Re: [PATCH] rfcomm: don't release the port in rfcomm_dev_state_change()

[Peter Hurley <peter@hurleysoftware.com>]

On 08/27/2013 12:28 PM, Gianluca Anzolin wrote:
> When the dlc is closed, rfcomm_dev_state_change() tries to release the
> port in the case it cannot get a reference to the tty. However this is
> racy and not even needed.
>
> Infact as Peter Hurley points out:
>
> 1. Only consider dlcs that are 'stolen' from a connected socket, ie.
>     reused. Allocated dlcs cannot have been closed prior to port
>     activate and so for these dlcs a tty reference will always be avail
>     in rfcomm_dev_state_change() -- except for the conditions covered by
>     #2b below.
> 2. If a tty was at some point previously created for this rfcomm, then
>     either
>     (a) the tty reference is still avail, so rfcomm_dev_state_change()
>         will perform a hangup. So nothing to do, or,
>     (b) the tty reference is no longer avail, and the tty_port will be
>         destroyed by the last tty_port_put() in rfcomm_tty_cleanup.
>         Again, no action required.
> 3. Prior to obtaining the dlc lock in rfcomm_dev_add(),
>     rfcomm_dev_state_change() will not 'see' a rfcomm_dev so nothing to
>     do here.
> 4. After releasing the dlc lock in rfcomm_dev_add(),
>     rfcomm_dev_state_change() will 'see' an incomplete rfcomm_dev if a
>     tty reference could not be obtained. Again, the best thing to do here
>     is nothing. Any future attempted open() will block on
>     rfcomm_dev_carrier_raised(). The unconnected device will exist until
>     released by ioctl(RFCOMMRELEASEDEV).
>
> The patch removes the aforementioned code and uses the
> tty_port_tty_hangup() helper to hangup the tty.

Sorry for the delay in reviewing.

Reviewed-by: Peter Hurley <peter@hurleysoftware.com>