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Date: Tue, 20 Dec 2005 14:59:26 -0500 (EST)
From: Nicolas Pitre <nico@cam.org>
Subject: Re: [patch 04/15] Generic Mutex Subsystem,
 add-atomic-call-func-x86_64.patch
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To: Arjan van de Ven <arjan@infradead.org>
Cc: Russell King <rmk+lkml@arm.linux.org.uk>,
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On Tue, 20 Dec 2005, Arjan van de Ven wrote:

> on x86 the fastpath is the same for both basically.. is there a
> fundamental reason it can't be for ARM?

ARM prior ARM architecture level 6 (which means about 99% of all ARM 
processors in the field currently) cannot do an atomic 
decrement/increment.  It must be done manually with interrupt disabled.

The only truly atomic instruction it has is a swap which lays itself 
pretty well for mutex support.


Nicolas