linux-kernel - Re: [RFC][PATCH 2/2] PM: Rework handling of interrupts during suspend-resume

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Message-Id: <1235404380.4455.13.camel@johannes.local>
Date:	Mon, 23 Feb 2009 07:52:59 -0800
From:	Johannes Berg <johannes@...solutions.net>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Len Brown <lenb@...nel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC][PATCH 2/2] PM: Rework handling of interrupts during
	suspend-resume

On Mon, 2009-02-23 at 12:29 +0100, Rafael J. Wysocki wrote:

> > > +     arch_suspend_disable_irqs();
> > > +     BUG_ON(!irqs_disabled());
> > 
> > Please. We just disabled all devices - a BUG_ON() is a very 
> > counter-productive thing to do here - chances are the user will 
> > never see anything but a hang. So please turn this into a nice 
> > WARN_ONCE().
> 
> This is just moving code.  Also, the BUG_ON() can only affect powerpc and it's
> there on purpose AFAICS (Johannes?).  Anyway, changing that would be a separate
> patch.

It can affect any platform that overrides the weak symbol
arch_suspend_disable_irqs(), and I think that if you're writing this
low-level code you better have a way to debug. As such, I don't think it
needs changing, because you can only ever see that while implementing
arch_suspend_disable_irqs(). OTOH, since it can only trigger then, a
WARN_ON is probably fine as well since you'll be getting your machine
into inconsistent states all the time while implementing this ;)

johannes

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