@@ -1633,7 +1633,9 @@ static inline int l2cap_skbuff_fromiovec(struct sock *sk, struct msghdr *msg, in
while (len) {
count = min_t(unsigned int, conn->mtu, len);
+ release_sock(sk);
*frag = bt_skb_send_alloc(sk, count, msg->msg_flags & MSG_DONTWAIT, &err);
+ lock_sock(sk);
if (!*frag)
return -EFAULT;
if (memcpy_fromiovec(skb_put(*frag, count), msg->msg_iov, count))
@@ -1724,8 +1726,10 @@ static struct sk_buff *l2cap_create_iframe_pdu(struct sock *sk, struct msghdr *m
hlen += 2;
count = min_t(unsigned int, (conn->mtu - hlen), len);
+ release_sock(sk);
skb = bt_skb_send_alloc(sk, count + hlen,
msg->msg_flags & MSG_DONTWAIT, &err);
+ lock_sock(sk);
if (!skb)
return ERR_PTR(-ENOMEM);
The Enhanced Retransmission Mode(ERTM) is a realiable mode of operation of the Bluetooth L2CAP layer. Think on it like a simplified version of TCP. The problem we were facing here was a deadlock. ERTM uses a backlog queue to queue incomimg packets while the user is helding the lock. The problem is that at some moment the user doesn't have memory anymore to do alloc new skbs and sleep with the lock to wait for memory, that stalls the ERTM connection once we can't read the acknowledgements packets in the backlog queue to free memory and make the allocation of outcoming skb successful. I'm thinking on this patch more like a proof of concept than a real fix to the deadlock in ERTM. Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi> --- net/bluetooth/l2cap.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-)