linux-kernel - Re: [PATCH RFC] x86: avoid atomic operation in test_and_set_bit

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Message-ID: <20110324235654.GM21838@one.firstfloor.org>
Date:	Fri, 25 Mar 2011 00:56:54 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Ingo Molnar <mingo@...e.hu>, Jack Steiner <steiner@....com>,
	Jan Beulich <JBeulich@...ell.com>,
	Borislav Petkov <bp@...64.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Nick Piggin <npiggin@...nel.dk>,
	"x86@...nel.org" <x86@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>, tee@....com,
	Nikanth Karthikesan <knikanth@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH RFC] x86: avoid atomic operation in test_and_set_bit_lock if possible

> never EVER seen any good explanation of why that particular sh*t
> argument would b true. It seems to be purely about politics, where
> some idiotic vendor (namely HP) has convinced Intel that they really
> need it. To the point where some engineers seem to have bought into
> the whole thing and actually believe that fairy tale ("firmware can do
> better" - hah! They must be feeding people some bad drugs at the
> cafeteria)

For the record I don't think it's a good idea for the BIOS to do 
this (and I'm not aware of any engineer who does),  
but I think Linux should do better than just disabling PMU use when 
this happens.

However I suspect taking over SCI would cause endless problems
and is very likely not a good idea.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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