linux-kernel - Re: [PATCH 1/8] PM: Opportunistic suspend support.

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Date:	Wed, 26 May 2010 12:06:24 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Arve Hjønnevåg <arve@...roid.com>
Cc:	Florian Mickler <florian@...kler.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Randy Dunlap <rdunlap@...otime.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Tejun Heo <tj@...nel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Nigel Cunningham <nigel@...onice.net>,
	Ming Lei <tom.leiming@...il.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	linux-doc@...r.kernel.org, Matthew Garrett <mjg59@...f.ucam.org>,
	Greg KH <gregkh@...e.de>, tytso@....edu,
	James Bottomley <James.Bottomley@...e.de>
Subject: Re: [PATCH 1/8] PM: Opportunistic suspend support.

On Wed, 2010-05-26 at 02:54 -0700, Arve Hjønnevåg wrote:
> 
> I'm not sure what you are proposing that we use instead. Both
> user-space and kernel code needs to block suspend. If we don't have
> suspend blockers in the kernel then user-space needs to poll when a
> driver blocks suspend by returning an error from its suspend hook. 

In particular I'm suggesting you ditch the /dev/suspend_block thing.

With a single suspend manager process that manages the suspend state you
can achieve the same goal.

When the suspend manager has a !0 busy-task count, it ensures the kernel
won't auto-suspend, when it again reaches a 0 busy-task count, it
re-instates the auto-suspend feature.

That's pretty much what that device would do too.

Ideally we would not do the auto-suspend thing at all and have
runtime-PM improved. Not running apps when they expect to run is like
the world turned upside down.

'Evil' apps could always report themselves as blocker anyway.
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