Date: Wed, 9 May 2007 11:43:05 +0200
From: Johannes Stezenbach <js@linuxtv.org>
To: Jonathan Corbet <corbet@lwn.net>
Cc: Randy Dunlap <randy.dunlap@oracle.com>,
       Paul Sokolovsky <pmiscml@gmail.com>, linux-kernel@vger.kernel.org,
       Andrew Morton <akpm@linux-foundation.org>
Message-ID: <20070509094305.GC28774@linuxtv.org>
References: <20070508121404.17bd97a6.randy.dunlap@oracle.com> <16987.1178675251@lwn.net>
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Subject: Re: [RFC/PATCH] doc: volatile considered evil
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On Tue, May 08, 2007, Jonathan Corbet wrote:
> 
> I just took a shot at turning this into something more like a normal
> document:
> 
> 	http://lwn.net/Articles/233479/

I think the "jiffies variable is special" part misses the
"for stupid legacy reasons" explanation.

According to the other volatile rules one should use
something like that:

extern unsigned long __jiffies;
static inline unsigned long read_ulong(unsigned long *addr)
{
	return *(volatile unsigned long *)addr;
}
static inline unsigned long get_jiffies(void)
{
	return read_ulong(&__jiffies);
}

But of course changing all references to jiffies in the kernel would
be insane, thus jiffies is special "for stupid legacy reasons".

Right?


Johannes
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