/*
 * Copyright (C) 2013-2021 Canonical, Ltd.
 * Copyright (C)      2022 Colin Ian King.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 */
#include "stress-ng.h"

#if defined(HAVE_MQUEUE_H)
#include <mqueue.h>
#else
UNEXPECTED
#endif

#if defined(HAVE_SEM_SYSV)
#include <sys/sem.h>
#else
UNEXPECTED
#endif

static const stress_help_t help[] = {
	{ "s N","switch N",	 	"start N workers doing rapid context switches" },
	{ NULL,	"switch-ops N",	 	"stop after N context switch bogo operations" },
	{ NULL, "switch-freq N", 	"set frequency of context switches" },
	{ NULL, "switch-method M",	"mq | pipe | sem-sysv" },
	{ NULL, NULL, 		 NULL }
};

typedef struct {
	const char *name;
	int (*func)(const stress_args_t *args, const uint64_t switch_freq,
		    const uint64_t switch_delay, const uint64_t threshold);
} stress_switch_method_t;

#define THRESH_FREQ	(100)		/* Delay adjustment rate in HZ */

/*
 *  stress_set_switch_freq()
 *	set context switch freq in Hz from given option
 */
static int stress_set_switch_freq(const char *opt)
{
	uint64_t switch_freq;

	switch_freq = stress_get_uint64(opt);
	stress_check_range("switch-freq", switch_freq, 0, STRESS_NANOSECOND);
	return stress_set_setting("switch-freq", TYPE_ID_UINT64, &switch_freq);
}

/*
 *  stress_switch_rate()
 *	report context switch duration
 */
static void stress_switch_rate(
	const stress_args_t *args,
	char *method,
	const double t_start,
	const double t_end,
	uint64_t counter)
{
	pr_inf("%s: (%s) %.2f nanoseconds per context switch (based on parent run time)\n",
		args->name, method,
		((t_end - t_start) * STRESS_NANOSECOND) / (double)counter);
}

/*
 *  stress_switch_delay()
 *	adjustable delay to try and keep switch rate to
 *	a specified frequency
 */
static void stress_switch_delay(
	const stress_args_t *args,
	const uint64_t switch_delay,
	const uint64_t threshold,
	const double t_start,
	uint64_t *delay)
{
	static uint64_t i = 0;

	/*
	 *  Small delays take a while, so skip these
	 */
	if (*delay > 1000)
		shim_nanosleep_uint64(*delay);

	/*
	 *  This is expensive, so only update the
	 *  delay infrequently (at THRESH_FREQ HZ)
	 */
	if (++i >= threshold) {
		double overrun, overrun_by, t;
		const uint64_t counter = get_counter(args);

		i = 0;
		t = t_start + ((double)(counter * switch_delay) / STRESS_NANOSECOND);
		overrun = (stress_time_now() - t) * (double)STRESS_NANOSECOND;
		overrun_by = (double)switch_delay - overrun;

		if (overrun_by < 0.0) {
			/* Massive overrun, skip a delay */
			*delay = 0;
		} else {
			/* Overrun or underrun? */
			*delay = (uint64_t)overrun_by;
			if (*delay > switch_delay) {
				/* Don't delay more than the switch delay */
				*delay = switch_delay;
			}
		}
	}
}

/*
 *  stress_switch_pipe
 *	stress by heavy context switching using pipe
 *	synchronization method
 */
static int stress_switch_pipe(
	const stress_args_t *args,
	const uint64_t switch_freq,
	const uint64_t switch_delay,
	const uint64_t threshold)
{
	pid_t pid;
	int pipefds[2];
	size_t buf_size;

