wait_queue(sk_sleep(intr_sk), &intr_wait);
session->waiting_for_startup = 0; session->waiting_for_startup = 0;
wake_up_interruptible(&session->startup_queue); 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 || if (ctrl_sk->sk_state != BT_CONNECTED ||
intr_sk->sk_state != BT_CONNECTED) intr_sk->sk_state != BT_CONNECTED)
break; break;
@@ -726,6 +727,7 @@ static int hidp_session(void *arg)
hidp_process_transmit(session); hidp_process_transmit(session);
schedule(); schedule();
set_current_state(TASK_INTERRUPTIBLE);
} }
set_current_state(TASK_RUNNING); set_current_state(TASK_RUNNING);
remove_wait_queue(sk_sleep(intr_sk), &intr_wait); 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: err_add_device:
hid_destroy_device(session->hid); hid_destroy_device(session->hid);
session->hid = NULL; session->hid = NULL;
kthread_stop(session->task); atomic_inc(&session->terminate);
wake_up_process(session->task);
unlink: unlink:
hidp_del_timer(session); 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->ctrl_transmit);
skb_queue_purge(&session->intr_transmit); skb_queue_purge(&session->intr_transmit);
kthread_stop(session->task); atomic_inc(&session->terminate);
wake_up_process(session->task);
} }
} else } else
err = -ENOENT; err = -ENOENT;

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

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