linux-kernel - Re: [PATCH] NMI watchdog: setup before enabling NMI watchdog

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Message-ID: <20080922180535.GB22024@localhost>
Date:	Mon, 22 Sep 2008 22:05:35 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Aristeu Rozanski <aris@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	dzickus@...hat.com, prarit@...hat.com, vgoyal@...hat.com
Subject: Re: [PATCH] NMI watchdog: setup before enabling NMI watchdog

[Aristeu Rozanski - Mon, Sep 22, 2008 at 01:13:59PM -0400]
| There's a small window when NMI watchdog is being set up that if any NMIs
| are triggered, the NMI code will make make use of not initalized wd_ops
| elements:

Hi Aristeu,

thanks for the patch! I may be _absolutely_ wrong but could you
explain me how we reach this site in traps

---
	if (!(reason & 0xc0)) {
		if (notify_die(DIE_NMI_IPI, "nmi_ipi", regs, reason,
				2, SIGINT) == NOTIFY_STOP)
			return;
		/*
		 * Ok, so this is none of the documented NMI sources,
		 * so it must be the NMI watchdog.
			 ^^^^
		 */
		if (nmi_watchdog_tick(regs, reason))
			return;
		if (!do_nmi_callback(regs, cpu))
			unknown_nmi_error(reason, regs);

		return;
	}
---

not having masked APIC registers as NMI entry yet (which is done during
perfctl initialization)?

		- Cyrill -
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