	(void)memset(pipefds, 0, sizeof(pipefds));
#if defined(HAVE_PIPE2) &&	\
    defined(O_DIRECT)
	if (pipe2(pipefds, O_DIRECT) < 0) {
		/*
		 *  Fallback to pipe if pipe2 fails
		 */
		if (pipe(pipefds) < 0) {
			pr_fail("%s: pipe failed, errno=%d (%s)\n",
				args->name, errno, strerror(errno));
			return EXIT_FAILURE;
		}
	}
	buf_size = 1;
#else
	if (pipe(pipefds) < 0) {
		pr_fail("%s: pipe failed, errno=%d (%s)\n",
			args->name, errno, strerror(errno));
		return EXIT_FAILURE;
	}
	buf_size = args->page_size;
#endif

#if defined(F_SETPIPE_SZ)
	if (fcntl(pipefds[0], F_SETPIPE_SZ, buf_size) < 0) {
		pr_dbg("%s: could not force pipe size to 1 page, "
			"errno = %d (%s)\n",
			args->name, errno, strerror(errno));
	}
	if (fcntl(pipefds[1], F_SETPIPE_SZ, buf_size) < 0) {
		pr_dbg("%s: could not force pipe size to 1 page, "
			"errno = %d (%s)\n",
			args->name, errno, strerror(errno));
	}
#endif

	stress_set_proc_state(args->name, STRESS_STATE_RUN);
again:
	pid = fork();
	if (pid < 0) {
		if (stress_redo_fork(errno))
			goto again;
		(void)close(pipefds[0]);
		(void)close(pipefds[1]);
		if (!keep_stressing(args))
			goto finish;
		pr_fail("%s: fork failed, errno=%d (%s)\n",
			args->name, errno, strerror(errno));
		return EXIT_FAILURE;
	} else if (pid == 0) {
		char buf[buf_size];

		(void)setpgid(0, g_pgrp);
		stress_parent_died_alarm();
		(void)sched_settings_apply(true);

		(void)close(pipefds[1]);

		while (keep_stressing_flag()) {
			ssize_t ret;

			ret = read(pipefds[0], buf, sizeof(buf));
			if (ret <= 0) {
				if (errno == 0)	/* ret == 0 case */
					break;
				if ((errno == EAGAIN) || (errno == EINTR))
					continue;
				if (errno == EPIPE)
					break;
				pr_fail("%s: read failed, errno=%d (%s)\n",
					args->name, errno, strerror(errno));
				break;
			}
		}
		(void)close(pipefds[0]);
		_exit(EXIT_SUCCESS);
	} else {
		char buf[buf_size];
		int status;
		double t_start;
		uint64_t delay = switch_delay;

		/* Parent */
		(void)setpgid(pid, g_pgrp);
		(void)close(pipefds[0]);
		(void)memset(buf, '_', buf_size);

		t_start = stress_time_now();
		do {
			ssize_t ret;

			inc_counter(args);

			ret = write(pipefds[1], buf, sizeof(buf));
			if (ret <= 0) {
				if ((errno == EAGAIN) || (errno == EINTR))
					continue;
				if (errno == EPIPE)
					break;
				if (errno) {
					pr_fail("%s: write failed, errno=%d (%s)\n",
						args->name, errno, strerror(errno));
					break;
				}
				continue;
			}

			if (switch_freq)
				stress_switch_delay(args, switch_delay, threshold, t_start, &delay);
		} while (keep_stressing(args));

		stress_switch_rate(args, "pipe", t_start, stress_time_now(), get_counter(args));

		(void)close(pipefds[0]);

		(void)kill(pid, SIGKILL);
		(void)shim_waitpid(pid, &status, 0);
	}
finish:
	stress_set_proc_state(args->name, STRESS_STATE_DEINIT);

	return EXIT_SUCCESS;
}

#if defined(HAVE_SEM_SYSV)
/*
 *  stress_switch_sem_sysv
 *	stress by heavy context switching using semaphore
 *	synchronization method
 */
static int stress_switch_sem_sysv(
	const stress_args_t *args,
	const uint64_t switch_freq,
	const uint64_t switch_delay,
	const uint64_t threshold)
{
	pid_t pid;
	int sem_id;
	int i;

	for (i = 0; i < 100; i++) {
		key_t key_id = (key_t)stress_mwc16();

