Re: [PATCH] Bluetooth: Use non locking get_chan and explicit lock

[Marcel Holtmann <marcel@holtmann.org>]

Hi Andrei,

> For receiving ACL packets use __l2cap_get_chan_by_scid which is not
> locking sk and explicitly lock sk after checking that it is exist.
> Code looks nicer since now it is surrounded by lock/release.
> 
> Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
> ---
>  net/bluetooth/l2cap_core.c |    7 +++++--
>  1 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> index d16ad49..53dbfd3 100644
> --- a/net/bluetooth/l2cap_core.c
> +++ b/net/bluetooth/l2cap_core.c
> @@ -4243,7 +4243,7 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk
>  	u16 tx_seq;
>  	int len;
>  
> -	chan = l2cap_get_chan_by_scid(conn, cid);
> +	chan = __l2cap_get_chan_by_scid(conn, cid);
>  	if (!chan) {
>  		if (cid == L2CAP_CID_A2MP) {
>  			chan = a2mp_channel_create(conn, skb);
> @@ -4255,6 +4255,8 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk
>  	}
>  
>  	sk = chan->sk;
> +	if (sk)
> +		lock_sock(sk);

this is the part I clearly do not like. This is pretty nasty conditional
locking. We need to figure out something better.

Regards

Marcel