Re: [PATCH] NMI watchdog: setup before enabling NMI watchdog

[Cyrill Gorcunov <gorcunov@gmail.com>]

[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 -