Date: Tue, 03 Jun 1997 02:05:05 +0100 From: Brian Somers <brian@awfulhak.org> To: Adam David <adam@veda.is> Cc: ache@nagual.pp.ru (=?KOI8-R?B?4c7E0sXKIP7F0s7P1w==?=), cvs-committers@freebsd.org, cvs-all@freebsd.org, cvs-etc@freebsd.org Subject: Re: cvs commit: src/etc rc Message-ID: <199706030105.CAA19996@awfulhak.demon.co.uk> In-Reply-To: Your message of "Mon, 02 Jun 1997 22:27:07 -0000." <199706022227.WAA10666@veda.is>
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[.....]
> I have also seen stale locks, but not on a healthy system.
> (file claims to be locked, but no process holds the lock).
Sounds like a *very* sick system. One that's likely to be
doing other stupid things like SEGVing things for no reason
'cos the descriptor tables are shagged.
> > Modification of each such application is not acceptable solution.
>
> Each such application already uses its own methods, which are demonstrably
> deficient in many cases.
What we need is a set of calls in libutil:
int pfile_create(const char *prog); /* create a pid file, return fd
*/
void pfile_destroy(int fd); /* remove a pid file */
pid_t pfile_read(const char *prog); /* Get pid from file */
And maybe a program that uses pfile_read for use in scripts.
As has already been said, the existence of a lock on an existing
file says whether the process is running or not.
Of course to cater for all eventualities, we may need a "max"
arg in pfile_create and an "n" arg in pfile_read, allowing
more than one of a given process. Or maybe this is over-
complicating things.
If programs want to use this mechanism, they can. Killers
like newsyslog should extract the pid to kill using pfile_read,
therefore disabling it from killing un-cooperating processes
(pfile_read will come up with nothing from a stale file).
> --
> Adam David <adam@veda.is>
>
--
Brian <brian@awfulhak.org>, <brian@freebsd.org>
<http://www.awfulhak.org>;
Don't _EVER_ lose your sense of humour....
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