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

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Date:	Thu, 13 May 2010 13:36:20 -0700
From:	Daniel Walker <dwalker@...o99.com>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Matthew Garrett <mjg@...hat.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>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	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 Thu, 2010-05-13 at 13:23 -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.

Couldn't you just use priorities (nice), or cgroups to deal with that?
I'm sure there is a way to limit an apps runtime, so the system does go
idle sometimes.

> > I think we could implement your suggestion more easily by just giving
> > untrusted applications an effectively infinite amount of timer slack,
> > but it still doesn't handle the case where an app behaves excrutiatingly
> > badly.
> 
> Hmm, if you use timer slack then you still need to search through
> the whole timer list instead of a smaller critical timer list.
> Both ways sound doable though.

There are deferrable timers already in Linux.. It seems like it would
just be an extension of that.

Daniel

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