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Date: Fri, 19 Jul 2013 07:32:47 +0200
From: Andre Albsmeier <Andre.Albsmeier@siemens.com>
To: Konstantin Belousov <kostikbel@gmail.com>
Subject: Re: FreeBSD-9.1: machine reboots during snapshot creation, LORs found
Message-ID: <20130719053247.GA72555@bali>
References: <20130531122611.GA6607@bali> <201305311051.03157.jhb@freebsd.org>
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On Thu, 04-Jul-2013 at 19:25:28 +0200, Konstantin Belousov wrote:
> On Thu, Jul 04, 2013 at 04:29:19PM +0200, Andre Albsmeier wrote:
> > OK, patch is applied. I will reboot the machine later
> > and see what happens tomorrow in the morning. However,
> > it might take a few days since the last 2 weeks all was
> > fine.
> > 
> > BTW, should this patch be used in general or is it just
> > for debugging? My understanding is that it is something
> > which could stay in the code...
> 
> Patch is to improve debugging.
> 
> 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.

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.

	-Andre