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 [thread overview]
Message-ID: <200612082115.38812.arnd@arndb.de> (raw)
In-Reply-To: <4579C586.5040809@grandegger.com>
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 <><
next prev parent reply other threads:[~2006-12-08 20:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-08 20:05 Is in_le32 and out_le32 atomic? Wolfgang Grandegger
2006-12-08 20:15 ` Arnd Bergmann [this message]
2006-12-11 6:48 ` Benjamin Herrenschmidt
2006-12-11 8:11 ` Wolfgang Grandegger
2006-12-11 9:05 ` Benjamin Herrenschmidt
2006-12-11 6:47 ` Benjamin Herrenschmidt
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