scheduler2.c

/* Alternate logic scheduler */
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include <time.h>
#include "processDef.h"
#include "queueDef.h"

extern pthread_mutex_t mutex;
extern pthread_cond_t turn_cond;
extern int tt, turn, qt, st, switchCount, totalRemt;
extern QL *front, *rear;

typedef struct
{
    Pr *currentProcess;
    Pr *processArray;
    int numProcesses;
} ThreadArgs;

void enQueue(QL **front, QL **rear, Pr val);
Pr deQueue(QL **front);

void *queueMaintainer(Pr *P, int n)
{
    int i;

    for (i = 0; i < n; i++)
    {
        if (tt == P[i].at && P[i].enqueued == 0 && P[i].remt > 0)
        {
            enQueue(&front, &rear, P[i]);
            P[i].enqueued = 1; // Marking as enqueued
        }
    }
}

void advanceTimeDeadlockAvoider(Pr *processArray, int n)
{
    int i, j;
    for (i = 0; i < n; i++)
    {
        if (processArray[i].cpu == 0 && processArray[i].at > tt)
        {
            switchCount += (processArray[i].at - tt);
            for (j = 0; j < (processArray[i].at - tt); j++)
                printf(" X ");

            tt = processArray[i].at;
            turn = processArray[i].index;
            pthread_cond_signal(&turn_cond);
            break;
        }
    }
}

void *scheduler2(void *threadargs)
{
    ThreadArgs *args = (ThreadArgs *)threadargs;
    Pr *P = args->currentProcess;
    Pr *allProcesses = args->processArray;
    int n = args->numProcesses;

    pthread_t sid;
    Pr temp;
    int timeSlice = 0, i;
    struct timespec ts;
    ts.tv_sec = 1;
    ts.tv_nsec = 0;

    while (1)
    {
        pthread_mutex_lock(&mutex);

        while (turn != P->index)
        {
            pthread_cond_wait(&turn_cond, &mutex);
        }

        if (P->remt > 0)
        {
            sid = pthread_self();
            P->cpu = 1;

            while (timeSlice < qt && P->remt > 0)
            {
                if (P->remt == P->bt)
                    P->start = tt;
                tt++;
                printf(" %s ", P->name);
                fflush(stdout);
                P->remt--;
                totalRemt--;
                timeSlice++;
                queueMaintainer(allProcesses, n);
                nanosleep(&ts, NULL);
            }

            if (P->remt > 0)
            {
                enQueue(&front, &rear, *P);
            }
            if (P->remt == 0)
                P->ct = tt;

            for (i = 1; i <= st; i++)
            {
                tt++;
                switchCount++;
                queueMaintainer(allProcesses, n);
                if (totalRemt > 0)
                {
                    printf(" X ");
                    fflush(stdout);
                }
            }

            Pr temp = deQueue(&front);
            if (temp.index != -1)
            {
                turn = temp.index;
            }
            else
            {
                advanceTimeDeadlockAvoider(allProcesses, n);
            }
            pthread_cond_signal(&turn_cond);
        }

        pthread_mutex_unlock(&mutex);
        timeSlice = 0;

        if (P->remt == 0)
        {
            free(args);
            pthread_exit((void *)(long)sid);
        }
    }
}