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

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Message-Id: <200903112301.51594.rjw@sisk.pl>
Date:	Wed, 11 Mar 2009 23:01:50 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Ingo Molnar <mingo@...e.hu>,
	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:
> On Wed, 11 Mar 2009, Rafael J. Wysocki wrote:
> > On Wednesday 11 March 2009, Thomas Gleixner wrote:
> > > > +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.
> 
> I don't say that the difference is not relevant. But the code is
> almost the same and disable_irq() could have the sync_irq optimization
> as well.

Agreed.

> > >   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.
> 
> Hmrpf. Will do. I just want to avoid that we have scattered functions
> which deal with the guts of the irq code all over the place.

I understand your concern, I'd prefer to avoid that too.

> I'm fine with your loop in irq/pm.c, but the actual handling of the irq
> internals should remain in manage.c.

Well, perhaps we can add a parameter to disable_irq_nosync() telling it not
to disable the interrupt if it's a timer one?  Something like

void disable_irq_nosync(unsigned int irq, bool skip_timer) etc.?

Also, it could return a value meaning whether or not the interrupt has been
actually disabled.

> I'll have a closer look how to solve this.

Thanks!

Best,
Rafael
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