[PATCH V2 3/3] testsuite/latmus: introduce latmus benchmark

[hongzha1 <hongzhan.chen@intel.com>]

Measure response time to GPIO events sent by a remote Zephyr-based
latency monitor (latmon). This monitor collects then sends the latency
data over a network connection to the latmus front-end which displays
the results received:

[Linux device under test running latmus]  <--+
                                             |
        ^                 | (GPIO ack)       |
        |                 |                  |  TCP/IP network connection
        |                 |                  |  (control & data samples)
        | (GPIO pulse)    v                  |
                                             |
[Zephyr-based device running latmon]      <--+

The generic latency monitor code running the measurement loop is
available from the zephyr/ directory. This support comes with a Zephyr
device tree patch for enabling this monitor on NXP's FRDM-K64F
development board.

Signed-off-by: hongzha1 <hongzhan.chen@intel.com>
---
 configure.ac                 |    1 +
 include/rtdm/uapi/testing.h  |   16 +
 testsuite/Makefile.am        |    4 +-
 testsuite/latmus/Makefile.am |   18 +
 testsuite/latmus/latmus.c    | 1446 ++++++++++++++++++++++++++++++++++
 5 files changed, 1484 insertions(+), 1 deletion(-)
 create mode 100644 testsuite/latmus/Makefile.am
 create mode 100644 testsuite/latmus/latmus.c

diff --git a/configure.ac b/configure.ac
index bd5fd5ba9..e8516e103 100644
--- a/configure.ac
+++ b/configure.ac
@@ -954,6 +954,7 @@ AC_CONFIG_FILES([ \
 	lib/trank/Makefile \
 	testsuite/Makefile \
 	testsuite/latency/Makefile \
+	testsuite/latmus/Makefile \
 	testsuite/switchtest/Makefile \
 	testsuite/gpiotest/Makefile \
 	testsuite/gpiobench/Makefile \
diff --git a/include/rtdm/uapi/testing.h b/include/rtdm/uapi/testing.h
index b1723b9f8..d7e2707e1 100644
--- a/include/rtdm/uapi/testing.h
+++ b/include/rtdm/uapi/testing.h
@@ -256,6 +256,22 @@ struct latmus_result {
 #define RTTST_RTIOC_COBALT_LATIOC_RESET	\
 	_IO(RTIOC_TYPE_TESTING, 0x54)
 
+#define LATMON_NET_PORT 2306
+
+struct latmon_net_request {
+	uint32_t period_usecs;
+	uint32_t histogram_cells;
+} __attribute__((__packed__));
+
+struct latmon_net_data {
+	int32_t sum_lat_hi;
+	int32_t sum_lat_lo;
+	int32_t min_lat;
+	int32_t max_lat;
+	uint32_t overruns;
+	uint32_t samples;
+} __attribute__((__packed__));
+
 /** @} */
 
 #endif /* !_RTDM_UAPI_TESTING_H */
diff --git a/testsuite/Makefile.am b/testsuite/Makefile.am
index 4932f6d33..4baff2f19 100644
--- a/testsuite/Makefile.am
+++ b/testsuite/Makefile.am
@@ -1,10 +1,11 @@
 
-SUBDIRS = latency smokey gpiobench
+SUBDIRS = latency latmus smokey gpiobench
 
 if XENO_COBALT
 SUBDIRS += 		\
 	clocktest	\
 	gpiotest	\
+	latmus		\
 	spitest		\
 	switchtest	\
 	xeno-test
@@ -15,6 +16,7 @@ DIST_SUBDIRS =		\
 	gpiotest	\
 	gpiobench   \
 	latency		\
+	latmus		\
 	smokey		\
 	spitest		\
 	switchtest	\
diff --git a/testsuite/latmus/Makefile.am b/testsuite/latmus/Makefile.am
new file mode 100644
index 000000000..8eab3d740
--- /dev/null
+++ b/testsuite/latmus/Makefile.am
@@ -0,0 +1,18 @@
+testdir = @XENO_TEST_DIR@
+
+CCLD = $(top_srcdir)/scripts/wrap-link.sh $(CC)
+
+test_PROGRAMS = latmus
+
+latmus_SOURCES = latmus.c
+
+latmus_CPPFLAGS = 		\
+	$(XENO_USER_CFLAGS)	\
+	-I$(top_srcdir)/include
+
+latmus_LDFLAGS = @XENO_AUTOINIT_LDFLAGS@ $(XENO_POSIX_WRAPPERS)
+
+latmus_LDADD =			\
+	@XENO_CORE_LDADD@		\
+	@XENO_USER_LDADD@		\
+	-lpthread -lrt -lm
diff --git a/testsuite/latmus/latmus.c b/testsuite/latmus/latmus.c
new file mode 100644
index 000000000..016984444
--- /dev/null
+++ b/testsuite/latmus/latmus.c
@@ -0,0 +1,1446 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Derived from Xenomai Cobalt's latency & autotune utilities
+ * (http://git.xenomai.org/xenomai-3.git/)
+ * Copyright (C) 2014 Gilles Chanteperdrix <gch@xenomai.org>
+ * Copyright (C) 2018-2020 Philippe Gerum  <rpm@xenomai.org>
+ */
+
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <getopt.h>
+#include <netdb.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <signal.h>
+#include <pthread.h>
+#include <semaphore.h>
+#include <limits.h>
+#include <time.h>
+#include <string.h>
+#include <memory.h>
+#include <poll.h>
+#include <signal.h>
+#include <error.h>
+#include <errno.h>
+#include <unistd.h>
+#include <ctype.h>
+#include <sys/ioctl.h>
+#include <arpa/inet.h>
+#include <linux/gpio.h>
+#include <rtdm/testing.h>
+#include <rtdm/gpio.h>
+
+#define COBALT_CPU_OOB      (1 << 0)
+#define COBALT_CPU_ISOL     (1 << 1)
+#define COBALT_CPU_OFFLINE  (1 << 2)
+
+#define ISOLATED_CPU_LIST "/sys/devices/system/cpu/isolated"
+#define OOB_CPU_LIST	"/sys/module/xenomai/parameters/supported_cpus"
+
+static cpu_set_t isolated_cpus;
+
+#define OOB_GPIO_LAT    1
+#define INBAND_GPIO_LAT 2
+
+#define LATMON_TIMEOUT_SECS  5
+
+static int test_irqlat, test_klat,
+	test_ulat, test_sirqlat,
+	test_gpiolat;
+
+static bool reset, background,
+	abort_on_switch = true;
+
+static int verbosity = 1,
+	abort_threshold;
+
+static bool tuning;
+
+static time_t timeout;
+
+static time_t start_time;
+
+static unsigned int period_usecs = 1000; /* 1ms */
+
+static int responder_priority = 98;
+
+static int responder_cpu = -1;
+
+static int responder_cpu_state;
+
+static struct in_addr gpio_monitor_ip;
+
+static sigset_t sigmask;
+
+static int latmus_fd = -1;
+
+static int gpio_infd = -1, gpio_outfd = -1;
+
+static int gpio_inpin, gpio_outpin;
+
+static int gpio_hdinflags = GPIOHANDLE_REQUEST_INPUT,
+	gpio_hdoutflags = GPIOHANDLE_REQUEST_OUTPUT;
+
+static int gpio_evinflags;
