Return-Path: <cyrus@holtmann.org>
Date: Thu, 18 Oct 2012 10:48:54 +0300
From: Andrei Emeltchenko <andrei.emeltchenko.news@gmail.com>
To: Marcel Holtmann <marcel@holtmann.org>
Cc: Mat Martineau <mathewm@codeaurora.org>, linux-bluetooth@vger.kernel.org,
	gustavo@padovan.org, sunnyk@codeaurora.org
Subject: Re: [PATCHv2 07/19] Bluetooth: Add move channel confirm handling
Message-ID: <20121018074848.GE13545@aemeltch-MOBL1>
References: <1350430593-23565-1-git-send-email-mathewm@codeaurora.org>
 <1350430593-23565-8-git-send-email-mathewm@codeaurora.org>
 <1350494187.26318.119.camel@aeonflux>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
In-Reply-To: <1350494187.26318.119.camel@aeonflux>
List-ID: <linux-bluetooth.vger.kernel.org>

Hi Marcel,

On Wed, Oct 17, 2012 at 10:16:27AM -0700, Marcel Holtmann wrote:
> Hi Mat,
> 
> > After sending a move channel response, a move responder waits for a
> > move channel confirm command.  If the received command has a
> > "confirmed" result the move is proceeding, and "unconfirmed" means the
> > move has failed and the channel will not change controllers.
> > 
> > Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
> > ---
> >  net/bluetooth/l2cap_core.c | 70 ++++++++++++++++++++++++++++++++++++++++++++--
> >  1 file changed, 67 insertions(+), 3 deletions(-)
> > 
> > diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> > index 9663292..ed2c23f 100644
> > --- a/net/bluetooth/l2cap_core.c
> > +++ b/net/bluetooth/l2cap_core.c
> > @@ -1036,6 +1036,42 @@ static void l2cap_move_setup(struct l2cap_chan *chan)
> >  	set_bit(CONN_REMOTE_BUSY, &chan->conn_state);
> >  }
> >  
> > +static void l2cap_move_success(struct l2cap_chan *chan)
> > +{
> > +	BT_DBG("chan %p", chan);
> > +
> > +	if (chan->mode != L2CAP_MODE_ERTM)
> > +		return;
> > +
> > +	switch (chan->move_role) {
> > +	case L2CAP_MOVE_ROLE_INITIATOR:
> > +		l2cap_tx(chan, NULL, NULL, L2CAP_EV_EXPLICIT_POLL);
> > +		chan->rx_state = L2CAP_RX_STATE_WAIT_F;
> > +		break;
> > +	case L2CAP_MOVE_ROLE_RESPONDER:
> > +		chan->rx_state = L2CAP_RX_STATE_WAIT_P;
> > +		break;
> > +	}
> > +}
> > +
> > +static void l2cap_move_revert(struct l2cap_chan *chan)
> > +{
> > +	BT_DBG("chan %p", chan);
> > +
> > +	if (chan->mode != L2CAP_MODE_ERTM)
> > +		return;
> > +
> > +	switch (chan->move_role) {
> > +	case L2CAP_MOVE_ROLE_INITIATOR:
> > +		l2cap_tx(chan, NULL, NULL, L2CAP_EV_EXPLICIT_POLL);
> > +		chan->rx_state = L2CAP_RX_STATE_WAIT_F;
> > +		break;
> > +	case L2CAP_MOVE_ROLE_RESPONDER:
> > +		chan->rx_state = L2CAP_RX_STATE_WAIT_P;
> > +		break;
> > +	}
> > +}
> > +
> >  static void l2cap_chan_ready(struct l2cap_chan *chan)
> >  {
> >  	/* This clears all conf flags, including CONF_NOT_COMPLETE */
> > @@ -4302,11 +4338,12 @@ static inline int l2cap_move_channel_rsp(struct l2cap_conn *conn,
> >  	return 0;
> >  }
> >  
> > -static inline int l2cap_move_channel_confirm(struct l2cap_conn *conn,
> > -					     struct l2cap_cmd_hdr *cmd,
> > -					     u16 cmd_len, void *data)
> > +static int l2cap_move_channel_confirm(struct l2cap_conn *conn,
> > +				      struct l2cap_cmd_hdr *cmd,
> > +				      u16 cmd_len, void *data)
> >  {
> >  	struct l2cap_move_chan_cfm *cfm = data;
> > +	struct l2cap_chan *chan;
> >  	u16 icid, result;
> >  
> >  	if (cmd_len != sizeof(*cfm))
> > @@ -4317,8 +4354,35 @@ static inline int l2cap_move_channel_confirm(struct l2cap_conn *conn,
> >  
> >  	BT_DBG("icid 0x%4.4x, result 0x%4.4x", icid, result);
> >  
> > +	chan = l2cap_get_chan_by_dcid(conn, icid);
> > +	if (!chan)
> > +		goto send_move_confirm_response;
> > +
> > +	if (chan->move_state == L2CAP_MOVE_WAIT_CONFIRM) {
> > +		chan->move_state = L2CAP_MOVE_STABLE;
> > +		if (result == L2CAP_MC_CONFIRMED) {
> > +			chan->local_amp_id = chan->move_id;
> > +			if (!chan->local_amp_id) {
> > +				/* Have moved off of AMP, free the channel */
> > +				chan->hs_hchan = NULL;
> > +				chan->hs_hcon = NULL;
> > +
> > +				/* Placeholder - free the logical link */
> > +			}
> > +			l2cap_move_success(chan);
> > +		} else {
> > +			chan->move_id = chan->local_amp_id;
> > +			l2cap_move_revert(chan);
> > +		}
> > +		chan->move_role = L2CAP_MOVE_ROLE_NONE;
> > +	}
> > +
> > +send_move_confirm_response:
> >  	l2cap_send_move_chan_cfm_rsp(conn, cmd->ident, icid);
> >  
> > +	if (chan)
> > +		l2cap_chan_unlock(chan);
> > +
> 
> still not a big fan of the if (chan) check before the unlock. This way
> of dealing with locks makes my brain hurt ;)

I think in this case the solution would be to invoke
l2cap_send_move_chan_cfm_rsp 2 times: 1st time atfer checking (!chan) and
second time here. Since this message does not need any error code this
looks OK to me.

Best regards 
Andrei Emeltchenko