2014-10-29 08:16:00

by Jukka Rissanen

Subject: [PATCH v4] Bluetooth: Wrong style spin lock used

Use spin_lock_bh() as the code is called from softirq in networking subsystem.
This is needed to prevent deadlocks when 6lowpan link is in use.

Signed-off-by: Jukka Rissanen <[email protected]>
---
Hi,

this v4 adds a comment why spin_lock_bh() is needed here.

Cheers,
Jukka

net/bluetooth/hci_core.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index cb05d7f..2397623 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -4661,8 +4661,12 @@ static void hci_queue_acl(struct hci_chan *chan, struct sk_buff_head *queue,

skb_shinfo(skb)->frag_list = NULL;

- /* Queue all fragments atomically */
- spin_lock(&queue->lock);
+ /* Queue all fragments atomically. We need to use spin_lock_bh
+ * here because of 6LoWPAN links, as there this function is
+ * called from softirq and using normal spin lock could cause
+ * deadlocks.
+ */
+ spin_lock_bh(&queue->lock);

__skb_queue_tail(queue, skb);

@@ -4679,7 +4683,7 @@ static void hci_queue_acl(struct hci_chan *chan, struct sk_buff_head *queue,
__skb_queue_tail(queue, skb);
} while (list);

- spin_unlock(&queue->lock);
+ spin_unlock_bh(&queue->lock);
}
}

--
1.8.3.1

2014-10-29 15:23:10

by Marcel Holtmann

Subject: Re: [PATCH v4] Bluetooth: Wrong style spin lock used

Hi Jukka,

> Use spin_lock_bh() as the code is called from softirq in networking subsystem.
> This is needed to prevent deadlocks when 6lowpan link is in use.
>
> Signed-off-by: Jukka Rissanen <[email protected]>
> ---
> Hi,
>
> this v4 adds a comment why spin_lock_bh() is needed here.
>
> Cheers,
> Jukka
>
> net/bluetooth/hci_core.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)

patch has been applied to bluetooth-next tree.

Regards

Marcel