+
+static pthread_t responder, logger;
+
+static sem_t logger_done;
+
+static bool c_state_restricted;
+
+static bool force_cpu;
+
+#define short_optlist "ikusrqbKmtp:A:T:v::l:g::H:P:c:Z:z:I:O:C:"
+
+static const struct option options[] = {
+	{
+		.name = "irq",
+		.has_arg = no_argument,
+		.val = 'i'
+	},
+	{
+		.name = "kernel",
+		.has_arg = no_argument,
+		.val = 'k'
+	},
+	{
+		.name = "user",
+		.has_arg = no_argument,
+		.val = 'u'
+	},
+	{
+		.name = "sirq",
+		.has_arg = no_argument,
+		.val = 's'
+	},
+	{
+		.name = "reset",
+		.has_arg = no_argument,
+		.val = 'r'
+	},
+	{
+		.name = "quiet",
+		.has_arg = no_argument,
+		.val = 'q'
+	},
+	{
+		.name = "background",
+		.has_arg = no_argument,
+		.val = 'b'
+	},
+	{
+		.name = "keep-going",
+		.has_arg = no_argument,
+		.val = 'K'
+	},
+	{
+		.name = "measure",
+		.has_arg = no_argument,
+		.val = 'm',
+	},
+	{
+		.name = "tune",
+		.has_arg = no_argument,
+		.val = 't',
+	},
+	{
+		.name = "period",
+		.has_arg = required_argument,
+		.val = 'p',
+	},
+	{
+		.name = "timeout",
+		.has_arg = required_argument,
+		.val = 'T',
+	},
+	{
+		.name = "maxlat-abort",
+		.has_arg = required_argument,
+		.val = 'A',
+	},
+	{
+		.name = "verbose",
+		.has_arg = optional_argument,
+		.val = 'v',
+	},
+	{
+		.name = "lines",
+		.has_arg = required_argument,
+		.val = 'l',
+	},
+	{
+		.name = "plot",
+		.has_arg = optional_argument,
+		.val = 'g',
+	},
+	{
+		.name = "histogram",
+		.has_arg = required_argument,
+		.val = 'H',
+	},
+	{
+		.name = "priority",
+		.has_arg = required_argument,
+		.val = 'P',
+	},
+	{
+		.name = "cpu",
+		.has_arg = required_argument,
+		.val = 'c',
+	},
+	{
+		.name = "force-cpu",
+		.has_arg = required_argument,
+		.val = 'C',
+	},
+	{
+		.name = "oob-gpio",
+		.has_arg = required_argument,
+		.val = 'Z',
+	},
+	{
+		.name = "inband-gpio",
+		.has_arg = required_argument,
+		.val = 'z',
+	},
+	{
+		.name = "gpio-in",
+		.has_arg = required_argument,
+		.val = 'I',
+	},
+	{
+		.name = "gpio-out",
+		.has_arg = required_argument,
+		.val = 'O',
+	},
+	{ /* Sentinel */ }
+};
+
+static inline unsigned int stack_size(unsigned int size)
+{
+	return size > PTHREAD_STACK_MIN ? size : PTHREAD_STACK_MIN;
+}
+
+static void create_responder(pthread_t *tid, void *(*responder)(void *))
+{
+	struct sched_param param;
+	pthread_attr_t attr;
+	int ret;
+
+	pthread_attr_init(&attr);
+	pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+	pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED);
+	pthread_attr_setschedpolicy(&attr, SCHED_FIFO);
+	param.sched_priority = responder_priority;
+	pthread_attr_setschedparam(&attr, &param);
+	pthread_attr_setstacksize(&attr,  stack_size(65536));
+	ret = pthread_create(tid, &attr, responder, NULL);
+	pthread_attr_destroy(&attr);
+	if (ret)
+		error(1, ret, "sampling thread");
+}
+
+#define ONE_BILLION	1000000000
+#define TEN_MILLIONS	10000000
+
+static int lat_xfd = -1;
+
+static int lat_sock = -1;
+
+static int data_lines = 21;
+
+static int32_t *histogram;
+
+static unsigned int histogram_cells = 200;
+
+static struct latmus_measurement last_bulk;
+
+static unsigned int all_overruns;
+
+static unsigned int spurious_inband_switches;
+
+static int32_t all_minlat = TEN_MILLIONS, all_maxlat = -TEN_MILLIONS;
+
+static int64_t all_sum;
+
+static int64_t all_samples;
+
+static time_t peak_time;
+
+static FILE *plot_fp;
+
+#define COBALT_LAT_OOB_GPIO      (COBALT_LAT_LAST + 1)
+#define COBALT_LAT_INBAND_GPIO   (COBALT_LAT_OOB_GPIO + 1)
+
+static int context_type = COBALT_LAT_USER;
+
+const char *context_labels[] = {
+	[COBALT_LAT_IRQ] = "irq",
+	[COBALT_LAT_SIRQ] = "sirq",
+	[COBALT_LAT_KERN] = "kernel",
+	[COBALT_LAT_USER] = "user",
+	[COBALT_LAT_OOB_GPIO] = "oob-gpio",
+	[COBALT_LAT_INBAND_GPIO] = "inband-gpio",
+};
+
+static void __log_results(struct latmus_measurement *meas)
+{
+	if (meas->min_lat < all_minlat)
+		all_minlat = meas->min_lat;
+	if (meas->max_lat > all_maxlat) {
+		peak_time = time(NULL) - start_time - 1;
+		all_maxlat = meas->max_lat;
+		if (abort_threshold && all_maxlat > abort_threshold) {
+			fprintf(stderr, "latency threshold is exceeded"
+				" (%d >= %.3f), aborting.\n",
+				abort_threshold,
+				(double)all_maxlat / 1000.0);
+			exit(102);
+		}
+	}
+
+	all_sum += meas->sum_lat;
+	all_samples += meas->samples;
+	all_overruns += meas->overruns;
+}
+
+static void log_results(struct latmus_measurement *meas,
+			unsigned int round)
+{
+	double min, avg, max, best, worst;
+	bool oops = false;
+	time_t now, dt;
+
+	if (verbosity > 0 && data_lines && (round % data_lines) == 0) {
+		time(&now);
+		dt = now - start_time - 1; /* -1s warm-up time */
+		printf("RTT|  %.2ld:%.2ld:%.2ld  (%s, %u us period,",
+			dt / 3600, (dt / 60) % 60, dt % 60,
+			context_labels[context_type], period_usecs);
+		if (context_type != COBALT_LAT_IRQ && context_type != COBALT_LAT_SIRQ)
+			printf(" priority %d,", responder_priority);
+		printf(" CPU%d%s)\n",
+			responder_cpu,
+			responder_cpu_state & COBALT_CPU_ISOL ? "" : "-noisol");
+		printf("RTH|%11s|%11s|%11s|%8s|%6s|%11s|%11s\n",
+		       "----lat min", "----lat avg",
+		       "----lat max", "-overrun", "---msw",
+		       "---lat best", "--lat worst");
+	}
+
+	__log_results(meas);
+	min = (double)meas->min_lat / 1000.0;
+	avg = (double)(meas->sum_lat / (int)meas->samples) / 1000.0;
+	max = (double)meas->max_lat / 1000.0;
+	best = (double)all_minlat / 1000.0;
+	worst = (double)all_maxlat / 1000.0;
+
+	/*
+	 * A trivial check on the reported values, so that we detect
+	 * and stop on obviously inconsistent results.
