On Thu, Aug 10, 2017 at 11:26:27AM -0700, Cliff Spradlin wrote:
> This moves the burden of maintaining the socket file to the manager of
> the ptp4l process. However, maintaining a single instance of ptp4l is
> already the responsibility of the process manager. It's more
> straightforward for process managers to manage processes than to clean
> up files after a process exits.
>
> I think a better approach would be to acquire a lockfile/pidfile on
> startup. If the lock fails, then exit immediately with a failure.
> Normal process managers would stay unchanged, and administrators won't
> be able to accidentally start a second copy of ptp4l by hand.
If ptp4l refused to start without the UDS port, the socket itself
could work as a lockfile, right? There would just need to be an option
to disable the socket.
> People who intend to run more than one instance of ptp4l would either
> need to disable the lockfile or choose a different name for the file.
> Alternatively, we could make the lockfile disabled by default, enabled
> by configuration.
>
> On Thu, Aug 10, 2017 at 4:38 AM, Miroslav Lichvar <mlich...@redhat.com> wrote:
> > When a second instance of ptp4l using the same configuration was
> > (accidentally) started, it removed the Unix domain socket of the first
> > instance and prevented communication with it.
> >
> > Remove the unlink() call to let bind() of the second instance fail and
> > run with the UDS port in faulty state.
> >
> > If the socket is not removed on ptp4l exit (e.g. due to crash), the user
> > will have to remove it manually in order to get a working UDS port
> > again.
> > ---
> > uds.c | 2 --
> > 1 file changed, 2 deletions(-)
> >
> > diff --git a/uds.c b/uds.c
> > index d5e8f50..a12d641 100644
> > --- a/uds.c
> > +++ b/uds.c
> > @@ -69,8 +69,6 @@ static int uds_open(struct transport *t, const char
> > *name, struct fdarray *fda,
> > sa.sun_family = AF_LOCAL;
> > strncpy(sa.sun_path, name, sizeof(sa.sun_path) - 1);
> >
> > - unlink(name);
> > -
> > err = bind(fd, (struct sockaddr *) &sa, sizeof(sa));
> > if (err < 0) {
> > pr_err("uds: bind failed: %m");
> > --
> > 2.9.3
> >
> >
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>
--
Miroslav Lichvar
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