linux-kernel - Re: atomic RAM ?

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Message-ID: <20100409141518.0dbe7050@lxorguk.ukuu.org.uk>
Date:	Fri, 9 Apr 2010 14:15:18 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Michael Schnell <mschnell@...ino.de>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	nios2-dev <nios2-dev@...c.et.ntust.edu.tw>
Subject: Re: atomic RAM ?

> If you think it could be done with NIOS: using store ordering, how can I
> implement a  pthread_mutex_..() workalike ?

Lamport's Bakery is the classic algorithm for doing this. It has very
minimal assumptions about visibility of writes and the order they are
seen so should certainly work uniprocessor and may work SMP depending
upon the cache coherency rules.

It doesn't scale well to large numbers of threads however.

Alan
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