Hi Gustavo -
On Thu, 31 May 2012, Gustavo Padovan wrote:
From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
To avoid deadlock we need to release locks while waiting for a ack to
arrive.
Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
---
net/bluetooth/l2cap_core.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 1cb3ca0..94273dc 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -1553,13 +1553,14 @@ done:
int __l2cap_wait_ack(struct sock *sk)
{
struct l2cap_chan *chan = l2cap_pi(sk)->chan;
+ struct l2cap_conn *conn = chan->conn;
I don't think you want to store the l2cap_conn pointer on the stack,
the structure can be freed when the locks are released.
DECLARE_WAITQUEUE(wait, current);
int err = 0;
int timeo = HZ/5;
add_wait_queue(sk_sleep(sk), &wait);
set_current_state(TASK_INTERRUPTIBLE);
- while (chan->unacked_frames > 0 && chan->conn) {
+ while (chan->unacked_frames > 0 && conn) {
if (!timeo)
timeo = HZ/5;
@@ -1570,7 +1571,9 @@ int __l2cap_wait_ack(struct sock *sk)
release_sock(sk);
l2cap_chan_unlock(chan);
+ mutex_unlock(&conn->chan_lock);
timeo = schedule_timeout(timeo);
+ mutex_lock(&conn->chan_lock);
l2cap_chan_lock(chan);
lock_sock(sk);
set_current_state(TASK_INTERRUPTIBLE);
--
1.7.10.2
I think it would be better to only acquire the chan_lock mutex when
calling l2cap_chan_close in l2cap_sock_shutdown. However, you will
have to be careful to avoid deadlocks. I think it's only safe to
acquire the conn->chan_lock when both the l2cap_chan and the socket
are unlocked. Can you collapse all the locking changes in to one
patch?
Since __l2cap_wait_ack is only called from l2cap_sock.c, would it
make sense to move the function to l2cap_sock.c?
--
Mat Martineau
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum
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