linux-kernel - Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

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Date:	Fri, 14 May 2010 00:07:34 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Matthew Garrett <mjg@...hat.com>,
	Paul Walmsley <paul@...an.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	"Linux-pm mailing list" <linux-pm@...ts.linux-foundation.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	Kevin Hilman <khilman@...prootsystems.com>,
	magnus.damm@...il.com, "Theodore Ts'o" <tytso@....edu>,
	mark gross <mgross@...ux.intel.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Geoff Smith <geoffx.smith@...el.com>,
	Brian Swetland <swetland@...gle.com>,
	Benoît Cousson <b-cousson@...com>,
	linux-omap@...r.kernel.org, Vitaly Wool <vitalywool@...il.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Liam Girdwood <lrg@...mlogic.co.uk>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

On Thursday 13 May 2010, Tony Lindgren wrote:
> * Alan Stern <stern@...land.harvard.edu> [100513 14:36]:
> > On Thu, 13 May 2010, Tony Lindgren wrote:
> > 
> > > Well this is an interesting problem, and once solved will be handy
> > > for all kind of things. My worry is that if it's integrated in it's
> > > current form it will be totally out of control all over the place :(
> > > 
> > > Still hoping we can come up with some clean way that avoid the patching
> > > all over the place part.. How about the following, can you please check
> > > if it would help with your example of guaranteed handling of event:
> > > 
> > > 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.
> > > 
> > > Now to me it sounds if your the input layer and userspace handle
> > > both grab the timers with the critical flags, it should be guaranteed
> > > that the events get handled before the system is suspended.
> > 
> > Why do you want this to be tied to timers?  Many of the events in 
> > question are asynchronous with no specific timing relations.
> 
> To me it seems that the non-timer related events can be dealt
> with toggling the opportunistic suspend idle flag in sysfs.
> That should depend on the device and use specific policy.

OK, that's all hand waving.  Do you have any patches, please?

Rafael
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