Re: [PATCH 2/2] serial: Add support to Disconnect fd passing connections

[Gustavo Padovan <padovan@profusion.mobi>]

* Luiz Augusto von Dentz <luiz.dentz@gmail.com> [2011-09-07 18:05:08 +0300]:

> Hi Marcel,
> 
> On Wed, Sep 7, 2011 at 3:46 PM, Marcel Holtmann <marcel@holtmann.org> wrote:
> > Hi Luiz,
> >
> >> > yes, you do have to keep track of the client. You wanna do a proper
> >> > shutdown if the client exits unexpectedly. Or forgets to call shutdown.
> >>
> >> I guess the kernel would auto release the socket if the process exit
> >> and nobody else has a reference to it, so if we close our fd after it
> >> has been transferred the only one with reference is the client, iirc
> >> this was a problem to tty because we have to release the devnode to
> >> disconnect which involves ioctl but afaik that is not the case for
> >> sockets and the client can basically call close and be done with it,
> >> right?
> >
> > does dbus-daemon holds the reference for the time of D-Bus message to be
> > in flight between bluetoothd and the client? If not, then we have a race
> > condition here, because we dropped the reference before it ended up on
> > the other side.
> 
> Good question, iirc dbus-daemon does use dup but we better confirm
> with Lennart how this is supposed to work. Anyway if it doesn't then I
> guess it should be fixed in dbus-daemon to do it, otherwise as you
> said it will be racy to transfer fd specially when fd is send in a
> reply.

It does use dup, I just checked on the source code.

	Gustavo