+	 */
+	if (min > max || min > avg || avg > max ||
+		min > worst || max > worst || avg > worst ||
+		best > worst || worst < best) {
+		oops = true;
+		verbosity = 1;
+	}
+
+	if (verbosity > 0)
+		printf("RTD|%11.3f|%11.3f|%11.3f|%8d|%6u|%11.3f|%11.3f\n",
+			min, avg, max,
+			all_overruns, spurious_inband_switches,
+			best, worst);
+
+	if (max > 1000)
+		exit(103);
+	if (oops) {
+		fprintf(stderr, "results look weird, aborting.\n");
+		exit(103);
+	}
+}
+
+static inline void notify_start(void)
+{
+	if (timeout)
+		alarm(timeout + 1); /* +1 warm-up time */
+}
+
+static void create_logger(pthread_t *tid, void *(*logger)(void *), void *arg)
+{
+	struct sched_param param;
+	pthread_attr_t attr;
+	int ret;
+
+	sem_init(&logger_done, 0, 0);
+
+	pthread_attr_init(&attr);
+	pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+	pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED);
+	pthread_attr_setschedpolicy(&attr, SCHED_OTHER);
+	param.sched_priority = 0;
+	pthread_attr_setschedparam(&attr, &param);
+	pthread_attr_setstacksize(&attr, stack_size(65536));
+	ret = pthread_create(tid, &attr, logger, arg);
+	pthread_attr_destroy(&attr);
+	if (ret)
+		error(1, ret, "logger thread");
+}
+
+static void *xbuf_logger_thread(void *arg)
+{
+	struct latmus_measurement meas;
+	ssize_t ret, round = 0;
+
+	for (;;) {
+		ret = read(lat_xfd, &meas, sizeof(meas));
+		if (ret != sizeof(meas))
+			break;
+		log_results(&meas, round++);
+	}
+
+	/* Nobody waits for logger_done in timer mode. */
+
+	return NULL;
+}
+
+static void *timer_responder(void *arg)
+{
+	__u64 timestamp = 0;
+	struct timespec now;
+	int ret;
+
+	for (;;) {
+		ret = ioctl(latmus_fd, RTTST_RTIOC_COBALT_LATIOC_PULSE,
+				&timestamp);
+		if (ret) {
+			if (errno != EPIPE)
+				error(1, errno, "pulse failed");
+			timestamp = 0; /* Next period. */
+		} else {
+			clock_gettime(CLOCK_MONOTONIC, &now);
+			timestamp = (__u64)now.tv_sec * 1000000000 + now.tv_nsec;
+		}
+	}
+
+	return NULL;
+}
+
+static void *timer_test_sitter(void *arg)
+{
+	struct latmus_measurement_result mr;
+	struct latmus_result result;
+	int ret;
+
+	mr.last_ptr = (__u64)(uintptr_t)&last_bulk;
+	mr.histogram_ptr = (__u64)(uintptr_t)histogram;
+	mr.len = histogram ? histogram_cells * sizeof(int32_t) : 0;
+
+	result.data_ptr = (__u64)(uintptr_t)&mr;
+	result.len = sizeof(mr);
+
+	notify_start();
+
+	/* Run test until signal. */
+	ret = ioctl(latmus_fd, RTTST_RTIOC_COBALT_LATIOC_RUN, &result);
+	if (ret)
+		error(1, errno, "measurement failed");
+
+	return NULL;
+}
+
+static void setup_measurement_on_timer(void)
+{
+	struct latmus_setup setup;
+	pthread_attr_t attr;
+	pthread_t sitter;
+	int ret, sig;
+	char *rtp;
+
+	memset(&setup, 0, sizeof(setup));
+	setup.type = context_type;
+	setup.period = period_usecs * 1000ULL; /* ns */
+	setup.priority = responder_priority;
+	setup.cpu = responder_cpu;
+	setup.u.measure.hcells = histogram ? histogram_cells : 0;
+	ret = ioctl(latmus_fd, RTTST_RTIOC_COBALT_LATIOC_MEASURE, &setup);
+	if (ret < 0)
+		error(1, errno, "measurement setup failed");
+
+	/*open xnpipe to exchange message*/
+	if (asprintf(&rtp, "/dev/rtp%d", ret) < 0)
+		error(1, ENOMEM, "resolve rtp name");
+	lat_xfd = open(rtp, O_RDWR);
+	if (lat_xfd < 0)
+		error(1, -lat_xfd, "cannot create rtp");
+	free(rtp);
+	create_logger(&logger, xbuf_logger_thread, NULL);
+
+	if (context_type == COBALT_LAT_USER)
+		create_responder(&responder, timer_responder);
+
+	pthread_attr_init(&attr);
+	pthread_attr_setstacksize(&attr, stack_size(65536));
+	ret = pthread_create(&sitter, &attr, timer_test_sitter, NULL);
+	pthread_attr_destroy(&attr);
+	if (ret)
+		error(1, ret, "timer_test_sitter");
+
+	sigwait(&sigmask, &sig);
+	pthread_cancel(sitter);
+	pthread_join(sitter, NULL);
+
+	/*
+	 * Add results from the last incomplete bulk once the sitter
+	 * has returned to user-space from oob_ioctl(COBALT_LATIOC_RUN)
+	 * then exited, at which point such bulk contains meaningful
+	 * data.
