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

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Message-ID: <20100507213800.GD28906@srcf.ucam.org>
Date:	Fri, 7 May 2010 22:38:00 +0100
From:	Matthew Garrett <mjg@...hat.com>
To:	Daniel Walker <dwalker@...o99.com>
Cc:	Tony Lindgren <tony@...mide.com>,
	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 Fri, May 07, 2010 at 02:30:20PM -0700, Daniel Walker wrote:
> On Fri, 2010-05-07 at 22:03 +0100, Matthew Garrett wrote:
> 
> > Here's a different example. A process is waiting for a keypress, but 
> > because it's badly written it's also drawing to the screen at 60 frames 
> > per second and preventing the system from every going to idle. How do 
> > you quiesce the system while still ensuring that the keypress will be 
> > delivered to the application?
> 
> To me it's somewhat of a negative for suspend blockers. Since to solve
> the problem you give above you would have to use a suspend blocker in an
> asynchronous way (locked in an interrupt, released in a thread too)
> assuming I understand your example. I've had my share of semaphore
> nightmares, and I'm not too excited to see a protection scheme (i.e. a
> lock) which allows asynchronous usage like suspend blockers. 

Check the input patch for an example of this.

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