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

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Message-Id: <200902231548.12821.rjw@sisk.pl>
Date:	Mon, 23 Feb 2009 15:48:11 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Johannes Berg <johannes@...solutions.net>,
	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 Monday 23 February 2009, Ingo Molnar wrote:
> 
> * Rafael J. Wysocki <rjw@...k.pl> wrote:
> 
> > > > Index: linux-2.6/arch/x86/kernel/apm_32.c
> > > > ===================================================================
> > > > --- linux-2.6.orig/arch/x86/kernel/apm_32.c
> > > > +++ linux-2.6/arch/x86/kernel/apm_32.c
> > > 
> > > > +
> > > > +	suspend_device_irqs();
> > > >  	device_power_down(PMSG_SUSPEND);
> > > > +
> > > > +	local_irq_disable();
> > > 
> > > hm, this is a very repetitive pattern, all around the various 
> > > suspend/resume variants. Might make sense to make:
> > > 
> > >   	device_power_down(PMSG_SUSPEND);
> > > 
> > > do the irq line disabling plus the local irq disabling 
> > > automatically. That also means it cannot be forgotten. The 
> > > symmetric action should happen for PMSG_RESUME.
> > > 
> > > Is there ever a case where we want a different pattern?
> > 
> > Even if there's no such case, I prefer to call 
> > local_irq_disable() explicitly in here, so that it's clearly 
> > known where it happens to anyone reading this code.
> 
> That property can be implied in the function name:
> 
>    	device_power_down_irq_disable(PMSG_SUSPEND);
> 
> Open-coding it, if it looks the same in all the cases just 
> increases the chances that someone somewhere copies them 
> incorrectly.

Well, I see your point, but in that case I'd rather couple the disabling of
local interrupts on the CPU with sysdev_suspend and the disabling (or whatever
Eric would like to call that) of device interrupts with device_power_down().

Thanks,
Rafael
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