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Date:      Sun, 8 Nov 1998 11:45:50 -0500 (EST)
From:      Brian Feldman <green@unixhelp.org>
To:        Eivind Eklund <eivind@yes.no>
Cc:        dg@root.com, John Fieber <jfieber@indiana.edu>, current@FreeBSD.ORG
Subject:   Re: The infamous dying daemons bug
Message-ID:  <Pine.BSF.4.05.9811081144340.4580-100000@janus.syracuse.net>
In-Reply-To: <19981108165023.60036@follo.net>

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Is it just me or has noone actually captured the corefiles, compiled
whatever died -g, and tried to debug exactly what caused the sig11? Not
the underlying cause, just the "actual" cause (like a certain register
being a wrong value).

Cheers,
Brian Feldman

On Sun, 8 Nov 1998, Eivind Eklund wrote:

> On Sun, Nov 08, 1998 at 07:17:11AM -0800, David Greenman wrote:
> > >On Sun, Nov 08, 1998 at 09:22:50AM -0500, John Fieber wrote:
> > >> One question: Is the problem "sticky"?  By that I mean, if it is
> > >> triggered by a memomry shortage, is something in the kernel
> > >> corrupted that tends to kill/corrupt daemons from that point in
> > >> time on, or is it just something that affects isolated processes.
> > >
> > >All daemons running at that point seems to get something corrupted.
> > >If you restart the daemon, it won't happen again until you again run
> > >out of memory (or whatever it is that trigger the corruption).
> > 
> >    brk(2) will fail and return ENOMEM if the system is low on swap space.
> 
> phkmalloc() checks for this.
> 
> Anyway; why does it do this?  It does not look like it actually needs
> to do this, and if we do a memory overcommit, it seems to me that we
> could do it all the way (or at least have a sysctl to make it do it
> all the way).  I'm also sorely missing a sysctl to turn off memory
> overcommit...  (I don't know the VM system well enough to implement it
> myself, and I feel very uncomfortable with doing changes in it.)
> 
> > If the application (phk malloc or the caller of malloc?) isn't
> > prepared for this, it may end up with a NULL pointer that it doesn't
> > expect - perhaps not even tripping over it until sometime later.
> 
> I'm pretty sure this is not the problem.  Inactive daemons seems start
> dying, and I don't always get the "out of swap space" message that
> comes with setting swap_pager_full.
> 
> The symptoms are that when the daemon fork after a 'daemons dying
> occurrance', they will immediately get a sig11 on the child fork.
> 
> Eivind.
> 
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