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

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Message-ID: <3908561D78D1C84285E8C5FCA982C28F32857499@ORSMSX114.amr.corp.intel.com>
Date:	Wed, 9 Jul 2014 20:36:35 +0000
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Havard Skinnemoen <hskinnemoen@...gle.com>,
	Borislav Petkov <bp@...en8.de>
CC:	"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.

+	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.

Has this "do it once" caught on elsewhere in the kernel ... I suppose it is more concise than

	if (!reboot_notifier_registered) {
		reboot_notifier_registered = 1;
		register_reboot_notifier(&cmci_reboot_notifier);
	}

-Tony
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