		sem_id = semget(key_id, 1, IPC_CREAT | S_IRUSR | S_IWUSR);
		if (sem_id >= 0)
			break;
	}
	if (sem_id < 0) {
		pr_err("%s: semaphore init (SYSV) failed: errno=%d (%s)\n",
			args->name, errno, strerror(errno));
                return EXIT_FAILURE;
        }

	stress_set_proc_state(args->name, STRESS_STATE_RUN);
again:
	pid = fork();
	if (pid < 0) {
		if (stress_redo_fork(errno))
			goto again;
		if (!keep_stressing(args))
			goto finish;
		pr_fail("%s: fork failed, errno=%d (%s)\n",
			args->name, errno, strerror(errno));
		return EXIT_FAILURE;
	} else if (pid == 0) {
		(void)setpgid(0, g_pgrp);
		stress_parent_died_alarm();
		(void)sched_settings_apply(true);

		while (keep_stressing_flag()) {
			struct sembuf sem;

			sem.sem_num = 0;
			sem.sem_op = -1;
			sem.sem_flg = SEM_UNDO;

			if (semop(sem_id, &sem, 1) < 0)
				break;

			sem.sem_num = 0;
			sem.sem_op = 1;
			sem.sem_flg = SEM_UNDO;

			if (semop(sem_id, &sem, 1) < 0)
				break;
		}
		_exit(EXIT_SUCCESS);
	} else {
		int status;
		double t_start;
		uint64_t delay = switch_delay;
		struct sembuf sem;

		/* Parent */
		(void)setpgid(pid, g_pgrp);

		t_start = stress_time_now();
		do {
			inc_counter(args);

			sem.sem_num = 0;
			sem.sem_op = 1;
			sem.sem_flg = SEM_UNDO;

			if (semop(sem_id, &sem, 1) < 0)
				break;

			if (switch_freq)
				stress_switch_delay(args, switch_delay, threshold, t_start, &delay);

			if (!keep_stressing(args))
				break;
			sem.sem_num = 0;
			sem.sem_op = -1;
			sem.sem_flg = SEM_UNDO;

			if (semop(sem_id, &sem, 1) < 0)
				break;
		} while (keep_stressing(args));

		stress_switch_rate(args, "sem-sysv", t_start, stress_time_now(), 2 * get_counter(args));

		(void)kill(pid, SIGKILL);
		(void)shim_waitpid(pid, &status, 0);
	}
finish:
	stress_set_proc_state(args->name, STRESS_STATE_DEINIT);

	semctl(sem_id, 0, IPC_RMID);

	return EXIT_SUCCESS;
}
#endif

#if defined(HAVE_MQUEUE_H) &&   \
    defined(HAVE_LIB_RT) &&     \
    defined(HAVE_MQ_POSIX)
/*
 *  stress_switch_mq
 *	stress by heavy context switching using message queue
 */
static int stress_switch_mq(
	const stress_args_t *args,
	const uint64_t switch_freq,
	const uint64_t switch_delay,
	const uint64_t threshold)
{
	typedef struct {
		uint64_t        value;
	} stress_msg_t;

	pid_t pid;
	mqd_t mq;
	char mq_name[64];
	struct mq_attr attr;
	stress_msg_t msg;

	(void)snprintf(mq_name, sizeof(mq_name), "/%s-%" PRIdMAX "-%" PRIu32,
			args->name, (intmax_t)args->pid, args->instance);
	attr.mq_flags = 0;
	attr.mq_maxmsg = 1;
	attr.mq_msgsize = sizeof(stress_msg_t);
	attr.mq_curmsgs = 0;
	mq = mq_open(mq_name, O_CREAT | O_RDWR, S_IRUSR | S_IWUSR, &attr);
	if (mq < 0) {
		pr_err("%s: message queue open failed: errno=%d (%s)\n",
			args->name, errno, strerror(errno));
                return EXIT_FAILURE;
	}

