Hi all,
I have configured my kernel (2.6.31.6) so that I get periodic ticks from the
timer interrupt (i.e. tickless is not configured) with a rate determined by
the HZ value. I have also selected the "Local APIC support on uniprocessors"
option so that the LAPIC timer is used as a tick source. The problem is that
the handler used for the timer is not the "local_apic_timer_interrupt"
handler as I was excepted but the "tick_handle_periodic" handler. This can
be verified by seeing the output of /proc/timer_list:
Tick Device: mode: 0
Per CPU device: 0
Clock Event Device: lapic
max_delta_ns: 1006457290
min_delta_ns: 1799
mult: 35797637
shift: 32
mode: 1
next_event: 9223372036854775807 nsecs
set_next_event: lapic_next_event
set_mode: lapic_timer_setup
event_handler: tick_handle_periodic
Is there an explanation for that? The board in which I am running the kernel
is a Kontron 986LCD-M/mITX one with an Intel Celeron M 440 installed on it.
I have verified that Intel Celeron M Processors have a LAPIC and
consequently, a LAPIC timer.
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Another weird thing that I noticed is that by running the same kernel but
configured for "Core 2/newer Xeon" processors, the timer handler used is the
"hrtimer_interrupt" handler. Again, this is verified by /proc/timer_list:
Tick Device: mode: 1
Per CPU device: 0
Clock Event Device: lapic
event_handler: hrtimer_interrupt
I have put some printks inside "local_apic_timer_interrupt" handler which
should never be executed as the handler selected for the timer is
"hrtimer_interrupt" and not "local_apic_timer_interrupt" as verified.
However, when I execute a user process which is just a long time delay, the
printks from the "local_apic_timer_interrupt" are printed.
If you need more info about something, please ask.
Any help will be much appreciated.
Thanks in advance.
P.S. please CC me.
-John
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