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SubjectRe: [PATCH] NMI watchdog: setup before enabling NMI watchdog
[Aristeu Rozanski - Mon, Sep 22, 2008 at 02:35:05PM -0400]
| > 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)?
| actually the comment is a bit misleading. we can get other "undocumented"
| NMIs from different sources. Notice that if the nmi_watchdog_tick() doesn't
| identifies it as a performance counter generated NMI (if LAPIC based, IOAPIC
| always assume that the NMI is for the NMI watchdog), a default NMI callback
| will be tried and if it fails, unknown_nmi_error() will be called. The first
| case comes to my head is those NMI buttons present on development machines.
|
| --
| Aristeu
|

Thanks Aristeu!

- Cyrill -


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