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

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Message-ID: <20100804205159.GH24163@linux.vnet.ibm.com>
Date:	Wed, 4 Aug 2010 13:51:59 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Pavel Machek <pavel@....cz>
Cc:	Matthew Garrett <mjg59@...f.ucam.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Arve Hj?nnev?g <arve@...roid.com>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	florian@...kler.org, rjw@...k.pl, stern@...land.harvard.edu,
	swetland@...gle.com, peterz@...radead.org, tglx@...utronix.de,
	alan@...rguk.ukuu.org.uk
Subject: Re: Attempted summary of suspend-blockers LKML thread

On Wed, Aug 04, 2010 at 10:42:08PM +0200, Pavel Machek wrote:
> Hi!
> 
> > > If this doesn't work for the Android folks for whatever reason, another
> > > approach would be to do the freeze in user code, which could track
> > > whether any user-level resources (pthread mutexes, SysV semas, whatever)
> > > where held, and do the freeze on a thread-by-thread basis within each
> > > "victim" application as the threads reach safe points.
> > 
> > The main problem I see with the cgroups solution is that it doesn't seem 
> > to do anything to handle avoiding loss of wakeup events.
> 
> In different message, Arve said they are actually using low-power idle
> to emulate suspend on Android.

Hello, Pavel,

Could you please point me at this message?

							Thanx, Paul

> This came like a bit of a shock to me ("why do they make it so complex
> then"), but... it also means that as soon as you are able to stop
> "unwanted" processing, you can just leave normal cpuidle mechanisms to
> deal with the rest...
> 
> (Of course, you'll also have to fix kernel timers not to beat
> unneccessarily often; still that's better solution that just stoping
> them all and then sprinkling wakelocks all over the kernel to deal
> with obvious bugs it introduces...)
> 									Pavel
> -- 
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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