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

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Message-Id: <201005132321.59245.rjw@sisk.pl>
Date:	Thu, 13 May 2010 23:21:59 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Matthew Garrett <mjg@...hat.com>
Cc:	Tony Lindgren <tony@...mide.com>,
	Alan Stern <stern@...land.harvard.edu>,
	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>,
	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 Thursday 13 May 2010, Matthew Garrett wrote:
> On Thu, May 13, 2010 at 01:23:20PM -0700, Tony Lindgren wrote:
> > * Matthew Garrett <mjg@...hat.com> [100513 13:03]:
> > > On Thu, May 13, 2010 at 01:00:04PM -0700, Tony Lindgren wrote:
> > > 
> > > > The system stays running because there's something to do. The system
> > > > won't suspend until all the processors hit the kernel idle loop and
> > > > the next_timer_interrupt_critical() returns nothing.
> > > 
> > > At which point an application in a busy loop cripples you.
> > 
> > Maybe you could deal with the misbehaving untrusted apps in the userspace
> > by sending kill -STOP to them when the screen blanks? Then continue
> > when some event wakes up the system again.
> 
> And if that's the application that's listening to the network socket 
> that you want to get a wakeup event from? This problem is hard. I'd love 
> there to be an elegant solution based on using the scheduler, but I 
> really don't know what it is.

I agree and I don't understand the problem that people have with the
opportunistic suspend feature.

It solves a practical issue that _at_ _the_ _moment_ cannot be solved
differently, while there's a growing number of out-of-tree drivers depending
on this framework.  We need those drivers in and because we don't have any
viable alternative at hand, we have no good reason to reject it.

Rafael
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