linux-kernel - Re: [PATCH 3/6] x86-mce: Clear CMCI enable on all claimed CMCI banks before reboot.

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Date:	Wed, 9 Jul 2014 14:40:55 -0700
From:	Havard Skinnemoen <hskinnemoen@...gle.com>
To:	"Luck, Tony" <tony.luck@...el.com>
Cc:	Borislav Petkov <bp@...en8.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ewout van Bekkum <ewout@...gle.com>
Subject: Re: [PATCH 3/6] x86-mce: Clear CMCI enable on all claimed CMCI banks
 before reboot.

On Wed, Jul 9, 2014 at 1:36 PM, Luck, Tony <tony.luck@...el.com> wrote:
> +       if (!xchg(&reboot_notifier_registered, true))
> +               register_reboot_notifier(&cmci_reboot_notifier);
>
> This is super-safe ... but isn't the xchg() overkill? I thought we serialized bringup
> of other cpus.

Could be. There are spinlocks being taken elsewhere in that path
though, and I'm not sure if I see any downside with the xchg(), unless
this path is actually performance-critical.

Havard
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