Sadly, that won't work. Both deamons (MM and mine) are started as root. As
far as I know exclusive lock has no power against rooted lock acquire. And
there is no chance not to run my daemon not as root in due to architecture
and interfaces.


2013/6/8 Dan Williams <[email protected]>

> On Fri, 2013-06-07 at 17:43 +0400, Dmitry Ivanyushin wrote:
> > I am working with git version of MM and Ubuntu 12.04.
> >
> > I have three different physical serial (RS232) ports and they are not
> > USB-to-serial. Now MM probes all of them. I want MM to automatically
> detect
> > the port the modem is connected to but there're another devices
> controlled
> > by another daemon.
> >
> > If there were lock files, my daemon wouldn't probe the ports which are
> > locked by MM and vice-versa.
>
> ModemManager does not use lockfiles as there are various well-understood
> problems with them.  It does, however use TIOCEXCL which any other
> program using doing serial stuff should probably be doing too.  Doing it
> through the ioctl means there are no stale lock files left if something
> crashes and no need to write stuff out to random places.
>
> Dan
>
> >
> > 2013/6/7 Aleksander Morgado <[email protected]>
> >
> > >
> > > > I have several serial ports in my system but also I have a daemon
> that
> > > > is responsible for communication with several devices connected to
> those
> > > > serial ports. This daemon runs as root. However when MM starts it
> tries
> > > > to find modem via writing to all serial ports registered in the
> system.
> > > > That operation break protocols of these devices.
> > > >
> > > > I am thinking of adding support of lock-files to MM. Is it good to
> add
> > > > such support in mm-manager.c to test locks, in mm-serial-port to
> acquire
> > > > and release those locks?
> > > >
> > >
> > > What MM version is this? MM shouldn't be probing platform serial
> (RS232)
> > > ports by default, unless they are explicitly white-listed. For USB
> > > devices exposing ttys which aren't modems, we can blacklist them in our
> > > udev rules. Would that help?
> > >
> > > --
> > > Aleksander
> > >
>
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