From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <andi@firstfloor.org>
Subject: Re: [PATCH] seqlock: serialize against writers
Date: Fri, 29 Aug 2008 18:22:16 +0200
Message-ID: <20080829162216.GW26610@one.firstfloor.org>
References: <20080829154237.1196.66825.stgit@dev.haskins.net> <87abevpzv7.fsf@basil.nowhere.org> <48B81F60.3080409@gmail.com>
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Cc: Andi Kleen <andi@firstfloor.org>,
	Gregory Haskins <ghaskins@novell.com>, mingo@elte.hu,
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> Im running it on a x86_64 box as we speak.  How can I tell if there is a
> certain mode that is permitting this?

If the boot up says you're running with PMtimer then it uses the fallback
(usually happens on pre Fam10h AMD boxes). A typical Intel box
would use the faster ring 3 only TSC path and then explode with your
change I bet. 

Or step with gdb through gettimeofday() and see if it does a syscall.

-Andi