selftests/timers: Add set-timer-lat test from timetest suite

Add my set-timer-lat test from the timetest suite. This
test checks the latency from set_timer and reports if
any are unreasonable (>40ms).

Cc: Shuah Khan <[e-mail]>
Cc: Prarit Bhargava <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Richard Cochran <[e-mail]>
Signed-off-by: John Stultz <[e-mail]>
Tested-by: Prarit Bhargava <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/testing/selftests/timers/Makefile

···
 BUILD_FLAGS = -DKTEST
 CFLAGS += -O3 -Wl,-no-as-needed -Wall $(BUILD_FLAGS)
 LDFLAGS += -lrt -lpthread
-bins = posix_timers nanosleep inconsistency-check nsleep-lat raw_skew
+bins = posix_timers nanosleep inconsistency-check nsleep-lat raw_skew \
+	set-timer-lat
 
 all: ${bins}
 
···
 	./posix_timers
 	./nanosleep
 	./nsleep-lat
+	./set-timer-lat
 	./inconsistency-check
 	./raw_skew
+
 clean:
 	rm -f ${bins}

tools/testing/selftests/timers/set-timer-lat.c

···
+/* set_timer latency test
+ *		John Stultz ([e-mail])
+ *              (C) Copyright Linaro 2014
+ *              Licensed under the GPLv2
+ *
+ *   This test makes sure the set_timer api is correct
+ *
+ *  To build:
+ *	$ gcc set-timer-lat.c -o set-timer-lat -lrt
+ *
+ *   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.
+ */
+
+
+#include <stdio.h>
+#include <unistd.h>
+#include <time.h>
+#include <string.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <pthread.h>
+#ifdef KTEST
+#include "../kselftest.h"
+#else
+static inline int ksft_exit_pass(void)
+{
+	exit(0);
+}
+static inline int ksft_exit_fail(void)
+{
+	exit(1);
+}
+#endif
+
+#define CLOCK_REALTIME			0
+#define CLOCK_MONOTONIC			1
+#define CLOCK_PROCESS_CPUTIME_ID	2
+#define CLOCK_THREAD_CPUTIME_ID		3
+#define CLOCK_MONOTONIC_RAW		4
+#define CLOCK_REALTIME_COARSE		5
+#define CLOCK_MONOTONIC_COARSE		6
+#define CLOCK_BOOTTIME			7
+#define CLOCK_REALTIME_ALARM		8
+#define CLOCK_BOOTTIME_ALARM		9
+#define CLOCK_HWSPECIFIC		10
+#define CLOCK_TAI			11
+#define NR_CLOCKIDS			12
+
+
+#define NSEC_PER_SEC 1000000000ULL
+#define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
+
+#define TIMER_SECS 3
+int alarmcount;
+int clock_id;
+struct timespec start_time;
+long long max_latency_ns;
+
+char *clockstring(int clockid)
+{
+	switch (clockid) {
+	case CLOCK_REALTIME:
+		return "CLOCK_REALTIME";
+	case CLOCK_MONOTONIC:
+		return "CLOCK_MONOTONIC";
+	case CLOCK_PROCESS_CPUTIME_ID:
+		return "CLOCK_PROCESS_CPUTIME_ID";
+	case CLOCK_THREAD_CPUTIME_ID:
+		return "CLOCK_THREAD_CPUTIME_ID";
+	case CLOCK_MONOTONIC_RAW:
+		return "CLOCK_MONOTONIC_RAW";
+	case CLOCK_REALTIME_COARSE:
+		return "CLOCK_REALTIME_COARSE";
+	case CLOCK_MONOTONIC_COARSE:
+		return "CLOCK_MONOTONIC_COARSE";
+	case CLOCK_BOOTTIME:
+		return "CLOCK_BOOTTIME";
