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Date: Thu, 13 May 2010 13:00:04 -0700
From: Tony Lindgren <tony@atomide.com>
To: Matthew Garrett <mjg@redhat.com>
Cc: Alan Stern <stern@rowland.harvard.edu>, Paul Walmsley <paul@pwsan.com>,
       Arve =?utf-8?B?SGrDuG5uZXbDpWc=?= <arve@android.com>,
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       Tejun Heo <tj@kernel.org>, Oleg Nesterov <oleg@redhat.com>,
       Kevin Hilman <khilman@deeprootsystems.com>, magnus.damm@gmail.com,
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       Mark Brown <broonie@opensource.wolfsonmicro.com>,
       Liam Girdwood <lrg@slimlogic.co.uk>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)
Message-ID: <20100513200003.GE3428@atomide.com>
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* Matthew Garrett <mjg@redhat.com> [100513 12:49]:
> On Thu, May 13, 2010 at 12:42:05PM -0700, Tony Lindgren wrote:
> 
> > 1. In the kernel, we add one more timer queue for critical timers.
> >    The current timer queue(s) stay as it is.
> > 
> > 2. We allow selecting the timer based on some flag, the default
> >    behaviour being the current default timer queue.
> > 
> > 3. Then we add next_timer_interupt_critical() to only query the
> >    critical timers along the lines of the current next_timer_interrupt().
> > 
> > 4. We implement a custom pm_idle that suspends the system based on
> >    some logic and checking if next_timer_interrupt_critical() is
> >    empty. If the next_timer_interrupt_critical() does not return
> >    anything, we assume it's OK to suspend the system.
> 
> Ok. So we stick the untrusted bits of userspace on the critical timer 
> list.

I guess you mean the trusted instead of untrusted apps in the userspace
above, the ones that are critical to keep running.

> Now we get a network packet that generates a wakeup event and gets 
> read by an application. What happens if that application can't fully 
> process the packet in a single timeslice?

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.

Regards,

Tony