push_button irq handler question

This code works fine even with such delay in the handler. Without this delay I noticed only quick flash on the corresponding led.

/*
 * "Hello World" example.
 *
 * This example prints 'Hello from Nios II' to the STDOUT stream. It runs on
 * the Nios II 'standard', 'full_featured', 'fast', and 'low_cost' example
 * designs. It runs with or without the MicroC/OS-II RTOS and requires a STDOUT
 * device in your system's hardware.
 * The memory footprint of this hosted application is ~69 kbytes by default
 * using the standard reference design.
 *
 * For a reduced footprint version of this template, and an explanation of how
 * to reduce the memory footprint for a given application, see the
 * "small_hello_world" template.
 *
 */
# include <stdio.h># include "system.h"# include "alt_types.h"# include "sys/alt_irq.h"# include "altera_avalon_pio_regs.h"
//#include <unistd.h>
/* A variable to hold the value of the button pio edge capture register. */
volatile int edge_capture;
/* button IRQ function */
static void handle_button_interrupts(void* context, alt_u32 id)
{
    int delay;
    
    IOWR_ALTERA_AVALON_PIO_DATA(LED_PIO_BASE, ~IORD_ALTERA_AVALON_PIO_EDGE_CAP(BUTTON_PIO_BASE));
    IOWR_ALTERA_AVALON_PIO_EDGE_CAP(BUTTON_PIO_BASE, 0);
    delay=0x1;
    while (delay<1)
        {
            delay++;
        }
}
/* Initialize the button_pio. */
static void init_button_pio()
{
    /* Recast the edge_capture pointer to match the alt_irq_register() function
     * prototype. */
    void* edge_capture_ptr = (void*) &edge_capture;
    /* Enable all 4 button interrupts. */
    IOWR_ALTERA_AVALON_PIO_IRQ_MASK(BUTTON_PIO_BASE, 0xf);
    /* Reset the edge capture register. */
    IOWR_ALTERA_AVALON_PIO_EDGE_CAP(BUTTON_PIO_BASE, 0x0);
    /* Register the interrupt handler. */
    alt_irq_register( BUTTON_PIO_IRQ, edge_capture_ptr,
                      handle_button_interrupts );
}
int main()
{
    printf("Hello from Nios II!\n");
    init_button_pio();
    IOWR_ALTERA_AVALON_PIO_DATA(LED_PIO_BASE, 0xf);
    while (1);
    return 0;
}