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From: Roland McGrath <roland@redhat.com>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Davide Libenzi <davidel@xmailserver.org>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       Ingo Molnar <mingo@elte.hu>, Laurent Riffard <laurent.riffard@free.fr>,
       Pavel Emelyanov <xemul@openvz.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/5] don't panic if /sbin/init exits or killed
In-Reply-To: Oleg Nesterov's message of  Monday, 17 March 2008 02:03:46 +0300 <20080316230346.GA379@tv-sign.ru>
References: <20080316155453.GA20845@tv-sign.ru>
	<20080316221938.D217026F995@magilla.localdomain>
	<20080316230346.GA379@tv-sign.ru>
Message-Id: <20080316233242.DC9E226F995@magilla.localdomain>
Date: Sun, 16 Mar 2008 16:32:42 -0700 (PDT)
Sender: linux-kernel-owner@vger.kernel.org
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> But panic() isn't better? It doesn't provide any useful info.

It is not misleading in the same way.  It's clear that going to look at the
kernel source is not the place to find the root of the problem.

> Well, I think the generic "if we have a chance to survive, we should try
> to survive" rule is good.
> 
> If the boot init dies, at least the admin has a chance to figure out what
> has happened, and -o remount,ro /.

For me and you, I agree.  I think the common case is that there is no admin
prepared to do any such thing, but just someone expecting a reboot to fix
things and preferring that a failing system reboot itself in the middle of
the night rather than wedge.

> Every BUG/BUG_ON in fact means the system is not useable, but still it does
> not panic(), but tries to proceed.

Many production systems probably set panic_on_oops.  Having the init panic
behavior keyed on that seems fine to me.  I just don't like the "kernel bug
at this source line" output when it's not true.


Thanks,
Roland
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