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    SubjectRe: nmi_watchdog=2 regression in 2.6.21
    On 2007.08.31 09:35:23 -0700, Daniel Walker wrote:
    > On Fri, 2007-08-31 at 09:21 -0700, Stephane Eranian wrote:
    > > In this patch, the setup_*() routine now extract the MSR from the wd_ops
    > > to copy them into the nmi_watchdog_ctlblk. This is not done for P4 because
    > > of the special and ugly case of HT.
    > >
    > > With this approach, we can now create a custom wd_ops for CoreDuo that is
    > > a clone of the intel_arch_wd_ops, except for the MSR.
    > >
    > > Could you try this one instead?
    >
    > So I tested your patch unchanged and the system boots, and the
    > check_nmi_watchdog() passes .. However, the nmi stops ticking right
    > after bootup,
    >
    > >>From my /proc/interrupts below,
    >
    > CPU0 CPU1 CPU2 CPU3
    > 0: 108 0 0 0 IO-APIC-edge timer
    > 1: 0 0 0 8 IO-APIC-edge i8042
    > 4: 3427 0 0 1 IO-APIC-edge serial
    > 8: 1 0 0 1 IO-APIC-edge rtc
    > 12: 0 0 0 113 IO-APIC-edge i8042
    > 14: 1128 0 0 10 IO-APIC-edge ide0
    > 16: 1664 0 0 1 IO-APIC-fasteoi uhci_hcd:usb2, eth0
    > 18: 0 0 0 0 IO-APIC-fasteoi ehci_hcd:usb1
    > 19: 0 0 0 0 IO-APIC-fasteoi uhci_hcd:usb3
    > 20: 0 0 0 1 IO-APIC-fasteoi acpi
    > NMI: 1670 1453 1097 967
    > LOC: 48001 48002 48000 48006
    > ERR: 0
    > MIS: 0
    >
    >
    > The NMI field never changes ..
    >
    > So I added another change which looked appropriate,
    >
    > @@ -674,6 +688,7 @@ unsigned lapic_adjust_nmi_hz(unsigned hz
    > {
    > struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
    > if (wd->perfctr_msr == MSR_P6_PERFCTR0 ||
    > + wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR0 ||
    > wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR1)
    > hz = adjust_for_32bit_ctr(hz);
    > return hz;
    >
    >
    > Unfortunately that didn't fix anything, but I have a feeling is has

    That's because MSR_P6_PERFCTR0 is the same as MSR_ARCH_PERFMON_PERFCTR0.
    But I'd personally add that change anyway, as it makes the code less
    tricky and the compiler should optimize it away.

    > something to do with the nmi hertz adjustment that happens after
    > check_nmi_watchdog() ..

    Hm hm, does the same thing (watchdog stuck after check) happen with
    older kernels, ie. those before Stephane's changeset that made it use
    PERFCTR1?

    Maybe you could "activate" the Dprintk in write_watchdog_counter32() to
    see which value gets written to the MSR? (I don't see any switch to
    activate it, so maybe just s/Dprintk(/printk(KERN_WHATEVER / ?)

    Thanks,
    Björn
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