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Date:      Fri, 19 Jul 2013 10:05:41 +0300
From:      Konstantin Belousov <kostikbel@gmail.com>
To:        Andre Albsmeier <Andre.Albsmeier@siemens.com>
Cc:        "freebsd-stable@freebsd.org" <freebsd-stable@freebsd.org>, John Baldwin <jhb@freebsd.org>
Subject:   Re: FreeBSD-9.1: machine reboots during snapshot creation, LORs found
Message-ID:  <20130719070541.GH5991@kib.kiev.ua>
In-Reply-To: <20130719053247.GA72555@bali>
References:  <201305311051.03157.jhb@freebsd.org> <20130616063942.GA72803@bali> <201306171530.31208.jhb@freebsd.org> <20130704051409.GA22021@bali> <20130704052440.GG91021@kib.kiev.ua> <20130704052659.GA23398@bali> <20130704061550.GI91021@kib.kiev.ua> <20130704142919.GA1798@bali> <20130704172528.GL91021@kib.kiev.ua> <20130719053247.GA72555@bali>

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On Fri, Jul 19, 2013 at 07:32:47AM +0200, Andre Albsmeier wrote:
> On Thu, 04-Jul-2013 at 19:25:28 +0200, Konstantin Belousov wrote:
> > Patch is to improve debugging.
> >=20
> > I probably commit it after the issue is closed.  Arguments against
> > the commit is that the change imposes small performance penalty
> > due to save and restore of the %ebp (I doubt that this is measureable
> > by any means).  Also, arguably, such change should be done for all
> > functions in support.s, but bcopy() is the hot spot.
>=20
> Thanks to this patch, we (you ;-) were able to track down the problem.
> So how are we going to deal with this debugging patch itself?
> My suggestion would be to #ifdef it somehow so on one hand it will
> be availabe in future (and with bcopy being used a lot probability
> is high it might help in other places), on the other hand it won't
> steal cycles during normal use.

This was already committed as r253328 in HEAD.  I dislike the #ifdef,
since the stack access is interwinned through all text, making the
function forked.

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