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Date: Wed, 29 Oct 2008 23:56:00 +0000
From: Matthew Garrett <mjg59@srcf.ucam.org>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Miklos Szeredi <miklos@szeredi.hu>, rjw@sisk.pl,
       linux-kernel@vger.kernel.org, ncunningham@crca.org.au,
       linux-pm@lists.linux-foundation.org
Subject: Re: [linux-pm] Freezer: Don't count threads waiting for frozen filesystems.
Message-ID: <20081029235600.GA5993@srcf.ucam.org>
References: <E1KvDcp-0008B7-SR@pomaz-ex.szeredi.hu> <Pine.LNX.4.44L0.0810291627040.3986-100000@iolanthe.rowland.org>
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On Wed, Oct 29, 2008 at 04:37:30PM -0400, Alan Stern wrote:

> I discussed this last summer with Rafael.  It's a lot harder than it 
> looks, for all sorts of reasons.  For example, what about user tasks 
> that have access to memory-mapped I/O regions?

The only interesting cases of this I know of are X (which ought to stop 
doing so in the near future) and certain sound operations (which are 
going via a well-defined API anyway and need to handle devices going 
away at random, so not a problem). There may be some other niche cases, 
but really - if you're mmapping hardware then it's generally because you 
haven't written a proper kernel driver. Do that instead. Runtime power 
management's already going to make you wildly unhappy.

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