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Bluetooth: bnep: Fix deadlock in session deletion

PATCH Applied Peter Hurley 2 participants 2 messages Aug 5, 2011 – Aug 11, 2011

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Peter Hurley

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#0 lore raw

PATCH v2 1/1 Bluetooth: bnep: Fix deadlock in session deletion

Commit f4d7cd4a4c introduced the usage of kthread API. kthread_stop is a blocking function which returns only when the thread exits. In this case, the thread can't exit because it's waiting for the write lock, which is being held by bnep_del_connection() which is waiting for the thread to exit -- deadlock.

Use atomic_t/wake_up_process instead to signal to the thread to exit.

Signed-off-by Jaikumar Ganesh <[email protected]>
Signed-off-by Peter Hurley <[email protected]>
---
 net/bluetooth/bnep/bnep.h |    1 +
 net/bluetooth/bnep/core.c |    9 +++++----
 2 files changed, 6 insertions(+), 4 deletions(-)
net/bluetooth/bnep/bnep.h +1 -0
index 8e6c061..e7ee531 100644
@@ -155,6 +155,7 @@ struct bnep_session {
 	unsigned int  role;
 	unsigned long state;
 	unsigned long flags;
+	atomic_t      terminate;
 	struct task_struct *task;
 
 	struct ethhdr eh;
net/bluetooth/bnep/core.c +5 -4
index 7e8ff3c..d9edfe8 100644
@@ -487,7 +487,7 @@ static int bnep_session(void *arg)
 	while (1) {
 		set_current_state(TASK_INTERRUPTIBLE);
 
-		if (kthread_should_stop())
+		if (atomic_read(&s->terminate))
 			break;
 		/* RX */
 		while ((skb = skb_dequeue(&sk->sk_receive_queue))) {

@@ -642,9 +642,10 @@ int bnep_del_connection(struct bnep_conndel_req *req)
 	down_read(&bnep_session_sem);
 
 	s = __bnep_get_session(req->dst);
-	if (s)
-		kthread_stop(s->task);
-	else
+	if (s) {
+		atomic_inc(&s->terminate);
+		wake_up_process(s->task);
+	} else
 		err = -ENOENT;
 
 	up_read(&bnep_session_sem);
Signature · 1 line
1.7.4.1
Applied
#1 lore raw

Hi Peter,

Quoted 6 lines · Peter Hurley

Commit f4d7cd4a4c introduced the usage of kthread API. kthread_stop is a blocking function which returns only when the thread exits. In this case, the thread can't exit because it's waiting for the write lock, which is being held by bnep_del_connection() which is waiting for the thread to exit -- deadlock.

Quoted 8 lines

Use atomic_t/wake_up_process instead to signal to the thread to exit.

Signed-off-by Jaikumar Ganesh <[email protected]>
Signed-off-by Peter Hurley <[email protected]>
---
 net/bluetooth/bnep/bnep.h |    1 +
 net/bluetooth/bnep/core.c |    9 +++++----
 2 files changed, 6 insertions(+), 4 deletions(-)

Applied, thanks.

Gustavo