linux-kernel - Re: [PATCH] Replace completions with semaphores

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Date:	Wed, 16 Apr 2008 09:50:26 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	Matthew Wilcox <matthew@....cx>, Ingo Oeser <ioe-lkml@...eria.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Bart Van Assche <bart.vanassche@...il.com>,
	Roland Dreier <rdreier@...co.com>, Ingo Molnar <mingo@...e.hu>,
	Daniel Walker <dwalker@...sta.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Replace completions with semaphores

On Wed, 16 Apr 2008 18:31:08 +0200
Oliver Neukum <oliver@...kum.org> wrote:

> Am Mittwoch, 16. April 2008 18:16:52 schrieb Matthew Wilcox:
> > The basic idea is that you get back a cookie from the
> > kcounter_claim() which you have to hand to the kcounter_release()
> > function so it knows which one you released.  It's similar to mutex
> > debugging except
> 
> So in addition to the kcounter we need to save a token in a data
> structure? In fact, there must be a data structure that can house
> that token. So you can no longer live with a pointer just to a device
> descriptor, but every individual use of a resource must have an
> associated data structure?

yup. For kcounters there is a clear owner for each "slot".
[This is the part that makes it debugable again)

Now for non-debug builds, the space taken for the token can be.. zero 
depending on how we define the types for it.

> 
> 	Regards
> 		Oliver
> 
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