Thread scheduling C
- by MRP
include <pthread.h>
include <stdio.h>
include <stdlib.h>
#define NUM_THREADS 4
#define TCOUNT 5
#define COUNT_LIMIT 13
int done = 0;
int count = 0;
int thread_ids[4] = {0,1,2,3};
int thread_runtime[4] = {0,5,4,1};
pthread_mutex_t count_mutex;
pthread_cond_t count_threshold_cv;
void *inc_count(void *t)
{
int i;
long my_id = (long)t;
long run_time = thread_runtime[my_id];
if (my_id==2 && done ==0) {
for(i=0; i< 5 ; i++) {
if( i==4 ){done =1;}
pthread_mutex_lock(&count_mutex);
count++;
if (count == COUNT_LIMIT) {
pthread_cond_signal(&count_threshold_cv);
printf("inc_count(): thread %ld, count = %d Threshold
reached.\n", my_id, count);
}
printf("inc_count(): thread %ld, count = %d, unlocking mutex\n", my_id, count);
pthread_mutex_unlock(&count_mutex);
}
}
if (my_id==3 && done==1) {
for(i=0; i< 4 ; i++)
{
if(i == 3 ){ done = 2;}
pthread_mutex_lock(&count_mutex);
count++;
if (count == COUNT_LIMIT) {
pthread_cond_signal(&count_threshold_cv);
printf("inc_count(): thread %ld, count = %d Threshold reached.\n", my_id, count);
}
printf("inc_count(): thread %ld, count = %d, unlocking mutex\n", my_id, count);
pthread_mutex_unlock(&count_mutex);
}
}
if (my_id==4&& done == 2)
{
for(i=0; i< 8 ; i++) {
pthread_mutex_lock(&count_mutex);
count++;
if (count == COUNT_LIMIT) {
pthread_cond_signal(&count_threshold_cv);
printf("inc_count(): thread %ld, count = %d Threshold reached.\n",my_id, count);
}
printf("inc_count(): thread %ld, count = %d, unlocking mutex\n", my_id, count);
pthread_mutex_unlock(&count_mutex);
}
}
pthread_exit(NULL);
}
void *watch_count(void *t)
{
long my_id = (long)t;
printf("Starting watch_count(): thread %ld\n", my_id);
pthread_mutex_lock(&count_mutex);
if (count<COUNT_LIMIT) {
pthread_cond_wait(&count_threshold_cv, &count_mutex);
printf("watch_count(): thread %ld Condition signal received.\n", my_id);
count += 125;
printf("watch_count(): thread %ld count now = %d.\n", my_id, count);
}
pthread_mutex_unlock(&count_mutex);
pthread_exit(NULL);
}
int main (int argc, char *argv[])
{
int i, rc;
long t1=1, t2=2, t3=3, t4=4;
pthread_t threads[4];
pthread_attr_t attr;
pthread_mutex_init(&count_mutex, NULL);
pthread_cond_init (&count_threshold_cv, NULL);
pthread_attr_init(&attr);
pthread_attr_setdetachstate(&attr,PTHREAD_CREATE_JOINABLE);
pthread_create(&threads[0], &attr, watch_count, (void *)t1);
pthread_create(&threads[1], &attr, inc_count, (void *)t2);
pthread_create(&threads[2], &attr, inc_count, (void *)t3);
pthread_create(&threads[3], &attr, inc_count, (void *)t4);
for (i=0; i<NUM_THREADS; i++) {
pthread_join(threads[i], NULL);
}
printf ("Main(): Waited on %d threads. Done.\n", NUM_THREADS);
pthread_attr_destroy(&attr);
pthread_mutex_destroy(&count_mutex);
pthread_cond_destroy(&count_threshold_cv);
pthread_exit(NULL);
}
so this code creates 4 threads. thread 1 keeps track of the count value while the other 3 increment the count value. the run time is the number of times the thread will increment the count value. I have a done value that allows the first thread to increment the count value first until its run time is up.. so its like a First Come First Serve.
my question is, is there a better way of implementing this? I have read about SCHED_FIFO or SCHED_RR.. I guess I dont know how to implement them into this code or if it can be.
