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From: Arnd Bergmann <arnd@arndb.de>
To: linuxppc-embedded@ozlabs.org
Subject: Re: Is in_le32 and out_le32 atomic?
Date: Fri, 8 Dec 2006 21:15:38 +0100
References: <4579C586.5040809@grandegger.com>
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On Friday 08 December 2006 21:05, Wolfgang Grandegger wrote:
> Can anybody tell me why the spin_* protection is needed? I thought that 
> 32-bit read and write operations are atomic.
> 
The spinlocks are needed to guarantee ordering between the completion of
the i/o access and other code. A typical problem is that a store is
still on its way to the I/O device while the CPU has already left the
function that initiated it, and might call code that relies on the
value having arrived there.

	Arnd <><