+	 */
+	if (last_bulk.samples > 0)
+		__log_results(&last_bulk);
+}
+
+static void setup_gpio_pins(int *fds)
+{
+	int value;
+	int ret;
+
+	ret = ioctl(gpio_infd, GPIO_RTIOC_IRQEN, &gpio_evinflags);
+	if (ret)
+		error(1, errno, "ioctl(GPIO_RTIOC_IRQEN)");
+
+	value = 1;
+	ret = ioctl(gpio_infd, GPIO_RTIOC_TS, &value);
+	if (ret)
+		error(1, errno, "ioctl(GPIO_RTIOC_TS)");
+
+	value = 1;
+	ret = ioctl(gpio_outfd, GPIO_RTIOC_DIR_OUT, &value);
+	if (ret)
+		error(1, errno, "ioctl(GPIO_RTIOC_DIR_OUT)");
+
+	fds[0] = gpio_infd;
+	fds[1] = gpio_outfd;
+}
+
+static void *gpio_responder_thread(void *arg)
+{
+	int value;
+	struct rtdm_gpio_readout rdo;
+	const int ackval = 0;	/* Remote observes falling edges. */
+	int fds[2], ret;
+
+	setup_gpio_pins(fds);
+
+	for (;;) {
+		value = !ackval;
+		ret = write(fds[1], &value, sizeof(value));
+		if (ret < 0)
+			error(1, errno, "write failed");
+
+		ret = read(fds[0], &rdo,
+				sizeof(struct rtdm_gpio_readout));
+		if (ret != sizeof(struct rtdm_gpio_readout))
+			break;
+
+		value = ackval;
+		ret = write(fds[1], &value, sizeof(value));
+		if (ret < 0)
+			error(1, errno, "write failed");
+	}
+
+	return NULL;
+}
+
+static ssize_t read_net_data(void *buf, size_t len)
+{
+	ssize_t count = 0, ret;
+	struct pollfd pollfd;
+
+	pollfd.fd = lat_sock;
+	pollfd.events = POLLIN;
+	pollfd.revents = 0;
+
+	do {
+		/* Make sure to detect latmon unresponsivess. */
+		ret = poll(&pollfd, 1, LATMON_TIMEOUT_SECS * 1000);
+		if (ret <= 0)
+			return -ETIMEDOUT;
+		ret = recv(lat_sock, buf + count, len - count, 0);
+		if (ret <= 0)
+			return ret;
+		count += ret;
+	} while (count < len);
+
+	return count;
+}
+
+static void *sock_logger_thread(void *arg)
+{
+	struct latmus_measurement meas;
+	struct latmon_net_data ndata;
+	bool *no_response = arg;
+	ssize_t ret, round = 0;
+	int cell;
+
+	for (;;) {
+		ret = read_net_data(&ndata, sizeof(ndata));
+		if (ret <= 0)
+			goto unresponsive;
+
+		/*
+		 * Receiving an empty data record means that we got
+		 * the trailing data in the previous round, so
+		 * we are done with sample bulks now.
+		 */
+		if (ndata.samples == 0)
+			break;
+
+		/* This is valid sample data, log it. */
+		meas.sum_lat = ((__s64)ntohl(ndata.sum_lat_hi)) << 32 |
+			ntohl(ndata.sum_lat_lo);
+		meas.min_lat = ntohl(ndata.min_lat);
+		meas.max_lat = ntohl(ndata.max_lat);
+		meas.overruns = ntohl(ndata.overruns);
+		meas.samples = ntohl(ndata.samples);
+		log_results(&meas, round++);
+	}
+
+	if (histogram == NULL)
+		goto out;
+
+	ret = read_net_data(histogram, histogram_cells * sizeof(int32_t));
+	if (ret <= 0) {
+unresponsive:
+		*no_response = true;
+		kill(getpid(), SIGHUP);
+	} else {
+		for (cell = 0; cell < histogram_cells; cell++)
+			histogram[cell] = ntohl(histogram[cell]);
+	}
+out:
+	sem_post(&logger_done);
+
+	return NULL;
+}
+
+static void setup_measurement_on_gpio(void)
+{
+	struct latmon_net_request req;
+	struct sockaddr_in in_addr;
+	bool latmon_hung = false;
+	struct timespec timeout;
+	int ret, sig;
+
+	lat_sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+	if (lat_sock < 0)
+		error(1, errno, "socket()");
+
+	if (verbosity)
+		printf("connecting to latmon at %s:%d...\n",
+			inet_ntoa(gpio_monitor_ip), LATMON_NET_PORT);
+
+	memset(&in_addr, 0, sizeof(in_addr));
+	in_addr.sin_family = AF_INET;
+	in_addr.sin_addr = gpio_monitor_ip;
+	in_addr.sin_port = htons(LATMON_NET_PORT);
+	ret = connect(lat_sock, (struct sockaddr *)&in_addr,
+		sizeof(in_addr));
+	if (ret)
+		error(1, errno, "connect()");
+
+	if (verbosity && context_type == COBALT_LAT_INBAND_GPIO)
+		printf("CAUTION: measuring in-band response time (no COBALT there)\n");
+
+	create_responder(&responder, gpio_responder_thread);
+	create_logger(&logger, sock_logger_thread, &latmon_hung);
+
+	notify_start();
+	req.period_usecs = htonl(period_usecs); /* Non-zero, means start. */
+	req.histogram_cells = histogram ? htonl(histogram_cells) : 0;
+	ret = send(lat_sock, &req, sizeof(req), 0);
+	if (ret != sizeof(req))
+		error(1, errno, "send() start");
+
+	sigwait(&sigmask, &sig);
+
+	/*
+	 * From now on, we may wait up to LATMON_TIMEOUT_SECS
+	 * max. between messages from the remote latency monitor
+	 * before declaring it unresponsive.
