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Date:	Thu, 22 May 2014 23:31:08 +0200
From:	Borislav Petkov <>
To:	"Srivatsa S. Bhat" <>
Cc:	"Luck, Tony" <>,
	Andi Kleen <>,
	Peter Zijlstra <>,
	Srinivas Pandruvada <>,
	Jacob Pan <>,
	LKML <>,
	Borislav Petkov <>, Ingo Molnar <>,
	"Wysocki, Rafael J" <>,
	Thomas Gleixner <>,
	"" <>,
	Oleg Nesterov <>
Subject: Re: [PATCH] x86, MCE: Kill CPU_POST_DEAD

On Fri, May 23, 2014 at 02:43:31AM +0530, Srivatsa S. Bhat wrote:
> >> After you move the cmci_rediscover() call, it is now in a place where we are
> >> no longer ignoring frozen (i.e. the old placement did the rediscover even if the
> >> CPU_TASKS_FROZEN bit was set - with the new placement we will skip rediscovery.
> >>
> That's not quite true. The existing code already ignores FROZEN for all the cases,
> by ignoring it at the top of the switch-case itself:

No, Tony's right and you got confused:

Before my change, the code did:

	if (action == CPU_POST_DEAD) {
		/* intentionally ignoring frozen here */

which is only CPU_POST_DEAD *without* the CPU_TASKS_FROZEN bit.

If I move it in the switch-case, cmci_rediscover() *ignores the FROZEN
bit and gets executed for both:


because with the FROZEN bit masked out, they're the same.

But we don't want to execute it for the FROZEN bit - look for the other
two tests for CPU_TASKS_FROZEN in mce.c for an example.

So, before we go and change the FROZEN aspect and break things in
strange ways, let's keep the _FROZEN ignore. I certainly don't want to
go down that road and chase why we needed FROZEN or not.



Sent from a fat crate under my desk. Formatting is fine.
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