linux-kernel - Re: down_spin() implementation

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Message-Id: <200803291204.36855.nickpiggin@yahoo.com.au>
Date:	Sat, 29 Mar 2008 12:04:36 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Matthew Wilcox <matthew@....cx>
Cc:	"Luck, Tony" <tony.luck@...el.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-arch@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: down_spin() implementation

On Friday 28 March 2008 23:45, Matthew Wilcox wrote:

> I think we can do better here with:
>
> 	atomic_set(max);
>
> and
>
> 	while (unlikely(!atomic_add_unless(&ss->cur, -1, 0)))
> 		while (atomic_read(&ss->cur) == 0)
> 			cpu_relax();

Yeah of course! That's much better ;)

I'd say Tony could just open code it for now, which would get him
up and running quickly... although if anybody gets keen to add it
as a generic API then I wouldn't object.

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