+	 */
+	if (!latmon_hung) {
+		req.period_usecs = 0; /* Zero means stop. */
+		req.histogram_cells = 0;
+		ret = send(lat_sock, &req, sizeof(req), 0);
+		if (ret != sizeof(req)) {
+			error(1, errno, "send() stop");
+			latmon_hung = true;
+		} else {
+			clock_gettime(CLOCK_REALTIME, &timeout);
+			timeout.tv_sec += LATMON_TIMEOUT_SECS;
+			if (sem_timedwait(&logger_done, &timeout))
+				latmon_hung = true;
+		}
+	}
+
+	if (latmon_hung)
+		error(1, ETIMEDOUT, "latmon at %s is unresponsive",
+			inet_ntoa(gpio_monitor_ip));
+
+	close(lat_sock);
+}
+
+static void paste_file_in(const char *path, const char *header)
+{
+	char buf[BUFSIZ];
+	FILE *fp;
+
+	fp = fopen(path, "r");
+	if (fp == NULL)
+		return;
+
+	fprintf(plot_fp, "# %s", header ?: "");
+
+	while (fgets(buf, sizeof(buf), fp))
+		fputs(buf, plot_fp);
+
+	fclose(fp);
+}
+
+static void dump_gnuplot(time_t duration)
+{
+	int first, last, n;
+
+	if (all_samples == 0)
+		return;
+
+	fprintf(plot_fp, "# test started on: %s", ctime(&start_time));
+	paste_file_in("/proc/version", NULL);
+	paste_file_in("/proc/cmdline", NULL);
+	//fprintf(plot_fp, "# libevl version: %s\n", evl_get_version().version_string);
+	fprintf(plot_fp, "# sampling period: %u microseconds\n", period_usecs);
+	paste_file_in("/sys/devices/virtual/clock/monotonic/gravity",
+		"clock gravity: ");
+	paste_file_in("/sys/devices/system/clocksource/clocksource0/current_clocksource",
+		"clocksource: ");
+	paste_file_in("/sys/devices/system/clocksource/clocksource0/vdso_clocksource",
+		"vDSO access: ");
+	fprintf(plot_fp, "# context: %s\n", context_labels[context_type]);
+	if (!(test_irqlat || test_sirqlat)) {
+		fprintf(plot_fp, "# thread priority: %d\n", responder_priority);
+		fprintf(plot_fp, "# thread affinity: CPU%d%s\n",
+			responder_cpu,
+			responder_cpu_state & COBALT_CPU_ISOL ? "" : "-noisol");
+	}
+	if (c_state_restricted)
+		fprintf(plot_fp, "# C-state restricted\n");
+	fprintf(plot_fp, "# duration (hhmmss): %.2ld:%.2ld:%.2ld\n",
+		duration / 3600, (duration / 60) % 60, duration % 60);
+	fprintf(plot_fp, "# peak (hhmmss): %.2ld:%.2ld:%.2ld\n",
+		peak_time / 3600, (peak_time / 60) % 60, peak_time % 60);
+	if (all_overruns > 0)
+		fprintf(plot_fp, "# OVERRUNS: %u\n", all_overruns);
+	if (spurious_inband_switches > 0)
+		fprintf(plot_fp, "# IN-BAND SWITCHES: %u\n", spurious_inband_switches);
+	fprintf(plot_fp, "# min latency: %.3f\n",
+		(double)all_minlat / 1000.0);
+	fprintf(plot_fp, "# avg latency: %.3f\n",
+		(double)(all_sum / all_samples) / 1000.0);
+	fprintf(plot_fp, "# max latency: %.3f\n",
+		(double)all_maxlat / 1000.0);
+	fprintf(plot_fp, "# sample count: %lld\n",
+		(long long)all_samples);
+
+	for (n = 0; n < histogram_cells && histogram[n] == 0; n++)
+		;
+	first = n;
+
+	for (n = histogram_cells - 1; n >= 0 && histogram[n] == 0; n--)
+		;
+	last = n;
+
+	for (n = first; n < last; n++)
+		fprintf(plot_fp, "%d %d\n", n, histogram[n]);
+
+	/*
+	 * If we have outliers, display a '+' sign after the last cell
+	 * index.
+	 */
+	fprintf(plot_fp, "%d%s %d\n", last,
+		all_maxlat / 1000 >= histogram_cells ? "+" : "",
+		histogram[last]);
+}
+
+static void do_measurement(int type)
+{
+	const char *cpu_s = "";
+	time_t duration;
+
+	context_type = type;
+
+	if (plot_fp) {
+		histogram = malloc(histogram_cells * sizeof(int32_t));
+		if (histogram == NULL)
+			error(1, ENOMEM, "cannot get memory");
+	}
+
+	if (!(responder_cpu_state & COBALT_CPU_ISOL))
+		cpu_s = " (not isolated)";
+
+	if (verbosity > 0)
+		fprintf(stderr, "warming up on CPU%d%s...\n", responder_cpu, cpu_s);
+	else
+		fprintf(stderr, "running quietly for %ld seconds on CPU%d%s\n",
+			timeout, responder_cpu, cpu_s);
+
+	switch (type) {
+	case COBALT_LAT_OOB_GPIO:
+	case COBALT_LAT_INBAND_GPIO:
+		setup_measurement_on_gpio();
+		break;
+	default:
+		setup_measurement_on_timer();
+	}
+
+	duration = time(NULL) - start_time - 1; /* -1s warm-up time */
+	if (plot_fp) {
+		dump_gnuplot(duration);
+		if (plot_fp != stdout)
+			fclose(plot_fp);
+		free(histogram);
+	}
+
+	if (!timeout)
+		timeout = duration;
+
+	if (all_samples > 0)
+		printf("---|-----------|-----------|-----------|--------"
+			"|------|-------------------------\n"
+			"RTS|%11.3f|%11.3f|%11.3f|%8d|%6u|    "
+			"%.2ld:%.2ld:%.2ld/%.2ld:%.2ld:%.2ld\n",
+			(double)all_minlat / 1000.0,
+			(double)(all_sum / all_samples) / 1000.0,
+			(double)all_maxlat / 1000.0,
+			all_overruns, spurious_inband_switches,
+			duration / 3600, (duration / 60) % 60,
+			duration % 60, duration / 3600,
+			(timeout / 60) % 60, timeout % 60);
+
+	if (spurious_inband_switches > 0) {
+		if (all_samples > 0)
+			fputc('\n', stderr);
+		fprintf(stderr, "*** WARNING: unexpected switches to in-band mode detected,\n"
+		       "             latency figures displayed are NOT reliable.\n"
+		       "             Please submit a bug report upstream.\n");
+		if (abort_on_switch) {
+			abort_on_switch = false;
+			fprintf(stderr, "*** OOPS: aborting upon spurious switch to in-band mode.\n");
+		}
+	}
+
+	if (responder)
+		pthread_cancel(responder);
+
+	if (logger)
+		pthread_cancel(logger);
+}
+
+static void do_tuning(int type)
+{
+	struct latmus_result result;
+	struct latmus_setup setup;
+	pthread_t responder;
+	__s32 gravity;
+	int ret;
+
+	if (verbosity) {
+		printf("%s gravity...", context_labels[type]);
+		fflush(stdout);
+	}
+
+	memset(&setup, 0, sizeof(setup));
+	setup.type = type;
