/* based_mt_task.c -- A basic multi-threaded real-time task skeleton. 
 *
 * This (by itself useless) task demos how to setup a multi-threaded LITMUS^RT
 * real-time task. Familiarity with the single threaded example (base_task.c)
 * is assumed.
 *
 * Currently, liblitmus still lacks automated support for real-time
 * tasks, but internaly it is thread-safe, and thus can be used together
 * with pthreads.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* Include gettid() */
#include <sys/types.h>

/* Include threading support. */
#include <pthread.h>

/* Include the LITMUS^RT API.*/
#include "litmus.h"

#define PERIOD            100
#define RELATIVE_DEADLINE 100
#define EXEC_COST         10

#define NS_PER_MS         1e6

/* Let's create 10 threads in the example, 
 * for a total utilization of 1.
 */
#define NUM_THREADS      10 

/* The information passed to each thread. Could be anything. */
struct thread_context {
	int id;
};

/* The real-time thread program. Doesn't have to be the same for
 * all threads. Here, we only have one that will invoke job().
 */
void* rt_thread(void *tcontext);

/* Declare the periodically invoked job. 
 * Returns 1 -> task should exit.
 *         0 -> task should continue.
 */
int job(void);


/* Catch errors.
 */
#define CALL( exp ) do { \
		int ret; \
		ret = exp; \
		if (ret != 0) \
			fprintf(stderr, "%s failed: %m\n", #exp);\
		else \
			fprintf(stderr, "%s ok.\n", #exp); \
	} while (0)


/* Basic setup is the same as in the single-threaded example. However, 
 * we do some thread initiliazation first before invoking the job.
 */
int main(int argc, char** argv)
{
	int i;
	struct thread_context ctx[NUM_THREADS];
	pthread_t             task[NUM_THREADS];

	/* The task is in background mode upon startup. */		


	/*****
	 * 1) Command line paramter parsing would be done here.
	 */


       
	/*****
	 * 2) Work environment (e.g., global data structures, file data, etc.) would
	 *    be setup here.
	 */



	/*****
	 * 3) Initialize LITMUS^RT.
	 *    Task parameters will be specified per thread.
	 */
	init_litmus();


	/***** 
	 * 4) Launch threads.
	 */
	for (i = 0; i < NUM_THREADS; i++) {
		ctx[i].id = i;
		pthread_create(task + i, NULL, rt_thread, (void *) (ctx + i));
	}

	
	/*****
	 * 5) Wait for RT threads to terminate.
	 */
	for (i = 0; i < NUM_THREADS; i++)
		pthread_join(task[i], NULL);
	

	/***** 
	 * 6) Clean up, maybe print results and stats, and exit.
	 */
	return 0;
}



/* A real-time thread is very similar to the main function of a single-threaded
 * real-time app. Notice, that init_rt_thread() is called to initialized per-thread
 * data structures of the LITMUS^RT user space libary.
 */
void* rt_thread(void *tcontext)
{
	int do_exit;
	struct thread_context *ctx = (struct thread_context *) tcontext;
	struct rt_task param;

	/* Set up task parameters */
	memset(&param, 0, sizeof(param));
	param.exec_cost = EXEC_COST * NS_PER_MS;
	param.period = PERIOD * NS_PER_MS;
	param.relative_deadline = RELATIVE_DEADLINE * NS_PER_MS;
	param.cls = RT_CLASS_SOFT;
	param.budget_policy = NO_ENFORCEMENT;

	/* Make presence visible. */
	printf("RT Thread %d active.\n", ctx->id);

	/*****
	 * 1) Initialize real-time settings.
	 */
	CALL( init_rt_thread() );

	/* To specify a partition, do
	 *
	 * param.cpu = CPU;
	 * be_migrate_to(CPU);
	 *
	 * where CPU ranges from 0 to "Number of CPUs" - 1 before calling
	 * set_rt_task_param().
	 */
	CALL( set_rt_task_param(gettid(), &param) );

	/*****
	 * 2) Transition to real-time mode.
	 */
	CALL( task_mode(LITMUS_RT_TASK) );

	/* The task is now executing as a real-time task if the call didn't fail. 
	 */



	/*****
	 * 3) Invoke real-time jobs.
	 */
	do {
		/* Wait until the next job is released. */
		sleep_next_period();
		/* Invoke job. */
		do_exit = job();		
	} while (!do_exit);


	
	/*****
	 * 4) Transition to background mode.
	 */
	CALL( task_mode(BACKGROUND_TASK) );


	return NULL;
}



int job(void) 
{
	/* Do real-time calculation. */

	/* Don't exit. */
	return 0;
}