/* Measure mqueue timeout latency *              by: john stultz (john.stultz@linaro.org) *		(C) Copyright Linaro 2013 * *		Inspired with permission from example test by: *			Romain Francoise <romain@orebokech.com> *              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>#include "clock-helpers.h"#include "kselftest.h"  #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 :                          ");	fflush(stdout); 	ret = mqueue_lat_test();	if (ret < 0) {		printf("[FAILED]\n");		ksft_exit_fail();	}	printf("[OK]\n");	ksft_exit_pass();}