	(void)memset(&msg, 0, sizeof(msg));
	stress_set_proc_state(args->name, STRESS_STATE_RUN);
again:
	pid = fork();
	if (pid < 0) {
		if (stress_redo_fork(errno))
			goto again;
		if (!keep_stressing(args))
			goto finish;
		pr_fail("%s: fork failed, errno=%d (%s)\n",
			args->name, errno, strerror(errno));
		return EXIT_FAILURE;
	} else if (pid == 0) {
		(void)setpgid(0, g_pgrp);
		stress_parent_died_alarm();
		(void)sched_settings_apply(true);

		while (keep_stressing_flag()) {
			msg.value++;
			if (mq_send(mq, (char *)&msg, sizeof(msg), 0) < 0)
				break;
		}
		_exit(EXIT_SUCCESS);
	} else {
		int status;
		double t_start;
		uint64_t delay = switch_delay;

		/* Parent */
		(void)setpgid(pid, g_pgrp);

		t_start = stress_time_now();
		do {
			inc_counter(args);
			unsigned int prio;

			if (mq_receive(mq, (char *)&msg, sizeof(msg), &prio) < 0)
				break;

			if (switch_freq)
				stress_switch_delay(args, switch_delay, threshold, t_start, &delay);
		} while (keep_stressing(args));

		stress_switch_rate(args, "mq", t_start, stress_time_now(), get_counter(args));

		(void)kill(pid, SIGKILL);
		(void)shim_waitpid(pid, &status, 0);
	}
finish:
	stress_set_proc_state(args->name, STRESS_STATE_DEINIT);

	(void)mq_close(mq);
	(void)mq_unlink(mq_name);

	return EXIT_SUCCESS;
}
#endif

static stress_switch_method_t stress_switch_methods[] = {
#if defined(HAVE_MQUEUE_H) &&   \
    defined(HAVE_LIB_RT) &&     \
    defined(HAVE_MQ_POSIX)
	{ "mq",		stress_switch_mq },
#endif
	{ "pipe",	stress_switch_pipe },
#if defined(HAVE_SEM_SYSV)
	{ "sem-sysv",	stress_switch_sem_sysv },
#endif
	{ NULL,		NULL },
};

/*
 *  stress_set_switch_method()
 *	set the default switch method
 */
static int stress_set_switch_method(const char *name)
{
	stress_switch_method_t *info;

	for (info = stress_switch_methods; info->name; info++) {
		if (!strcmp(info->name, name)) {
			stress_set_setting("switch-method", TYPE_ID_UINTPTR_T, &info);
			return 0;
		}
	}

	(void)fprintf(stderr, "switch-method must be one of:");
	for (info = stress_switch_methods; info->name; info++) {
		(void)fprintf(stderr, " %s", info->name);
	}
	(void)fprintf(stderr, "\n");

	return -1;
}

/*
 *  stress_switch
 *	stress by heavy context switching
 */
static int stress_switch(const stress_args_t *args)
{
	uint64_t switch_freq = 0, switch_delay, threshold;

	stress_switch_method_t *switch_method;

	(void)stress_get_setting("switch-freq", &switch_freq);
	(void)stress_get_setting("switch-method", (void *)&switch_method);

	switch_delay = (switch_freq == 0) ? 0 : STRESS_NANOSECOND / switch_freq;
	threshold = switch_freq / THRESH_FREQ;

	return switch_method->func(args, switch_freq, switch_delay, threshold);
}

static void stress_switch_set_default(void)
{
	stress_set_switch_method("pipe");
}

static const stress_opt_set_func_t opt_set_funcs[] = {
	{ OPT_switch_freq,	stress_set_switch_freq },
	{ OPT_switch_method,	stress_set_switch_method },
	{ 0,			NULL }
};

stressor_info_t stress_switch_info = {
	.stressor = stress_switch,
	.class = CLASS_SCHEDULER | CLASS_OS,
	.opt_set_funcs = opt_set_funcs,
	.set_default = stress_switch_set_default,
	.verify = VERIFY_ALWAYS,
	.help = help
};