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Date: Fri, 20 Mar 2009 13:37:34 +0700
From: Eugene Grosbein <eugen@kuzbass.ru>
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To: Kostik Belousov <kostikbel@gmail.com>
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Cc: stable@freebsd.org
Subject: Re: sysctl lock in RELENG_6
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Kostik Belousov wrote:
> 
> On Tue, Feb 10, 2009 at 11:01:25AM +0700, Eugene Grosbein wrote:
> > On Mon, Feb 09, 2009 at 11:48:22PM +0200, Kostik Belousov wrote:
> >
> > > > I've digged commit logs a bit and found this change MFC'd to RELENG_7
> > > > but not RELENG_6:
> > > >
> > > > http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/kern/kern_sysctl.c#rev1.177.6.2
> > > >
> > > > It seems RELENG_6 needs this too, doesn't it?
> > > > I'm going to merge the change to RELENG_6 and give it a try.
> > >
> > > Yes, please give it a try. In fact, it was quite specific situation
> > > that I observed and produced a fix for. You need execing process that
> > > needs to grab Giant, e.g. due to image being located on !MPSAFE fs, and
> > > simultaneous sysctl issued that inspects this process.
> >
> > Well, my 6.3-STABLE locked very often (sometimes every hour).
> > Yesterday I've upgraded it to 6.4-STABLE, applied 1.177.2.1 of the file
> > to sources, rebuilt NanoBSD image and ran it. It has not locked yet.
> Can you be slightly more scientific in your tests ?
> Try RELENG_6 without my patch to see whether it is needed at all.

Well, there was pretty long testing period (over a month) and I conclude:

1. 6.4-STABLE without your patch hangs.
2. 6.4-STABLE with your patch does not.

Eugene Grosbein