suspend.c

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#include <xinu.h>

syscall suspend(pid32 pid)
{
    intmask mask;          /* Saved interrupt mask      */
    struct procent *prptr; /* Ptr to process's table entry  */
    pri16 prio;            /* Priority to return        */

    mask = disable();
    if (isbadpid(pid) || (pid == NULLPROC))
    {
        restore(mask);
        return SYSERR;
    }

    /* Only suspend a process that is current or ready */

    prptr = &proctab[pid];
    if ((prptr->prstate != PR_CURR) && (prptr->prstate != PR_READY))
    {
        restore(mask);
        return SYSERR;
    }
    if (prptr->prstate == PR_READY)
    {
        getitem(pid); /* Remove a ready process */
                      /*   from the ready list  */
        prptr->prstate = PR_SUSP;
    }
    else
    {
        prptr->prstate = PR_SUSP; /* Mark the current process   */
        resched();                /*   suspended and resched.   */
    }
    prio = prptr->prprio;
    restore(mask);
    return prio;
}