+	setup.period = period_usecs * 1000ULL; /* ns */
+	setup.priority = responder_priority;
+	setup.cpu = responder_cpu;
+	setup.u.tune.verbosity = verbosity;
+	ret = ioctl(latmus_fd, RTTST_RTIOC_COBALT_LATIOC_TUNE, &setup);
+	if (ret)
+		error(1, errno, "tuning setup failed (%s)", context_labels[type]);
+
+	if (type == COBALT_LAT_USER)
+		create_responder(&responder, timer_responder);
+
+	pthread_sigmask(SIG_UNBLOCK, &sigmask, NULL);
+
+	notify_start();
+
+	result.data_ptr = (__u64)(uintptr_t)&gravity;
+	result.len = sizeof(gravity);
+	ret = ioctl(latmus_fd, RTTST_RTIOC_COBALT_LATIOC_RUN, &result);
+	if (ret)
+		error(1, errno, "measurement failed");
+
+	if (type == COBALT_LAT_USER)
+		pthread_cancel(responder);
+
+	if (verbosity)
+		printf("%u ns\n", gravity);
+}
+
+#ifdef CONFIG_XENO_COBALT
+
+#include <cobalt/uapi/syscall.h>
+
+static void sigdebug_handler(int sig, siginfo_t *si, void *context)
+{
+	unsigned int reason = sigdebug_reason(si);
+
+	if (reason > SIGDEBUG_WATCHDOG)
+		reason = SIGDEBUG_UNDEFINED;
+
+	switch (reason) {
+	case SIGDEBUG_UNDEFINED:
+	case SIGDEBUG_NOMLOCK:
+	case SIGDEBUG_WATCHDOG:
+		exit(99);
+	}
+
+	spurious_inband_switches++;
+	if (abort_on_switch)
+		kill(getpid(), SIGHUP);
+}
+#endif /* CONFIG_XENO_COBALT */
+
+static void set_cpu_affinity(void)
+{
+	cpu_set_t cpu_set;
+	int ret;
+
+	CPU_ZERO(&cpu_set);
+	CPU_SET(responder_cpu, &cpu_set);
+	ret = sched_setaffinity(0, sizeof(cpu_set), &cpu_set);
+	if (ret)
+		error(1, errno, "cannot set affinity to CPU%d",
+		      responder_cpu);
+}
+
+static void restrict_c_state(void)
+{
+	__s32 val = 0;
+	int fd;
+
+	fd = open("/dev/cpu_dma_latency", O_WRONLY);
+	if (fd < 0)
+		return;
+
+	if (write(fd, &val, sizeof(val) == sizeof(val)))
+		c_state_restricted = true;
+}
+
+static void parse_host_spec(const char *host, struct in_addr *in_addr)
+{
+	struct addrinfo hints, *res;
+	int ret;
+
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = AF_INET;
+	hints.ai_socktype = SOCK_STREAM;
+	hints.ai_flags = AI_ADDRCONFIG;
+	ret = getaddrinfo(host, NULL, &hints, &res);
+	if (ret)
+		error(1, ret == EAI_SYSTEM ? errno : ESRCH,
+			"getaddrinfo(%s)", host);
+
+	*in_addr = ((struct sockaddr_in *)res->ai_addr)->sin_addr;
+}
+
+static int parse_gpio_spec(const char *spec, int *pin,
+			int *hdflags, int *evflags)
+{
+	char *s, *dev, *p, *endptr, *devname;
+	int fd, ret;
+
+	s = strdup(spec);
+	dev = strtok(s, ",");
+	if (dev == NULL)
+		error(1, EINVAL, "no GPIO device in spec: %s", spec);
+
+	p = strtok(NULL, ",");
+	if (p == NULL)
+		error(1, EINVAL, "no GPIO pin in spec: %s", spec);
+
+	*pin = (int)strtol(p, &endptr, 10);
+	if (*pin < 0 || endptr == p)
+		error(1, EINVAL, "invalid GPIO pin number in spec: %s",
+			spec);
+
+	ret = asprintf(&devname, "/dev/rtdm/%s/gpio%d", dev, *pin);
+	if (ret < 0)
+		error(1, ENOMEM, "asprintf()");
+
+	p = strtok(NULL, ",");
+	if (evflags) {
+		if (p) {
+			if (!strcmp(p, "rising-edge"))
+				*evflags = GPIO_TRIGGER_EDGE_FALLING;
+			else if  (!strcmp(p, "falling-edge"))
+				*evflags = GPIO_TRIGGER_EDGE_RISING;
+			else
+				error(1, EINVAL, "invalid edge type in spec: %s",
+					spec);
+		} else	/* Default is rising edge. */
+			*evflags = GPIO_TRIGGER_EDGE_RISING;
+	} else if (p)
+		error(1, EINVAL, "trailing garbage in spec: %s",
+			spec);
+
+	fd = open(devname, O_RDONLY);
+	if (fd < 0)
+		error(1, errno, "open(%s)", devname);
+
+	free(devname);
+	free(s);
+
+	return fd;
+}
+
+static int get_realtime_cpu_set(cpu_set_t *cpuset)
+{
+	unsigned long long cpumask;
+	char buf[BUFSIZ], *p;
+	FILE *fp;
+	int cpu;
+
+	fp = fopen("/sys/module/xenomai/parameters/supported_cpus", "r");
+	if (fp == NULL)
+		return -ENOENT;
+
+	p = fgets(buf, sizeof(buf), fp);
+	fclose(fp);
+	if (p == NULL)
+		return -EBADF;
+
+	errno = 0;
+	cpumask = strtoll(p, NULL, 10);
+	if (cpumask == LLONG_MAX && errno == ERANGE)
+		cpumask = ULLONG_MAX;
+	for (cpu = 0; cpumask != 0; cpu++, cpumask >>= 1) {
+		if (cpumask & 1ULL)
+			CPU_SET(cpu, cpuset);
+	}
+
+	return 0;
+}
+
+static void parse_cpu_list(const char *path, cpu_set_t *cpuset)
+{
+	char *p, *range, *range_p = NULL, *id, *id_r;
+	int start, end, cpu;
+	char buf[BUFSIZ];
+	FILE *fp;
+
+	CPU_ZERO(cpuset);
+
+	fp = fopen(path, "r");
+	if (fp == NULL)
+		return;
+
+	if (!fgets(buf, sizeof(buf), fp))
+		goto out;
+
+	p = buf;
+	while ((range = strtok_r(p, ",", &range_p)) != NULL) {
+		if (*range == '\0' || *range == '\n')
+			goto next;
+		end = -1;
+		id = strtok_r(range, "-", &id_r);
+		if (id) {
+			start = atoi(id);
+			id = strtok_r(NULL, "-", &id_r);
+			if (id)
+				end = atoi(id);
+			else if (end < 0)
+				end = start;
+			for (cpu = start; cpu <= end; cpu++)
+				CPU_SET(cpu, cpuset);
+		}
+next:
+		p = NULL;
+	}
+out:
+	fclose(fp);
+}
+
+static void determine_responder_cpu(bool inband_test)
+{
+	cpu_set_t oob_cpus, best_cpus;
+	int cpu;
+
+	parse_cpu_list(ISOLATED_CPU_LIST, &isolated_cpus);
+	get_realtime_cpu_set(&oob_cpus);
+	if (responder_cpu >= 0) {
+		if (!inband_test && !CPU_ISSET(responder_cpu, &oob_cpus)) {
+			if (verbosity)
+				printf("CPU%d is not OOB-capable, "
+					"picking a better one\n",
+					responder_cpu);
+			goto pick_oob;
+		}
+		goto finish;
+	}
+
+	if (force_cpu)
+		goto finish;
+
+	if (inband_test)
+		goto pick_isolated;
+
+	/*
+	 * Pick a default CPU among the ones which are both
+	 * OOB-capable and isolated. If COBALT is not enabled, oob_cpus
+	 * is empty so there is no best choice.
