linux-kernel - Re: [linux-pm] Freezer: Don't count threads waiting for frozen filesystems.

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Message-ID: <20081029235600.GA5993@srcf.ucam.org>
Date:	Wed, 29 Oct 2008 23:56:00 +0000
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Miklos Szeredi <miklos@...redi.hu>, rjw@...k.pl,
	linux-kernel@...r.kernel.org, ncunningham@...a.org.au,
	linux-pm@...ts.linux-foundation.org
Subject: Re: [linux-pm] Freezer: Don't count threads waiting for frozen filesystems.

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@...f.ucam.org
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