linux-kernel - Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

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Date:	Fri, 14 May 2010 22:35:41 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Tony Lindgren <tony@...mide.com>, Paul Walmsley <paul@...an.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	Kevin Hilman <khilman@...prootsystems.com>,
	<magnus.damm@...il.com>, Theodore Ts'o <tytso@....edu>,
	mark gross <mgross@...ux.intel.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Geoff Smith <geoffx.smith@...el.com>,
	Brian Swetland <swetland@...gle.com>,
	Matthew Garrett <mjg@...hat.com>,
	Benoît Cousson <b-cousson@...com>,
	<linux-omap@...r.kernel.org>, Vitaly Wool <vitalywool@...il.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Liam Girdwood <lrg@...mlogic.co.uk>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

On Fri, 14 May 2010, Rafael J. Wysocki wrote:

> > > How do you handle situations where the CPU is currently idle but an 
> > > event (such as I/O completion) is expected to occur in the near future?  
> > > You don't want to power-off and reboot then, do you?
> > 
> > The idle code looks at next_timer_interrupt() value, then if the
> > next timer event if far enough ahead, the system powers down and
> > wakes to the timer interrupt. It also wakes to device interrupts.
> 
> For the record, waking to interrupts doesn't work on quite some systems
> (like ACPI-based PCs for one example).

Ironically, it appears that ACPI-based PCs are in a position to benefit 
more from opportunistic suspend and suspend blockers than are embedded 
systems -- and yet they are being proposed for use on cell phones 
rather than on desktops.

Alan Stern

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