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Date: Sat, 20 Nov 2004 18:45:18 +1100
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: William Lee Irwin III <wli@holomorphy.com>
CC: Linus Torvalds <torvalds@osdl.org>, Christoph Lameter <clameter@sgi.com>,
       akpm@osdl.org, Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       Hugh Dickins <hugh@veritas.com>, linux-mm@kvack.org,
       linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: touch_nmi_watchdog (was: page fault scalability patch V11 [0/7]:
 overview)
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Nick Piggin wrote:

>> (2) NMI's don't nest. There is no possibility of NMI's racing against
>>     themselves while the data is per-cpu.
>>
> 
> Your point was that touch_nmi_watchdog() which resets alert_counter,
> is racy when resetting the counter of other CPUs. Yes it is racy.
> It is also racy against the NMI on the _current_ CPU.

Hmm no I think you're right in that it is only a problem WRT the remote
CPUs. However that would still be a problem, as the comment in i386
touch_nmi_watchdog attests.