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Date: Tue, 25 Feb 2003 14:17:11 -0500
From: Daniel Jacobowitz <dan@debian.org>
To: "Richard B. Johnson" <root@chaos.analogic.com>
Cc: Linux kernel <linux-kernel@vger.kernel.org>
Subject: Re: atomic_t (24 bits???)
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On Tue, Feb 25, 2003 at 02:11:11PM -0500, Richard B. Johnson wrote:
> 
> In ../linux/include/asm/atomic.h, for versions 2.4.18 and
> above as far as I've checked, there are repeated warnings
> "Note that the guaranteed useful range of an atomic_t is
> only 24 bits."
> 
> I fail to see any reason why as atomic_t is typdefed to a
> volatile int which, on ix86 seems to be 32 bits.
> 
> Does anybody know if this is just some old comments from a
> previous atomic_t type of, perhaps, char[3]?  

There are other platforms where you can't reliably use the whole word. 
Some ARM atomic_t implementations are like this, although I don't know
if the one in the kernel is.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer
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