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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Matthew Garrett <mjg@redhat.com>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)
Date: Thu, 13 May 2010 23:21:59 +0200
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Cc: Tony Lindgren <tony@atomide.com>, Alan Stern <stern@rowland.harvard.edu>,
       Paul Walmsley <paul@pwsan.com>,
       Arve =?iso-8859-1?q?Hj=F8nnev=E5g?= <arve@android.com>,
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       Kevin Hilman <khilman@deeprootsystems.com>, magnus.damm@gmail.com,
       "Theodore Ts'o" <tytso@mit.edu>, mark gross <mgross@linux.intel.com>,
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       Brian Swetland <swetland@google.com>,
       =?iso-8859-1?q?Beno=EEt_Cousson?= <b-cousson@ti.com>,
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       Liam Girdwood <lrg@slimlogic.co.uk>
References: <alpine.DEB.2.00.1005122118530.7624@utopia.booyaka.com> <20100513202320.GF3428@atomide.com> <20100513203412.GA21244@srcf.ucam.org>
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On Thursday 13 May 2010, Matthew Garrett wrote:
> On Thu, May 13, 2010 at 01:23:20PM -0700, Tony Lindgren wrote:
> > * Matthew Garrett <mjg@redhat.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.
> 
> And if that's the application that's listening to the network socket 
> that you want to get a wakeup event from? This problem is hard. I'd love 
> there to be an elegant solution based on using the scheduler, but I 
> really don't know what it is.

I agree and I don't understand the problem that people have with the
opportunistic suspend feature.

It solves a practical issue that _at_ _the_ _moment_ cannot be solved
differently, while there's a growing number of out-of-tree drivers depending
on this framework.  We need those drivers in and because we don't have any
viable alternative at hand, we have no good reason to reject it.

Rafael