>> After enabling the RTC support, I have recompiled the kernel and try
>> to use the irq 8. But, it seems that the 'irq_request()' can not
>> register my hangler.
>
> isn't that 8 occupied by rtc? and it might be occupied
> exclusively....a.k.a you can put more handler there
The irq 8 is really occupied by rtc and its initial flags is set as
IRQF_DISABLED. At the beginning, I think the irq's registration is
invoked in drivers/char/rtc.c, but this is not really the case. Then,
I have to find where the registration is done. I modified the
request_irq() to the other function name, and compiled the kernel.
Checking the error messages from gcc I found that the actual
registration is done in drivers/rtc/rtc-cmos.c like this:
retval = request_irq(rtc_irq, rtc_cmos_int_handler,
IRQF_DISABLED, dev_name(&cmos_rtc.rtc->dev),
cmos_rtc.rtc);
It is obviously that the irq8 (rtc_irq == 8) is not permitted to be
shared with other interrupt handlers. So, I changed IRQF_DISABLED to
IRQF_SHARED, recompiled the kernel, installed it, and then reboot.
After my module inserted, I get the following messages:
root [ ~ ]# cat /proc/interrupts
CPU0
0: 150 XT-PIC-XT timer
1: 8 XT-PIC-XT i8042
2: 0 XT-PIC-XT cascade
5: 2871 XT-PIC-XT eth0
6: 3 XT-PIC-XT floppy
8: 132 XT-PIC-XT rtc0, myinterrupt
9: 0 XT-PIC-XT acpi
10: 0 XT-PIC-XT uhci_hcd:usb2
11: 45 XT-PIC-XT ioc0, ehci_hcd:usb1
12: 116 XT-PIC-XT i8042
14: 2016 XT-PIC-XT ide0
15: 48 XT-PIC-XT ide1
NMI: 0 Non-maskable interrupts
LOC: 14033 Local timer interrupts
SPU: 0 Spurious interrupts
PMI: 0 Performance monitoring interrupts
PND: 0 Performance pending work
RES: 0 Rescheduling interrupts
CAL: 0 Function call interrupts
TLB: 0 TLB shootdowns
TRM: 0 Thermal event interrupts
THR: 0 Threshold APIC interrupts
MCE: 0 Machine check exceptions
MCP: 8 Machine check polls
The 'rtc0' and 'myinterrupt' share the irq8 really. Then, I executed
the test program from Documentation/rtc.txt to activate some periodic
interrupts from the rtc, and found that the handler of 'myinterrupt'
invoked several times by its output to /var/log/messages.
But I don't think this is an ideal solution to share irq owing to the
modification to kernel code directly. So, I wonder whether there is
any EXPORTed funciton which can modify the flags of an existing
interrupt handler.
2011/8/28 Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx>:
> Hi...
>
> On Sun, Aug 28, 2011 at 03:59, Parmenides <mobile.parmenides@xxxxxxxxx> wrote:
>>> are you really sure? in my system (laptop with core duo cpu) it is
>>> increased by around 1000-2000 every 2 seconds and AFAIK it is using
>>> HPET.
>>>
>> Yes. How can I see the timer is i8253 or HPET? I just found 'timer' in
>> terms of the output of 'cat /proc/interrupts'.
>
> try dumping the output of
> "/sys/devices/system/clocksource/clocksource*/current_clocksource"
>
>>> So maybe IMO free_irq() is causing your cpu referencing null
>>> instruction...that might be due to free_irq is not checking whether it
>>> is safe to delete a handler....
>>>
>
> --
> regards,
>
> Mulyadi Santosa
> Freelance Linux trainer and consultant
>
> blog: the-hydra.blogspot.com
> training: mulyaditraining.blogspot.com
>
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