selftests/timers: Add mqueue latency test from the timetest suite

Add test to validate mqueue timeout latency from the timetest suite

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

···
 CFLAGS += -O3 -Wl,-no-as-needed -Wall $(BUILD_FLAGS)
 LDFLAGS += -lrt -lpthread
 bins = posix_timers nanosleep inconsistency-check nsleep-lat raw_skew \
-	set-timer-lat threadtest
+	set-timer-lat threadtest mqueue-lat
 
 all: ${bins}
 
···
 	./nanosleep
 	./nsleep-lat
 	./set-timer-lat
+	./mqueue-lat
 	./inconsistency-check
 	./raw_skew
 	./threadtest -t 30 -n 8

tools/testing/selftests/timers/mqueue-lat.c

···
+/* Measure mqueue timeout latency
+ *              by: john stultz ([e-mail])
+ *		(C) Copyright Linaro 2013
+ *
+ *		Inspired with permission from example test by:
+ *			Romain Francoise <[e-mail]>
+ *              Licensed under the GPLv2
+ *
+ *  To build:
+ *	$ gcc mqueue-lat.c -o mqueue-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 <stdlib.h>
+#include <time.h>
+#include <sys/time.h>
+#include <sys/timex.h>
+#include <string.h>
+#include <signal.h>
+#include <errno.h>
+#include <mqueue.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 NSEC_PER_SEC 1000000000ULL
+
+#define TARGET_TIMEOUT		100000000	/* 100ms in nanoseconds */
+#define UNRESONABLE_LATENCY	40000000	/* 40ms in nanosecs */
+
+
+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;
+}
+
+struct timespec timespec_add(struct timespec ts, unsigned long long ns)
+{
+	ts.tv_nsec += ns;
+	while (ts.tv_nsec >= NSEC_PER_SEC) {
+		ts.tv_nsec -= NSEC_PER_SEC;
+		ts.tv_sec++;
+	}
+	return ts;
+}
+
+int mqueue_lat_test(void)
+{
+
+	mqd_t q;
+	struct mq_attr attr;
+	struct timespec start, end, now, target;
+	int i, count, ret;
+
+	q = mq_open("/foo", O_CREAT | O_RDONLY, 0666, NULL);
+	if (q < 0) {
+		perror("mq_open");
+		return -1;
+	}
+	mq_getattr(q, &attr);
+
+
+	count = 100;
+	clock_gettime(CLOCK_MONOTONIC, &start);
+
+	for (i = 0; i < count; i++) {
+		char buf[attr.mq_msgsize];
+
+		clock_gettime(CLOCK_REALTIME, &now);
+		target = now;
+		target = timespec_add(now, TARGET_TIMEOUT); /* 100ms */
+
+		ret = mq_timedreceive(q, buf, sizeof(buf), NULL, &target);
+		if (ret < 0 && errno != ETIMEDOUT) {
+			perror("mq_timedreceive");
+			return -1;
+		}
+	}
+	clock_gettime(CLOCK_MONOTONIC, &end);
+
+	mq_close(q);
+
+	if ((timespec_sub(start, end)/count) > TARGET_TIMEOUT + UNRESONABLE_LATENCY)
+		return -1;
+
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	int ret;
+
+	printf("Mqueue latency :                          ");
+
+	ret = mqueue_lat_test();
+	if (ret < 0) {
+		printf("[FAILED]\n");
+		return ksft_exit_fail();
+	}
+	printf("[OK]\n");
+	return ksft_exit_pass();
+}