linux-kernel - Re: [update, rev. 6] Re: [PATCH 1/10] PM: Rework handling of interrupts during suspend-resume (rev. 5)

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Date:	Fri, 13 Mar 2009 01:39:50 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	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: [update, rev. 6] Re: [PATCH 1/10] PM: Rework handling of
	interrupts during suspend-resume (rev. 5)


* Rafael J. Wysocki <rjw@...k.pl> wrote:

> On Thursday 12 March 2009, Rafael J. Wysocki wrote:
> > On Wednesday 11 March 2009, Thomas Gleixner wrote:
> > > On Wed, 11 Mar 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.
> > > 
> > > Thought more about that. Avoiding the sync_irq() for irqs which have
> > > no action associated is fine, but you need to catch the following case
> > > as well:
> > > 
> > >    driver code calls disable_irq_nosyc() from the handler (which is
> > >    still running)
> > > 
> > >    suspend code skips the sync due to depth > 0
> > > 
> > > The sync operation is not that expensive.
> > 
> > OK, what about this (untested, irrelevant parts skipped)?
> 
> Well, I guess I need to assume that no reaction means it's fine. ;-)
> 
> Below is the complete patch.  Thomas, Ingo, please let me know 
> it it is fine with you.

looks good - but you sure want to split it up some more, right?

> 13 files changed, 195 insertions(+), 47 deletions(-)

We want the non-intrusive 'add new APIs' bits [which give most 
of the linecount] separated from the 'all hell breaks lose' 
functional changes ;-) Makes it easier to revert, bisect, etc.

	Ingo
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