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

From: Jan Engelhardt
Date: Thu Feb 22 2007 - 07:38:00 EST

On Feb 22 2007 00:17, Thomas Gleixner wrote:
>On Thu, 2007-02-22 at 00:04 +0100, Luca Tettamanti wrote:
>> 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)

What's the benefit of doing so - and why has not it been done before?
I mean, I run a regular,
/sys/devices/system/clocksource/clocksource0/current_clocksource (is this
related?) shows "acpi_pm", but the IRQ0 counter increases at HZ. Maybe I
am confusing things, but why the need for PIT when clocksource is acpi_pm

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