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Date: Sat, 30 Aug 2003 15:05:48 -0400 (EDT)
From: Garrett Wollman <wollman@khavrinen.lcs.mit.edu>
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To: Robert Watson <rwatson@freebsd.org>
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cc: freebsd-current@freebsd.org
Subject: Re: Someone help me understand this...?
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<<On Sat, 30 Aug 2003 12:23:35 -0400 (EDT), Robert Watson <rwatson@freebsd.org> said:

> The only way to close this sort of race is to have a notion of a
> unique process identifier that lasts beyond the lifetime of the
> process itself -- i.e., the ability to return EMYSINCERESTREGRESTS
> if you try to signal a process after it has died, and have a
> guarantee that the handle won't be reused.

This is traditionally done by holding an advisory lock on the pid
file; if the file is no longer locked, then the process holding the
lock must have exited.

You could also do it with UUIDs and a more heavyweight signal API.

-GAWollman