+	 */
+	CPU_AND(&best_cpus, &isolated_cpus, &oob_cpus);
+	for (cpu = 0; cpu < CPU_SETSIZE; cpu++) {
+		if (CPU_ISSET(cpu, &best_cpus)) {
+			responder_cpu = cpu;
+			goto finish;
+		}
+	}
+
+	/*
+	 * If no best choice, pick the first OOB-capable CPU we can
+	 * find (if any).
+	 */
+pick_oob:
+	for (cpu = 0; cpu < CPU_SETSIZE; cpu++) {
+		if (CPU_ISSET(cpu, &oob_cpus)) {
+			responder_cpu = cpu;
+			goto finish;
+		}
+	}
+
+pick_isolated:
+	/*
+	 * This must be a kernel with no COBALT support or we
+	 * specifically need an isolated CPU.
+	 */
+	for (cpu = 0; cpu < CPU_SETSIZE; cpu++) {
+		if (CPU_ISSET(cpu, &isolated_cpus)) {
+			responder_cpu = cpu;
+			goto finish;
+		}
+	}
+
+	/* Out of luck, run on the current CPU. */
+	if (responder_cpu < 0)
+		responder_cpu = sched_getcpu();
+finish:
+	if (CPU_ISSET(responder_cpu, &isolated_cpus))
+		responder_cpu_state = COBALT_CPU_ISOL;
+}
+
+static void usage(void)
+{
+	fprintf(stderr, "usage: latmus [options]:\n");
+	fprintf(stderr, "-m --measure            measure latency on timer event [default]\n");
+	fprintf(stderr, "-t --tune               tune the COBALT core timer\n");
+	fprintf(stderr, "-i --irq                measure/tune interrupt latency\n");
+	fprintf(stderr, "-k --kernel             measure/tune kernel scheduling latency\n");
+	fprintf(stderr, "-u --user               measure/tune user scheduling latency\n");
+	fprintf(stderr, "    [ if none of --irq, --kernel or --user is given,\n"
+			"      tune for all contexts ]\n");
+	fprintf(stderr, "-s --sirq               measure in-band response time to synthetic irq\n");
+	fprintf(stderr, "-p --period=<us>        sampling period\n");
+	fprintf(stderr, "-P --priority=<prio>    responder thread priority [=90]\n");
+	fprintf(stderr, "-c --cpu=<n>            pin responder thread to CPU [=current]\n");
+	fprintf(stderr, "-C --force-cpu=<n>      similar to -c, accept non-isolated CPU\n");
+	fprintf(stderr, "-r --reset              reset core timer gravity to factory default\n");
+	fprintf(stderr, "-b --background         run in the background (daemon mode)\n");
+	fprintf(stderr, "-K --keep-going         keep going on unexpected switch to in-band mode\n");
+	fprintf(stderr, "-A --max-abort=<us>     abort if maximum latency exceeds threshold\n");
+	fprintf(stderr, "-T --timeout=<t>[dhms]  stop measurement after <t> [d(ays)|h(ours)|m(inutes)|s(econds)]\n");
+	fprintf(stderr, "-v --verbose[=level]    set verbosity level [=1]\n");
+	fprintf(stderr, "-q --quiet              quiet mode (i.e. --verbose=0)\n");
+	fprintf(stderr, "-l --lines=<num>        result lines per page, 0 = no pagination [=21]\n");
+	fprintf(stderr, "-H --histogram[=<nr>]   set histogram size to <nr> cells [=200]\n");
+	fprintf(stderr, "-g --plot=<filename>    dump histogram data to file (gnuplot format)\n");
+	fprintf(stderr, "-Z --oob-gpio=<host>    measure COBALT response time to GPIO event via <host>\n");
+	fprintf(stderr, "-z --inband-gpio=<host> measure in-band response time to GPIO event via <host>\n");
+	fprintf(stderr, "-I --gpio-in=<spec>     input GPIO line configuration\n");
+	fprintf(stderr, "   with <spec> = gpiochip-devname,pin-number[,rising-edge|falling-edge]\n");
+	fprintf(stderr, "-O --gpio-out=<spec>    output GPIO line configuration\n");
+	fprintf(stderr, "   with <spec> = gpiochip-devname,pin-number\n");
+}
+
+static void bad_usage(int argc, char *const argv[])
+{
+	int last = optind < argc ? optind : argc - 1;
+
+	printf("** Uh, you lost me somewhere near '%s' (arg #%d)\n", argv[last], last);
+	usage();
+}
+
+int main(int argc, char *const argv[])
+{
+	int ret, c, spec, type, max_prio, lindex;
+	const char *plot_filename = NULL;
+	struct sigaction sa;
+	char *endptr;
+
+	opterr = 0;
+
+	for (;;) {
+		c = getopt_long(argc, argv, short_optlist, options, &lindex);
+		if (c == EOF)
+			break;
+
+		switch (c) {
+		case 0:
+			break;
+		case 'i':
+			test_irqlat = 1;
+			break;
+		case 'k':
+			test_klat = 1;
+			break;
+		case 'u':
+			test_ulat = 1;
+			break;
+		case 's':
+			test_sirqlat = 1;
+			break;
+		case 'r':
+			reset = true;
+			break;
+		case 'q':
+			verbosity = 0;
+			break;
+		case 'b':
+			background = true;
+			break;
+		case 'K':
+			abort_on_switch = false;
+			break;
+		case 'm':
+			tuning = false;
+			break;
+		case 't':
+			tuning = true;
+			break;
+		case 'p':
+			period_usecs = atoi(optarg);
+			if (period_usecs <= 0 || period_usecs > 1000000)
+				error(1, EINVAL, "invalid sampling period "
+				      "(0 < period < 1000000)");
+			break;
+		case 'A':
+			abort_threshold = atoi(optarg) * 1000; /* ns */
+			if (abort_threshold <= 0)
+				error(1, EINVAL, "invalid timeout");
+			break;
+		case 'T':
+			timeout = (int)strtol(optarg, &endptr, 10);
+			if (timeout < 0 || endptr == optarg)
+				error(1, EINVAL, "invalid timeout");
+			switch (*endptr) {
+			case 'd':
+				timeout *= 24;
