Interrupt with push button on P2.1 not working.

Hi

I bought a MSP430f5529LP launchpad and tried to test onboard components by writing a simple code to read push button on P2.1 as interrupt but it does not seem to work.

Is there any other register I need to enable or any other intrinsic function to be used to enable interrupt?

#include <msp430.h>

#define DELAY() \
        i = 10000;    \
        do i--;        \
        while(i != 0)
/*
 * main.c
 */
 int main(void) {
    WDTCTL = WDTPW | WDTHOLD;    // Stop watchdog timer

    P1DIR |= BIT0;
    P4DIR |= BIT7;

    P2DIR &= ~BIT1;
    P2REN |= BIT1;
    P2OUT |= BIT1;
    P2IE |= BIT1;
    P2IFG &= ~BIT1;

    __enable_interrupt();    //Enable all interrupts.
    //_BIS_SR(LPM4_bits + GIE); // Enter LPM4 w/interrupt

    while(1)
    {
        unsigned volatile long i;
        P1OUT ^= BIT0; //toggle P1.0
        DELAY();
    }
}
#pragma vector = PORT1_VECTOR
__interrupt void port_1(void)
{
        P4OUT |= BIT7;    //Glow P4.7 on interrupt.
        P2IFG &= ~BIT1;
}

Now in the above code when push button on P2.1 is pressed the LED on P4.7 should glow, but it does not.

Kindly advise.