[PLUG] Asynchronous Notification

[paras]

Hi all,
I am working on linux kernel-2.6.20.
I write one kernel module for GPIO.
In my module, I am generating an interrupt when the status of GPIO pin (e.g
GPIP 3) changes. its works properly.
Then I am using Asynchronous Notification to get notification of interrupt
in my user space process.
For that I used fasync method. kill_fasync() called in interrupt handler of
gpio.
According to Linux Device Driver Book, kill_fasync is used to signal the
interested processes when data arrives.

So my problem is, I am changing the status of gpio pin twice, according to
documentation I will get SIGIO signal twice.
But It don't happen so, I got SIGIO only once.
Please any one tell me why this happen?

Thanks in Advance