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Date: Fri, 7 May 2010 22:38:00 +0100
From: Matthew Garrett <mjg@redhat.com>
To: Daniel Walker <dwalker@fifo99.com>
Cc: Tony Lindgren <tony@atomide.com>, Brian Swetland <swetland@google.com>,
       Alan Stern <stern@rowland.harvard.edu>,
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Subject: Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.
Message-ID: <20100507213800.GD28906@srcf.ucam.org>
References: <20100507184333.GL387@atomide.com> <20100507184621.GA25978@srcf.ucam.org> <1273259186.3542.93.camel@c-dwalke-linux.qualcomm.com> <20100507192837.GM387@atomide.com> <20100507193353.GA27175@srcf.ucam.org> <20100507195548.GN387@atomide.com> <20100507202859.GA27328@srcf.ucam.org> <20100507205329.GP387@atomide.com> <20100507210304.GA28701@srcf.ucam.org> <1273267820.3542.120.camel@c-dwalke-linux.qualcomm.com>
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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@srcf.ucam.org