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SubjectRE: timer interrupt stucks using tickless kernel
Thanks for the valuable help so far.

>> 2. When performing cat proc/interrupts, I see that:
>> 0: 157 IO-APIC-edge timer
>> How the system timer is attached on IO-APIC at the time that the
>> is disabled on kernel configurations? Basically, the timer is not the
>> only
>> peripheral attached to IO-APIC as can be seen by /proc/interrupts.
>> Here is the output of /proc/interrupts :
>> CPU0
>> 0: 157 IO-APIC-edge timer
>> 1: 2 IO-APIC-edge i8042
>> 4: 544 IO-APIC-edge serial
>> 8: 1 IO-APIC-edge rtc0
>> 9: 0 IO-APIC-fasteoi acpi
>> 12: 4 IO-APIC-edge i8042
>> 14: 4 IO-APIC-edge ata_piix
>> 15: 0 IO-APIC-edge ata_piix
>> 16: 0 IO-APIC-fasteoi uhci_hcd:usb5
>> 18: 0 IO-APIC-fasteoi uhci_hcd:usb4
>> 19: 45 IO-APIC-fasteoi ata_piix, uhci_hcd:usb3
>> 22: 149 IO-APIC-fasteoi HDA Intel
>> 23: 72 IO-APIC-fasteoi ehci_hcd:usb1, uhci_hcd:usb2
>> 27: 0 PCI-MSI-edge eth0
>> NMI: 0 Non-maskable interrupts
>> LOC: 1865130 Local timer interrupts
> ^^^
>This value should be incrementing at HZ freq.

Are you sure about that? ASAIK the Local timer interrupts (generated
by the LAPIC timer) are only used for timekeeping. The system tick is
generated by IRQ0 which in my second configuration should be triggered
by HPET (because I have enabled the HPET timer support). Also, if the
interrupts generated by LAPIC are incremented at HZ freq, why the
interrupts generated by the timer (IRQ0) not happen at the same frequency
as well?

Furthermore, we don't have an answer on why IO-APIC is used at the time
that it is disabled on kernel configurations. The fact that I have enabled
LAPIC timer support doesn't justify the use of the IO-APIC controller
by each own.

>Is there something your actually having problems with here? Ignoring
>which interrupt line is used for the timer event, the system is
>functioning properly, right?

Yes, apart from that, everything is working OK but it's really important
for me to get an answer on these issues.

Kind Regards,

John K.

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