linux-kernel - Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.

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Message-ID: <20100507171218.GA23142@srcf.ucam.org>
Date:	Fri, 7 May 2010 18:12:18 +0100
From:	Matthew Garrett <mjg@...hat.com>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Brian Swetland <swetland@...gle.com>,
	Alan Stern <stern@...land.harvard.edu>,
	mark gross <mgross@...ux.intel.com>, markgross@...gnar.org,
	Len Brown <len.brown@...el.com>, linux-doc@...r.kernel.org,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.

On Thu, May 06, 2010 at 07:05:41PM -0700, Tony Lindgren wrote:
> * Matthew Garrett <mjg@...hat.com> [100506 11:39]:
> > And the untrusted userspace code that's waiting for a network packet? 
> > Adding a few seconds of latency isn't an option here.
> 
> Hmm well hitting retention and wake you can basically do between
> jiffies. Hitting off mode in idle has way longer latencies,
> but still in few hundred milliseconds or so, not seconds.

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?

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