linux-kernel - Re: Attempted summary of suspend-blockers LKML thread, take three

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Message-ID: <20100814073843.GA27430@elf.ucw.cz>
Date:	Sat, 14 Aug 2010 09:38:44 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Felipe Contreras <felipe.contreras@...il.com>,
	Ted Ts'o <tytso@....edu>, david@...g.hm,
	Brian Swetland <swetland@...gle.com>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	arve@...roid.com, mjg59@...f.ucam.org, florian@...kler.org,
	rjw@...k.pl, stern@...land.harvard.edu, peterz@...radead.org,
	tglx@...utronix.de, menage@...gle.com, david-b@...bell.net,
	James.Bottomley@...e.de, arjan@...radead.org, swmike@....pp.se,
	galibert@...ox.com, dipankar@...ibm.com
Subject: Re: Attempted summary of suspend-blockers LKML thread, take three

Hi!

> > > > Think in terms of an ARM laptop. What good is opportunistic suspend if
> > > > it's not going to help when the laptop is being used?
> > > 
> > > For when the laptop is not being used, presumably.
> > 
> > Or in time between keystrokes for most of the platform (backlight
> > excepted). The Intel MID x86 devices are at the point that suspend/resume
> > time on x86 is being hurt by the kernel rewriting smp alternatives as we
> > go from 2 processors live to 1 and back.
> 
> Given that you are talking about going from 2 processors to 1 and back,
> I would guess that you are not actually talking about suspend/resume,
> which is a system-wide thing rather than a CPU-by-CPU thing.  I am not
> sure whether you are using CPU hotplug or invoking SMP alternatives once
> all but one CPU is idle.

When entering system suspend, we disable non-boot-CPUs to simplify
locking. We reenable them when going out of suspend.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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