Re: NO_HZ: timer interrupt stuck [Re: Linux 2.6.21-rc1]

[Thomas Gleixner <tglx@linutronix.de>]

On Thu, 2007-02-22 at 00:04 +0100, Luca Tettamanti wrote:
> Hi Thomas,
> I'm testing NO_HZ on my machines. On the laptop I see that the timer
> interrupt counter is incremented (though slower than HZ). This machine
> is running UP kernel.
> 
> On my desktop I see this:
> 
>            CPU0       CPU1       
>   0:        114          0   IO-APIC-edge      timer
>   1:       1624      10771   IO-APIC-edge      i8042
>   6:          3          0   IO-APIC-edge      floppy
>   7:          0          0   IO-APIC-edge      parport0
>   9:          0          0   IO-APIC-fasteoi   acpi
>  12:      40111     184047   IO-APIC-edge      i8042
>  16:      75624     998858   IO-APIC-fasteoi   radeon@pci:0000:01:00.0, uhci_hcd:usb1
>  17:          0          0   IO-APIC-fasteoi   uhci_hcd:usb4
>  18:        711       5487   IO-APIC-fasteoi   ide1, libata, ehci_hcd:usb7, uhci_hcd:usb3
>  19:        617       2254   IO-APIC-fasteoi   libata, uhci_hcd:usb2
>  20:          0          0   IO-APIC-fasteoi   ehci_hcd:usb6, uhci_hcd:usb5
>  21:    2483869          0   IO-APIC-fasteoi   eth0
>  22:          2          0   IO-APIC-fasteoi   ohci1394
> 218:      28872     360643   PCI-MSI-edge      HDA Intel
> 219:      32932     138196   PCI-MSI-edge      libata
> NMI:          0          0 
> LOC:    2761191    2827539 
> ERR:          0
> MIS:          0
> 
> Interrupt 0 is stuck at 114 (the number is consistent across reboots). I
> don't experience any problem, time is running fine. Still it's strange
> that the timer is doing nothing; maybe something other than the PIT is
> used for time keeping?

Yes, we switch away from PIT and use the local APIC timer. (LOC)

	tglx


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