#include <stdio.h>
#include <assert.h>
#include <limits.h>

#include <fcntl.h>
#include <sched.h>
#include <pthread.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>

#include <asm/param.h>


/*
 * valid policy include SCHED_FIFO, SCHED_RR, SCHED_OTHER
 */
int change_sched(int policy, int priority)
{
	struct sched_param sched_param;
	sched_param.sched_priority = priority;
	return sched_setscheduler(0, policy, &sched_param);
}

void check_realtime(char *prompt)
{
        int sched_policy;
        struct sched_param sched_param;

        sched_policy = sched_getscheduler(0);
        switch (sched_policy) {
                case SCHED_FIFO:
                        printf("%s: sched policy is SCHED_FIFO.\n", prompt);
                        break;
                case SCHED_RR:
                        printf("%s: sched policy is SCHED_RR.\n", prompt);
                        break;
                case SCHED_OTHER:
                        printf("%s: sched policy is SCHED_OTHER.\n", prompt);
                        break;
                default:
                        printf("error!\n");
                        exit(-1);
        }

        sched_getparam(0, &sched_param);
        printf("%s: sched priority is %d in the range [%d, %d]\n",
			prompt,
                        sched_param.sched_priority,
                        sched_get_priority_min(sched_policy),
                        sched_get_priority_max(sched_policy));
}

void *SlaveRun (void *t)
{
	printf("slave: run\n");
	check_realtime("slave");
	return 0;
}

void check_ret(int flag, char *msg)
{
	if (flag)
		printf("%s succeeded\n", msg);
	else
		printf("%s failed\n", msg);
}

int main(int argc, char *argv[])
{
	int ret;
	pthread_t thread;
	pthread_attr_t attr;
	struct sched_param sched_param;

	check_realtime("master");
	ret = change_sched(SCHED_FIFO, 50);
	if (ret) {
		printf("Change to SCHED_FIFO at priority 50 faied.\n");
	} else {
		printf("Change to SCHED_FIFO at priority 50 succeeded.\n");
		check_realtime("master");
	}

	{
	printf("create a thread with priority 60 ...\n");
	assert(!pthread_attr_init (&attr));
	assert(!pthread_attr_setinheritsched (&attr, PTHREAD_EXPLICIT_SCHED));
	assert(!pthread_attr_setschedpolicy (&attr, SCHED_FIFO));
	// assert(!pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED));

	sched_param.sched_priority = 60;
	assert(!pthread_attr_setschedparam (&attr, &sched_param));

	ret = pthread_create(&thread, &attr, SlaveRun, (void *) 0);
	check_ret(ret==0, "master: creating thread");

	ret = pthread_cancel (thread);
	check_ret(ret==0, "pthread_cancel");

	ret = pthread_join(thread, NULL);
	check_ret(ret==0, "pthread_join");
	}

	{
	printf("create a thread with priority 40 ...\n");
	assert(!pthread_attr_init (&attr));
	assert(!pthread_attr_setinheritsched (&attr, PTHREAD_EXPLICIT_SCHED));
	assert(!pthread_attr_setschedpolicy (&attr, SCHED_FIFO));
	// assert(!pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED));

	sched_param.sched_priority = 40;
	assert(!pthread_attr_setschedparam (&attr, &sched_param));

	ret = pthread_create(&thread, &attr, SlaveRun, (void *) 0);
	check_ret(ret==0, "master: creating thread");

	ret = pthread_cancel (thread);
	check_ret(ret==0, "pthread_cancel");

	ret = pthread_join(thread, NULL);
	check_ret(ret==0, "pthread_join");
	}

	return 0;
}