#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <errno.h>
#include <signal.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/resource.h>
#include <memory.h>

#define THREAD_NUM 5

static void printprio(const char *pfx)
{
	int prio;
	pid_t tid = syscall(SYS_gettid);
	pid_t pid = getpid();
	prio = getpriority(PRIO_PROCESS, tid);
	printf("%sTID:%d getpriority:%d\n", pfx, tid, prio);
	prio = getpriority(PRIO_PROCESS, pid);
	printf("%sPID:%d getpriority:%d\n", pfx, pid, prio);
}

int threadno;

static void* threadfunc(void *dummy)
{
	sleep(1); /* wait for parent to setpriority */
	setpriority(3 /*PRIO_THREAD*/, syscall(SYS_gettid), -(++threadno));
	setpriority(PRIO_PROCESS, syscall(SYS_gettid), -(++threadno));
	printprio("THREAD CHILD: ");
	pthread_exit(0);
}

int main()
{
	pid_t pid = fork();
	if (pid) {
		/* parent */
		int status;
		printf("start test program\n");
		sleep(1); /* wait for threads to start in child */
		printf("setpriority(PRIO_PROCESS, %d, -10)\n", pid);
		if (setpriority(PRIO_PROCESS, pid, -10) < 0) {
			perror("setpriority PRIO_PROCESS");
			exit(1);
		}
		wait(&status);
	} else { 
		/* child */
		int i;
		pthread_t thread_id[THREAD_NUM];

		printprio("CHILD1: ");
		for (i = 1; i < THREAD_NUM; i++) {
			usleep(30*1000);
			pthread_create(&thread_id[i], NULL, &threadfunc, NULL);
		}

		usleep(30*1000);
		sleep(1); /* wait for parent to setpriority */
		printprio("CHILD2: ");

		for (i = 1; i < THREAD_NUM; i++) {
			pthread_join(thread_id[i], NULL);
			printf("Joined!\n");
		}
	}
	return 0;
}