linux-kernel - Re: [patch] fix emergency reboot: call reboot notifier list if possible

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Message-ID: <20070123195712.GB6596@ucw.cz>
Date:	Tue, 23 Jan 2007 19:57:12 +0000
From:	Pavel Machek <pavel@....cz>
To:	Andrew Morton <akpm@...l.org>
Cc:	Ingo Molnar <mingo@...e.hu>, rmk+lkml@....linux.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] fix emergency reboot: call reboot notifier list if possible

Hi!

> > > On Wed, Jan 17, 2007 at 10:13:19AM +0100, Ingo Molnar wrote:
> > > > we dont call the reboot notifiers during emergency reboot mainly because 
> > > > it could be called from atomic context and reboot notifiers are a 
> > > > blocking notifier list. But actually the kernel is often perfectly 
> > > > reschedulable in this stage, so we could as well process the 
> > > > reboot_notifier_list.
> > > 
> > > My experience has been that when there has been the need to use this
> > > facility, the kernel hasn't been reschedulable. [...]
> > 
> > this decision is totally automatic - so if your situation happens and 
> > the kernel isnt reschedulable, then the notifier chain wont be called 
> > and nothing changes from your perspective. Hm, perhaps this should be 
> > dependent on CONFIG_PREEMPT, to make sure preempt_count() is reliable?
> > 
> > but from my perspective this patch fixes a real regression.
> > 
> > updated patch attached below.
> > 
> 
> Making it dependent upon CONFIG_PREEMPT seems a bit sucky.  Perhaps pass in
> some "you were called from /proc/sysrq-trigger" notification?

What about adding 'B' with 'reboot with notifications' meaning?
							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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