Re: [PATCH] Bluetooth: Simplify L2CAP timer logic

[Mat Martineau <mathewm@codeaurora.org>]

On Tue, 20 Mar 2012, Andrei Emeltchenko wrote:

> From: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
>
> Simplify L2CAP timers logic. Previous logic was hard to understand.
> Now we always hold(chan) when setting up timer and put(chan) only
> if work pending and we successfully cancel delayed work.
>
> If delayed work is executing it will put(chan) itself.
>
> Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
> ---
> include/net/bluetooth/l2cap.h |   27 ++++++++++++++-------------
> 1 files changed, 14 insertions(+), 13 deletions(-)
>
> diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
> index 9b242c6..e4b2fe7 100644
> --- a/include/net/bluetooth/l2cap.h
> +++ b/include/net/bluetooth/l2cap.h
> @@ -621,29 +621,30 @@ static inline void l2cap_chan_unlock(struct l2cap_chan *chan)
> 	mutex_unlock(&chan->lock);
> }
>
> -static inline void l2cap_set_timer(struct l2cap_chan *chan,
> -					struct delayed_work *work, long timeout)
> -{
> -	BT_DBG("chan %p state %s timeout %ld", chan,
> -					state_to_string(chan->state), timeout);
> -
> -	if (!cancel_delayed_work(work))
> -		l2cap_chan_hold(chan);
> -	schedule_delayed_work(work, timeout);
> -}
> -
> static inline bool l2cap_clear_timer(struct l2cap_chan *chan,
> -					struct delayed_work *work)
> +				     struct delayed_work *work)
> {
> 	bool ret;
>
> -	ret = cancel_delayed_work(work);
> +	ret = (delayed_work_pending(work) && cancel_delayed_work(work));

Why change this?  cancel_delayed_work() can handle a delayed_work that 
is not pending, and has the proper locking to guard against race 
conditions.

> 	if (ret)
> 		l2cap_chan_put(chan);
>
> 	return ret;
> }
>
> +static inline void l2cap_set_timer(struct l2cap_chan *chan,
> +				   struct delayed_work *work, long timeout)
> +{
> +	BT_DBG("chan %p state %s timeout %ld", chan,
> +	       state_to_string(chan->state), timeout);
> +
> +	l2cap_clear_timer(chan, work);
> +
> +	l2cap_chan_hold(chan);
> +	schedule_delayed_work(work, timeout);
> +}
> +
> #define __set_chan_timer(c, t) l2cap_set_timer(c, &c->chan_timer, (t))
> #define __clear_chan_timer(c) l2cap_clear_timer(c, &c->chan_timer)
> #define __set_retrans_timer(c) l2cap_set_timer(c, &c->retrans_timer, \


--
Mat Martineau
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum