linux-kernel - Re: [RFC PATCH] waitfd: file descriptor to wait on child processes

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Message-ID: <20081209190403.2731dfd0@lxorguk.ukuu.org.uk>
Date:	Tue, 9 Dec 2008 19:04:03 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Casey Dahlin <cdahlin@...hat.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Scott James Remnant <scott@...split.com>
Subject: Re: [RFC PATCH] waitfd: file descriptor to wait on child processes

> > This propogates the fundamental braindamage of waitpid - the fact the
> > notification only works on child process trees.
> >
> > Here is a more elegant suggestion - use epoll, inotify and friends  fully
> > on /proc process nodes.

> Last I checked inotify was not supported in /proc, or at least most of 
> it. What kind of work load is it to change that?

I don't know but I think it would be the better approach to find it. That
also separates notification of state to parents from the general problem
of wanting to know when a service has died, which seems to be an ever
more common point of interest on the desktop in particular.

File content change notification for /proc is hard because the contents
don't exist in the normal way and get updated but can be done if there is
a wait queue for the job. Actual changes to structure (new directories
etc) is in part a similar problem but there are clear points already in
existence when the proc nodes are created/destroyed and thus notification
can occur.
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