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Date: Fri, 7 May 2010 18:50:25 +0100
From: Matthew Garrett <mjg@redhat.com>
To: Tony Lindgren <tony@atomide.com>
Cc: Brian Swetland <swetland@google.com>,
       Alan Stern <stern@rowland.harvard.edu>,
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       Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.
Message-ID: <20100507175025.GA23952@srcf.ucam.org>
References: <20100506170956.GA28104@srcf.ucam.org> <20100506171453.GC30928@atomide.com> <20100506172201.GA28578@srcf.ucam.org> <20100506173807.GD30928@atomide.com> <20100506174331.GA29103@srcf.ucam.org> <20100506183335.GE30928@atomide.com> <20100506184418.GA30669@srcf.ucam.org> <20100507020541.GH30928@atomide.com> <20100507171218.GA23142@srcf.ucam.org> <20100507173549.GF387@atomide.com>
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On Fri, May 07, 2010 at 10:35:49AM -0700, Tony Lindgren wrote:
> * Matthew Garrett <mjg@redhat.com> [100507 10:08]:
> > The situation is this. You've frozen most of your userspace because you 
> > don't trust the applications. One of those applications has an open 
> > network socket, and policy indicates that receiving a network packet 
> > should generate a wakeup, allow the userspace application to handle the 
> > packet and then return to sleep. What mechanism do you use to do that?
> 
> I think the ideal way of doing this would be to have the system running
> and hitting some deeper idle states using cpuidle. Then fix the apps
> so timers don't wake up the system too often. Then everything would
> just run in a normal way.

Effective power management in the face of real-world applications is a 
reasonable usecase.

> For the misbehaving stopped apps, maybe they could be woken
> to deal with the incoming network data with sysfs_notify?

How would that work? Have the kernel send a sysfs_notify on every netwrk 
packet and have a monitor app listen for it and unfreeze the rest of 
userspace if it's frozen? That sounds expensive.

-- 
Matthew Garrett | mjg59@srcf.ucam.org