Programming external interrupt 0

i am programming interrupt 0 using 8051
my task is.. explained in the circuit diagram as follows

when ever till the push button pressed the led should goes low which is connected at P2.1

but the problem i am facing is if long press the button the led toggles quickly and repeatedly... but i want that till the button is pressed the led should be off

here is my code

CODE/

#include<reg51.h>
sbit a=P2^1; // for led
void ext(void) interrupt 0
{
a=0;

}
void main()
{
IE=0x81; // using external 0 interrupt

while(1)
{
a=1;
}
}

you need to put a wait condition in ISR till the switch is released e.g.

void ext(void) interrupt 0
{
    a=0;
    while (!P3^2); //wait for pin to go high
}