Can not free irq 0

[Parmenides]

Hi,

    I wonder how an interrupt handler work, and so try to make one by
myself. The first problem is which irq number should I select to hook
an interrupt handler on it. In terms of the following messages, I
think irq 0 can be adopted because the number of interrupts raised
remains 145 and does not increase any more. This case may imply the
interrupt handler of rtc clock is not working and can be replaced by
another one. Furthermore, I also notice that the Local timer
interrupts is increasing, and guess that the clock ticks are driven by
this clock chip. That means the irq 0 may be deprecated and its
handler can be replaced safely.

root [ ~/work/moduleprog ]# cat /proc/interrupts
           CPU0
  0:        145    XT-PIC-XT        timer         <---- is not working
  1:          8    XT-PIC-XT        i8042
  2:          0    XT-PIC-XT        cascade
  5:        402    XT-PIC-XT        eth0
  6:          3    XT-PIC-XT        floppy
  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:        750    XT-PIC-XT        ide0
 15:         48    XT-PIC-XT        ide1
NMI:          0   Non-maskable interrupts
LOC:       4932   Local timer interrupts     <---- is working really
SPU:          0   Spurious interrupts
...	...	...	...	...

     The kernel module code:

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>

static irqreturn_t my_interrupt(int irq, void *dev)
{
     return IRQ_HANDLED;
}

int init_module(void)
{
     free_irq(0, NULL);
     if (request_irq(0, my_interrupt, IRQF_SHARED, "myinterrupt",
(void *)my_interrupt)){
          printk(KERN_ALERT "Can not install interrupt handler of irq 0.\n");
     }

     return 0;
}

void cleanup_module(void)
{
}

MODULE_LICENSE("GPL");
MODULE_AUTHOR("parmenides");
MODULE_SUPPORTED_DEVICE("mydevice");

Compile it and then invork insmod, I get these messages:

Aug 27 23:18:35 lfs kernel: ------------[ cut here ]------------
Aug 27 23:18:35 lfs kernel: kernel BUG at mm/slab.c:521!
Aug 27 23:18:35 lfs kernel: invalid opcode: 0000 [#1] SMP
Aug 27 23:18:35 lfs kernel: last sysfs file: /sys/kernel/uevent_seqnum
Aug 27 23:18:35 lfs kernel: Modules linked in: mydevice(+)
Aug 27 23:18:35 lfs kernel:
Aug 27 23:18:35 lfs kernel: Pid: 1688, comm: insmod Not tainted 2.6.34
#1 440BX Desktop Reference Platform/VMware Virtual Platform
Aug 27 23:18:35 lfs kernel: EIP: 0060:[<c108a835>] EFLAGS: 00010046 CPU: 0
Aug 27 23:18:35 lfs kernel: EIP is at kfree+0x67/0x96
Aug 27 23:18:35 lfs kernel: EAX: 00000000 EBX: c155eb40 ECX: 00000000
EDX: c16cdde0
Aug 27 23:18:35 lfs kernel: ESI: 00000282 EDI: c156fc80 EBP: 00000000
ESP: cf323f70
Aug 27 23:18:35 lfs kernel:  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
Aug 27 23:18:35 lfs kernel: Process insmod (pid: 1688, ti=cf322000
task=cfbaa030 task.ti=cf322000)
Aug 27 23:18:35 lfs kernel: Stack:
Aug 27 23:18:35 lfs kernel:  c155eb40 00000000 00000000 c1054076
d0846080 00000000 d0846007 d0846010
Aug 27 23:18:35 lfs kernel: <0> c100112d d0846080 00000000 f63d4e2e
cf322000 c10517ce 0804b018 080488f0
Aug 27 23:18:35 lfs kernel: <0> c138ba4d 0804b018 00000826 0804b008
080488f0 f63d4e2e bfddbfb8 00000080
Aug 27 23:18:35 lfs kernel: Call Trace:
Aug 27 23:18:35 lfs kernel:  [<c1054076>] ? free_irq+0x2e/0x40
Aug 27 23:18:35 lfs kernel:  [<d0846007>] ? init_module+0x0/0x3d [mydevice]
Aug 27 23:18:35 lfs kernel:  [<d0846010>] ? init_module+0x9/0x3d [mydevice]
Aug 27 23:18:35 lfs kernel:  [<c100112d>] ? do_one_initcall+0x44/0x120
Aug 27 23:18:35 lfs kernel:  [<c10517ce>] ? sys_init_module+0xa7/0x1d9
Aug 27 23:18:35 lfs kernel:  [<c138ba4d>] ? syscall_call+0x7/0xb
Aug 27 23:18:35 lfs kernel: Code: e2 05 03 15 c0 65 68 c1 8b 02 25 00
80 00 00 66 85 c0 74 03 8b 52 0c 8b 02 25 00 80 00 00 66 85 c0 74 03
8b 52 0c 80 3a 00 78 04 <0f> 0b eb fe 8b 4a 18 64 a1 e8 5d 5f c1 8b 1c
81 8b 03 3b 43 04
Aug 27 23:18:35 lfs kernel: EIP: [<c108a835>] kfree+0x67/0x96 SS:ESP
0068:cf323f70
Aug 27 23:18:35 lfs kernel: ---[ end trace 00973d9f77f0e389 ]---

The problem is likely caused by free_irq(), but I don't know why and
how to resolve it.