+				/* Falldown wanted. */
+			case 'h':
+				timeout *= 60;
+				/* Falldown wanted. */
+			case 'm':
+				timeout *= 60;
+				break;
+			case 's':
+			case '\0':
+				break;
+			default:
+				error(1, EINVAL, "invalid time modifier: '%c'",
+					*endptr);
+			}
+			break;
+		case 'v':
+			verbosity = optarg ? atoi(optarg) : 1;
+			break;
+		case 'l':
+			data_lines = atoi(optarg);
+			break;
+		case 'g':
+			if (optarg && strcmp(optarg, "-"))
+				plot_filename = optarg;
+			else
+				plot_fp = stdout;
+			break;
+		case 'H':
+			histogram_cells = atoi(optarg);
+			if (histogram_cells < 1 || histogram_cells > 1000)
+				error(1, EINVAL, "invalid number of histogram cells "
+				      "(0 < cells <= 1000)");
+			break;
+		case 'P':
+			max_prio = sched_get_priority_max(SCHED_FIFO);
+			responder_priority = atoi(optarg);
+			if (responder_priority < 0 || responder_priority > max_prio)
+				error(1, EINVAL, "invalid thread priority "
+				      "(0 < priority < %d)", max_prio);
+			break;
+		case 'C':
+			force_cpu = true;
+			/* fallthrough */
+		case 'c':
+			responder_cpu = atoi(optarg);
+			if (responder_cpu < 0 || responder_cpu >= CPU_SETSIZE)
+				error(1, EINVAL, "invalid CPU number");
+			break;
+		case 'z':
+		case 'Z':
+			test_gpiolat = (c == 'z') + 1;
+			parse_host_spec(optarg, &gpio_monitor_ip);
+			break;
+		case 'I':
+			gpio_infd = parse_gpio_spec(optarg, &gpio_inpin,
+					&gpio_hdinflags, &gpio_evinflags);
+			break;
+		case 'O':
+			gpio_outfd = parse_gpio_spec(optarg, &gpio_outpin,
+					&gpio_hdoutflags, NULL);
+			break;
+		case '?':
+		default:
+			bad_usage(argc, argv);
+			return 1;
+		}
+	}
+
+	if (optind < argc) {
+		bad_usage(argc, argv);
+		return 1;
+	}
+
+	determine_responder_cpu(test_gpiolat == INBAND_GPIO_LAT);
+
+	setlinebuf(stdout);
+	setlinebuf(stderr);
+
+	if (!tuning && !timeout && !verbosity) {
+		fprintf(stderr, "--quiet requires --timeout, ignoring --quiet\n");
+		verbosity = 1;
+	}
+
+	if (background && verbosity) {
+		fprintf(stderr, "--background requires --quiet, taming verbosity down\n");
+		verbosity = 0;
+	}
+
+	if (tuning && (plot_filename || plot_fp)) {
+		fprintf(stderr, "--plot implies --measure, ignoring --plot\n");
+		plot_filename = NULL;
+		plot_fp = NULL;
+	}
+
+	if (background) {
+		signal(SIGHUP, SIG_IGN);
+		ret = daemon(0, 0);
+		if (ret)
+			error(1, errno, "cannot daemonize");
+	}
+
+	set_cpu_affinity();
+	restrict_c_state();
+
+	sigaddset(&sigmask, SIGINT);
+	sigaddset(&sigmask, SIGTERM);
+	sigaddset(&sigmask, SIGHUP);
+	sigaddset(&sigmask, SIGALRM);
+	pthread_sigmask(SIG_BLOCK, &sigmask, NULL);
+
+#ifdef CONFIG_XENO_COBALT
+	sigemptyset(&sa.sa_mask);
+	sa.sa_sigaction = sigdebug_handler;
+	sa.sa_flags = SA_SIGINFO | SA_RESTART;
+	sigaction(SIGDEBUG, &sa, NULL);
+#endif
+
+	spec = test_irqlat || test_klat || test_ulat || test_sirqlat || test_gpiolat;
+	if (!tuning) {
+		if (!spec)
+			test_ulat = 1;
+		else if (test_irqlat + test_klat + test_ulat + test_sirqlat +
+			(!!test_gpiolat) > 1)
+			error(1, EINVAL, "only one of -u, -k, -i, -s, -z or -Z "
+			      "in measurement mode");
+	} else {
+		/* Default to tune for all contexts. */
+		if (!spec)
+			test_irqlat = test_klat = test_ulat = 1;
+		else if (test_sirqlat || test_gpiolat)
+			error(1, EINVAL, "-s/-z and -t are mutually exclusive");
+	}
+
+	if (!test_gpiolat) {
+		latmus_fd = open("/dev/rtdm/latmus", O_RDWR);
+		if (latmus_fd < 0)
+			error(1, errno, "cannot open latmus device");
+
+		if (reset) {
+			ret = ioctl(latmus_fd, RTTST_RTIOC_COBALT_LATIOC_RESET);
+			if (ret)
+				error(1, errno, "reset failed");
+		}
+	} else {
+		if (gpio_infd < 0 || gpio_outfd < 0)
+			error(1, EINVAL, "-[zZ] require -I, -O for GPIO settings");
+		if (test_gpiolat == OOB_GPIO_LAT) {
+			//gpio_hdinflags |= GPIOHANDLE_REQUEST_OOB;
+			//gpio_hdoutflags |= GPIOHANDLE_REQUEST_OOB;
+		}
+	}
+
+	time(&start_time);
+
+	if (!tuning) {
+		if (plot_filename) {
+			if (!access(plot_filename, F_OK))
+				error(1, EINVAL, "declining to overwrite %s",
+				      plot_filename);
+			plot_fp = fopen(plot_filename, "w");
+			if (plot_fp == NULL)
+				error(1, errno, "cannot open %s for writing",
+				      plot_filename);
+		}
+		type = test_irqlat ? COBALT_LAT_IRQ : test_klat ?
+			COBALT_LAT_KERN : test_sirqlat ? COBALT_LAT_SIRQ :
+			test_ulat ? COBALT_LAT_USER :
+			COBALT_LAT_LAST + test_gpiolat;
+		do_measurement(type);
+	} else {
+		if (verbosity)
+			printf("== latmus started for core tuning, "
+			       "period=%d microseconds (may take a while)\n",
+			       period_usecs);
+
+		if (test_irqlat)
+			do_tuning(COBALT_LAT_IRQ);
+
+		if (test_klat)
+			do_tuning(COBALT_LAT_KERN);
+
+		if (test_ulat)
+			do_tuning(COBALT_LAT_USER);
+
+		if (verbosity)
+			printf("== tuning completed after %ds\n",
+			       (int)(time(NULL) - start_time));
+	}
+
+	return 0;
+}
-- 
2.17.1