Hi Marcel,
On Sat, Jan 21, 2012 at 05:41:34PM +0100, Marcel Holtmann wrote:
> 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@xxxxxxxxx>
> > ---
> > 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.
Actually l2cap_data_channel function ends with:
<------8<--------------------
| if (sk)
| release_sock(sk);
|
<------8<--------------------
So in _this_ case it looks consistent. But I agree that generally it does
not looks nice. The reason for that is l2cap_chan is locked with socket
lock. Maybe we could create mutex l2cap_lock and functions like
lock_chan(chan) / unlock_chan(chan) and change socket locks in l2cap_core
with these new locks?
Best regards
Andrei Emeltchenko
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