+	case CLOCK_REALTIME_ALARM:
+		return "CLOCK_REALTIME_ALARM";
+	case CLOCK_BOOTTIME_ALARM:
+		return "CLOCK_BOOTTIME_ALARM";
+	case CLOCK_TAI:
+		return "CLOCK_TAI";
+	};
+	return "UNKNOWN_CLOCKID";
+}
+
+
+long long timespec_sub(struct timespec a, struct timespec b)
+{
+	long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
+
+	ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
+	return ret;
+}
+
+
+void sigalarm(int signo)
+{
+	long long delta_ns;
+	struct timespec ts;
+
+	clock_gettime(clock_id, &ts);
+	alarmcount++;
+
+	delta_ns = timespec_sub(start_time, ts);
+	delta_ns -= NSEC_PER_SEC * TIMER_SECS * alarmcount;
+
+	if (delta_ns < 0)
+		printf("%s timer fired early: FAIL\n", clockstring(clock_id));
+
+	if (delta_ns > max_latency_ns)
+		max_latency_ns = delta_ns;
+}
+
+int do_timer(int clock_id, int flags)
+{
+	struct sigevent se;
+	timer_t tm1;
+	struct itimerspec its1, its2;
+	int err;
+
+	/* Set up timer: */
+	memset(&se, 0, sizeof(se));
+	se.sigev_notify = SIGEV_SIGNAL;
+	se.sigev_signo = SIGRTMAX;
+	se.sigev_value.sival_int = 0;
+
+	max_latency_ns = 0;
+	alarmcount = 0;
+
+	err = timer_create(clock_id, &se, &tm1);
+	if (err) {
+		printf("%s - timer_create() failed\n", clockstring(clock_id));
+		return -1;
+	}
+
+	clock_gettime(clock_id, &start_time);
+	if (flags) {
+		its1.it_value = start_time;
+		its1.it_value.tv_sec += TIMER_SECS;
+	} else {
+		its1.it_value.tv_sec = TIMER_SECS;
+		its1.it_value.tv_nsec = 0;
+	}
+	its1.it_interval.tv_sec = TIMER_SECS;
+	its1.it_interval.tv_nsec = 0;
+
+	err = timer_settime(tm1, flags, &its1, &its2);
+	if (err) {
+		printf("%s - timer_settime() failed\n", clockstring(clock_id));
+		return -1;
+	}
+
+	while (alarmcount < 5)
+		sleep(1);
+
+	printf("%-22s %s max latency: %10lld ns : ",
+			clockstring(clock_id),
+			flags ? "ABSTIME":"RELTIME",
+			max_latency_ns);
+
+	timer_delete(tm1);
+	if (max_latency_ns < UNRESONABLE_LATENCY) {
+		printf("[OK]\n");
+		return 0;
+	}
+	printf("[FAILED]\n");
+	return -1;
+}
+
+int main(void)
+{
+	struct sigaction act;
+	int signum = SIGRTMAX;
+	int ret = 0;
+
+	/* Set up signal handler: */
+	sigfillset(&act.sa_mask);
+	act.sa_flags = 0;
+	act.sa_handler = sigalarm;
+	sigaction(signum, &act, NULL);
+
+	printf("Setting timers for every %i seconds\n", TIMER_SECS);
+	for (clock_id = 0; clock_id < NR_CLOCKIDS; clock_id++) {
+
+		if ((clock_id == CLOCK_PROCESS_CPUTIME_ID) ||
+				(clock_id == CLOCK_THREAD_CPUTIME_ID) ||
+				(clock_id == CLOCK_MONOTONIC_RAW) ||
+				(clock_id == CLOCK_REALTIME_COARSE) ||
+				(clock_id == CLOCK_MONOTONIC_COARSE) ||
+				(clock_id == CLOCK_HWSPECIFIC))
+			continue;
+
+		ret |= do_timer(clock_id, TIMER_ABSTIME);
+		ret |= do_timer(clock_id, 0);
+	}
+	if (ret)
+		return ksft_exit_fail();
+	return ksft_exit_pass();
+}