linux-kernel - Re: suspend blockers & Android integration

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Date:	Sun, 6 Jun 2010 02:19:40 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Arve Hjønnevåg <arve@...roid.com>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, tytso@....edu,
	Brian Swetland <swetland@...gle.com>,
	Neil Brown <neilb@...e.de>,
	Alan Stern <stern@...land.harvard.edu>,
	Felipe Balbi <felipe.balbi@...ia.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Florian Mickler <florian@...kler.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Linux PM <linux-pm@...ts.linux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	James Bottomley <James.Bottomley@...e.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Kevin Hilman <khilman@...prootsystems.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: suspend blockers & Android integration

On Sat, 5 Jun 2010, Arve Hjønnevåg wrote:
> 2010/6/5 Thomas Gleixner <tglx@...utronix.de>:
> >> > Well, that's simply an application bug which sucks battery with or
> >> > without suspend blockers. So it's unrelated to the freezing of
> >> > untrusted apps while a trusted app still works in the background
> >> > before allowing the machine to suspend.
> >> >
> >>
> >> It is not unrelated if the trusted app has stopped working but still
> >> blocks suspend. The battery drains when you combine them.
> >
> > What you are describing is a problem which is not solvable either way.
> > If you take the lock and do not release it you're not going to
> > suspend. I never claimed that any other mechanism resolves this.
> >
> Whether you claimed it or not, this is the only case where using
> cgroups would have a significant power saving over what we get with
> suspend. The trusted app is idle and the untrusted app is frozen, so
> we enter a low power mode from idle.

Nothing else was what I said and depending on the usage pattern this
can be significant. Just you converted a perfectly sensible technical
argument into a quibble about BUGs in applicatins which are not
confinable by defintion.
 
> > But this is not related to the fact that freezing crap while running a
> > sane background task is going to save you power vs. an approach where
> > running a sane background task allows crap to consume power unconfined
> > until it is done.
> >
> If the task that is blocking suspend is using the cpu anyway, then the
> bad app does not increase the power consumption nearly as much as if
> the task that blocked suspend is idle.

That's utter bullshit. If the app missed to release the supsend
blocker then your crappy "while(1);" app is killing you in no time,
while the same frozen crappy "while(1);" does no harm at all.
 
Thanks,

	tglx