clkhandler.c

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/* clkhandler.c - clkhandler */

#include <xinu.h>

/*-----------------------------------------------------------------------
 * clkhandler - high level clock interrupt handler
 *-----------------------------------------------------------------------
 */
void    clkhandler()
{

    
    volatile struct am335x_timer1ms *csrptr =
            (struct am335x_timer1ms *)0x44E31000;
            /* Set csrptr to address of timer CSR       */

    /* If there is no interrupt, return */

    if((csrptr->tisr & AM335X_TIMER1MS_TISR_OVF_IT_FLAG) == 0) {
        return;
    }

    /* Acknowledge the interrupt */

    csrptr->tisr = AM335X_TIMER1MS_TISR_OVF_IT_FLAG;

    /* Increment 1000ms counter */

    count1000++;

    /* After 1 sec, increment clktime */

    if(count1000 >= 1000) {
        clktime++;
        count1000 = 0;
    }

    /* check if sleep queue is empty */

    if(!isempty(sleepq)) {

        /* sleepq nonempty, decrement the key of */
        /* topmost process on sleepq         */

        if((--queuetab[firstid(sleepq)].qkey) == 0) {

            wakeup();
        }
    }

    /* Decrement the preemption counter */
    /* Reschedule if necessary      */

    if((--preempt) == 0) {
        preempt = QUANTUM;
        resched();
    }
}