linux-kernel - RE: [PATCH 1/2] x86: mce: kdump: use under_crashdumping to turn off MCE in all CPUs together

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Date:	Tue, 24 Feb 2015 18:47:23 +0000
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Naoya Horiguchi <nao.horiguchi@...il.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Junichi Nomura <j-nomura@...jp.nec.com>,
	Kiyoshi Ueda <k-ueda@...jp.nec.com>
Subject: RE: [PATCH 1/2] x86: mce: kdump: use under_crashdumping to turn off
 MCE in all CPUs together

> If that is the case, the tolerance level might be the better approach
> after all...

We should also take a look at mce_start():

	int cpus = num_online_cpus();

	...

	/*
	 * Wait for everyone.
	 */
	while (atomic_read(&mce_callin) != cpus) {

since offline cpus will still show up to rendezvous ... perhaps "num_present_cpus()"
is the right number??

-Tony