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Date: Fri, 25 Mar 2011 20:26:01 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Andi Kleen <andi@firstfloor.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
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        "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH RFC] x86: avoid atomic operation in test_and_set_bit_lock
 if possible
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* Andi Kleen <andi@firstfloor.org> wrote:

> > Could you please try the patch below?
> 
> This is very likely not a good idea.  I heard some systems can hang
> if you overwrite their PMUs this way and you're unlucky enough :-(

Wrong - in that case all kernels from 2.6.32 to 2.6.38 would already be locking 
up. This patch simply restores behavior to essentially what it was before 
v2.6.38 - but also adds the warning.

Thanks,

	Ingo