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 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name PX4 nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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/**
 * @file load_mon.cpp
 *
 * @author Jonathan Challinger <jonathan@3drobotics.com>
 * @author Julian Oes <julian@oes.ch
 */

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

#include <px4_config.h>
#include <px4_workqueue.h>
#include <px4_defines.h>

#include <drivers/drv_hrt.h>

#include <systemlib/systemlib.h>
#include <systemlib/err.h>
#include <systemlib/cpuload.h>

#include <uORB/uORB.h>
#include <uORB/topics/cpuload.h>

extern struct system_load_s system_load;


namespace load_mon
{

extern "C" __EXPORT int load_mon_main(int argc, char *argv[]);

// Run it at 1 Hz.
const unsigned LOAD_MON_INTERVAL_US = 1000000;

class LoadMon
{
public:
	LoadMon();
	~LoadMon();

	/* Start the load monitoring
	 *
	 * @return 0 if successfull, -1 on error. */
	int start();

	/* Stop the load monitoring */
	void stop();

	/* Trampoline for the work queue. */
	static void cycle_trampoline(void *arg);

	bool isRunning() { return _taskIsRunning; }

private:
	/* Do a compute and schedule the next cycle. */
	void _cycle();

	/* Do a calculation of the CPU load and publish it. */
	void _compute();

	bool _taskShouldExit;
	bool _taskIsRunning;
	struct work_s _work;

	struct cpuload_s _cpuload;
	orb_advert_t _cpuload_pub;
	hrt_abstime _last_idle_time;
};


LoadMon::LoadMon() :
	_taskShouldExit(false),
	_taskIsRunning(false),
	_work{},
	_cpuload{},
	_cpuload_pub(nullptr),
	_last_idle_time(0)
{}

LoadMon::~LoadMon()
{
	work_cancel(HPWORK, &_work);
	_taskIsRunning = false;
}

int LoadMon::start()
{
	/* Schedule a cycle to start things. */
	return work_queue(HPWORK, &_work, (worker_t)&LoadMon::cycle_trampoline, this, 0);
}

void LoadMon::stop()
{
	_taskShouldExit = true;
}

void
LoadMon::cycle_trampoline(void *arg)
{
	LoadMon *dev = reinterpret_cast<LoadMon *>(arg);

	dev->_cycle();
}

void LoadMon::_cycle()
{
	_taskIsRunning = true;

	_compute();

	if (!_taskShouldExit) {
		work_queue(HPWORK, &_work, (worker_t)&LoadMon::cycle_trampoline, this,
			   USEC2TICK(LOAD_MON_INTERVAL_US));
	}
}

void LoadMon::_compute()
{
	if (_last_idle_time == 0) {
		/* Just get the time in the first iteration */
		_last_idle_time = system_load.tasks[0].total_runtime;
		return;
	}

	/* compute system load */
	const hrt_abstime interval_idletime = system_load.tasks[0].total_runtime - _last_idle_time;
	_last_idle_time = system_load.tasks[0].total_runtime;

	_cpuload.timestamp = hrt_absolute_time();
	_cpuload.load = 1.0f - (float)interval_idletime / (float)LOAD_MON_INTERVAL_US;

	if (_cpuload_pub == nullptr) {
		_cpuload_pub = orb_advertise(ORB_ID(cpuload), &_cpuload);

	} else {
		orb_publish(ORB_ID(cpuload), _cpuload_pub, &_cpuload);
	}
}



/**
 * Print the correct usage.
 */
static void usage(const char *reason);

static void
usage(const char *reason)
{
	if (reason) {
		PX4_ERR("%s", reason);
	}

	PX4_INFO("usage: load_mon {start|stop|status}");
}


static LoadMon *load_mon = nullptr;

/**
 * The daemon app only briefly exists to start
 * the background job. The stack size assigned in the
 * Makefile does only apply to this management task.
 *
 * The actual stack size should be set in the call
 * to task_create().
 */
int load_mon_main(int argc, char *argv[])
{
	if (argc < 2) {
		usage("missing command");
		return 1;
	}

	if (!strcmp(argv[1], "start")) {

		if (load_mon != nullptr && load_mon->isRunning()) {
			PX4_WARN("already running");
			/* this is not an error */
			return 0;
		}

		load_mon = new LoadMon();

		// Check if alloc worked.
		if (load_mon == nullptr) {
			PX4_ERR("alloc failed");
			return -1;
		}

		int ret = load_mon->start();

		if (ret != 0) {
			PX4_ERR("start failed");
		}

		return 0;
	}

	if (!strcmp(argv[1], "stop")) {

		if (load_mon == nullptr || load_mon->isRunning()) {
			PX4_WARN("not running");
			/* this is not an error */
			return 0;
		}

		load_mon->stop();

		// Wait for task to die
		int i = 0;

		do {
			/* wait up to 3s */
			usleep(100000);

		} while (load_mon->isRunning() && ++i < 30);

		delete load_mon;
		load_mon = nullptr;

		return 0;
	}

	if (!strcmp(argv[1], "status")) {
		if (load_mon != nullptr && load_mon->isRunning()) {
			PX4_INFO("running");

		} else {
			PX4_INFO("not running\n");
		}

		return 0;
	}

	usage("unrecognized command");
	return 1;
}

} // namespace load_mon