linux-kernel - Re: [PATCH 1/10] PM: Rework handling of interrupts during suspend-resume (rev. 5)

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Date:	Wed, 11 Mar 2009 21:59:19 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>
Cc:	pm list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Len Brown <lenb@...nel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Frans Pop <elendil@...net.nl>,
	Arve Hjønnevåg <arve@...roid.com>
Subject: Re: [PATCH 1/10] PM: Rework handling of interrupts during suspend-resume (rev. 5)

On Wednesday 11 March 2009, Thomas Gleixner wrote:
> Rafael,
> 
> On Wed, 11 Mar 2009, Rafael J. Wysocki wrote:
> 
> > Index: linux-2.6/kernel/irq/pm.c
> > ===================================================================
> > --- /dev/null
> > +++ linux-2.6/kernel/irq/pm.c
> > @@ -0,0 +1,89 @@
> > +/*
> > + * linux/kernel/irq/pm.c
> > + *
> > + * Copyright (C) 2009 Rafael J. Wysocki <rjw@...k.pl>, Novell Inc.
> > + *
> > + * This file contains power management functions related to interrupts.
> > + */
> > +
> > +#include <linux/irq.h>
> > +#include <linux/module.h>
> > +#include <linux/interrupt.h>
> > +
> > +#include "internals.h"
> > +
> > +/**
> > + * suspend_device_irqs - disable all currently enabled interrupt lines
> > + *
> > + * During system-wide suspend or hibernation device interrupts need to be
> > + * disabled at the chip level and this function is provided for this purpose.
> > + * It disables all interrupt lines that are enabled at the moment and sets the
> > + * IRQ_SUSPENDED flag for them.
> > + */
> > +void suspend_device_irqs(void)
> > +{
> > +	struct irq_desc *desc;
> > +	int irq;
> > +
> > +	for_each_irq_desc(irq, desc) {
> > +		unsigned long flags;
> > +		bool sync = false;
> > +
> > +		spin_lock_irqsave(&desc->lock, flags);
> > +
> > +		if (desc->action && !(desc->action->flags & IRQF_TIMER)) {
> > +			if (!desc->depth++) {
> > +				desc->status |= IRQ_DISABLED;
> > +				desc->chip->disable(irq);
> > +				sync = true;
> > +			}
> > +			desc->status |= IRQ_SUSPENDED;
> 
>   This flag needs to be checked in __enable_irq().
> 
> > +		}
> > +
> > +		spin_unlock_irqrestore(&desc->lock, flags);
> > +
> > +		if (sync)
> > +			synchronize_irq(irq);
> > +	}
> > +}
> > +EXPORT_SYMBOL_GPL(suspend_device_irqs);
> 
>   I'm not too enthusiastic about this open coded implementation of
>   disable_irq() with slightly different semantics.

The difference in semantics is important IMO, otherwise I woulndn't have
done that.  In particular, IMO, the condition should be under the spinlock IMO
and I'd rather not synchronize all interrupts we don't really disable here.

>   Can we please move the fiddling with desc->* into
>   kernel/irq/manage.c and share the code there ?

Can you please discuss that with Ingo?  I moved that from manage.c at his
request.

Thanks,
Rafael
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