Pawel Jakub Dawidek <p...@freebsd.org> writes:
> Dag-Erling Smørgrav <d...@des.no> writes:
> > How do we fix this? My suggestion is to loop until pidfile_open()
> > succeeds or errno != EAGAIN. Does anyone have any objections to that
> > approach?
> I think we already do that internally in pidfile_open(). Can you take a look
> at
> the source and confirm that this is what you mean?
No, it doesn't; pidfile_open(3) returns NULL with errno == EAGAIN if the
pidfile is locked but empty, as is the case in the window between a
successful pidfile_open(3) and the first pidfile_write(3). This is
documented in the man page:
[EAGAIN] Some process already holds the lock on the given pid‐
file, but the file is truncated. Most likely, the
existing daemon is writing new PID into the file.
I have a patch that adds a pidfile to dhclient(8), where I do this:
for (;;) {
pidfile = pidfile_open(path_dhclient_pidfile, 0600, &otherpid);
if (pidfile != NULL || errno != EAGAIN)
break;
sleep(1);
}
if (pidfile == NULL) {
if (errno == EEXIST)
error("dhclient already running, pid: %d.", otherpid);
warning("Cannot open or create pidfile: %m");
}
I'm not sure I agree with the common idiom (which I copied here) of
ignoring all other errors than EEXIST, but that's a different story.
DES
--
Dag-Erling Smørgrav - d...@des.no
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