1 /*- 2 * SPDX-License-Identifier: BSD-4-Clause 3 * 4 * Copyright (c) 1996 - 2000 5 * HD Associates, Inc. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by HD Associates, Inc 18 * 4. Neither the name of the author nor the names of any co-contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY HD ASSOCIATES AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL HD ASSOCIATES OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * $FreeBSD$ 35 */ 36 #include <sys/types.h> 37 #include <sys/mman.h> 38 #include <sys/time.h> 39 #include <err.h> 40 #include <errno.h> 41 #include <fcntl.h> 42 #include <sched.h> 43 #include <signal.h> 44 #include <stdlib.h> 45 #include <stdio.h> 46 #include <unistd.h> 47 48 volatile int ticked; 49 #define CAN_USE_ALARMS 50 51 #ifdef CAN_USE_ALARMS 52 void tick(int arg) 53 { 54 ticked = 1; 55 } 56 #endif 57 58 /* Fifo: Verify that fifo and round-robin scheduling seem to work. 59 * 60 * This tests: 61 * 1. That sched_rr_get_interval seems to work; 62 * 2. That FIFO scheduling doesn't seeem to be round-robin; 63 * 3. That round-robin scheduling seems to work. 64 * 65 */ 66 static pid_t child; 67 static void tidyup(void) 68 { 69 if (child) 70 kill(child, SIGHUP); 71 } 72 73 static double 74 tvsub(const struct timeval *a, const struct timeval *b) 75 { 76 long sdiff; 77 long udiff; 78 79 sdiff = a->tv_sec - b->tv_sec; 80 udiff = a->tv_usec - b->tv_usec; 81 82 return (double)(sdiff * 1000000 + udiff) / 1e6; 83 } 84 85 int fifo(int argc, char *argv[]) 86 { 87 int e = 0; 88 volatile long *p, pid; 89 int i; 90 struct sched_param fifo_param; 91 struct timespec interval; 92 #define MAX_RANAT 32 93 struct timeval ranat[MAX_RANAT]; 94 95 #ifdef CAN_USE_ALARMS 96 static struct itimerval itimerval; 97 #endif 98 99 /* What is the round robin interval? 100 */ 101 102 if (sched_rr_get_interval(0, &interval) == -1) { 103 perror("sched_rr_get_interval"); 104 exit(errno); 105 } 106 107 #ifdef CAN_USE_ALARMS 108 signal(SIGALRM, tick); 109 #endif 110 111 fifo_param.sched_priority = 1; 112 113 p = (long *)mmap(0, sizeof(*p), 114 PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, -1, 0); 115 116 if (p == (long *)-1) 117 err(errno, "mmap"); 118 119 *p = 0; 120 121 if (sched_setscheduler(0, SCHED_FIFO, &fifo_param) == -1) 122 { 123 perror("sched_setscheduler"); 124 return -1; 125 } 126 127 pid = getpid(); 128 129 if ((child = fork()) == 0) 130 { 131 /* Child process. Just keep setting the pointer to our 132 * PID. The parent will kill us when it wants to. 133 */ 134 135 pid = getpid(); 136 while (1) 137 *p = pid; 138 } 139 else 140 { 141 atexit(tidyup); 142 *p = pid; 143 144 145 ticked = 0; 146 147 #ifdef CAN_USE_ALARMS 148 /* Set an alarm for 250 times the round-robin interval. 149 * Then we will verify that a similar priority process 150 * will not run when we are using the FIFO scheduler. 151 */ 152 itimerval.it_value.tv_usec = interval.tv_nsec / (1000 / 250); 153 154 itimerval.it_value.tv_sec = itimerval.it_value.tv_usec / 1000000; 155 itimerval.it_value.tv_usec %= 1000000; 156 157 158 if (setitimer(ITIMER_REAL, &itimerval, 0) == -1) { 159 perror("setitimer"); 160 exit(errno); 161 } 162 #endif 163 164 165 gettimeofday(ranat, 0); 166 i = 1; 167 while (!ticked && i < MAX_RANAT) 168 if (*p == child) { 169 gettimeofday(ranat + i, 0); 170 *p = 0; 171 e = -1; 172 i++; 173 } 174 175 if (e) { 176 int j; 177 178 fprintf(stderr, 179 "SCHED_FIFO had erroneous context switches:\n"); 180 for (j = 1; j < i; j++) { 181 fprintf(stderr, "%d %g\n", j, 182 tvsub(ranat + j, ranat + j - 1)); 183 } 184 return e; 185 } 186 187 /* Switch to the round robin scheduler and the child 188 * should run within twice the interval. 189 */ 190 if (sched_setscheduler(child, SCHED_RR, &fifo_param) == -1 || 191 sched_setscheduler(0, SCHED_RR, &fifo_param) == -1) 192 { 193 perror("sched_setscheduler"); 194 return -1; 195 } 196 197 e = -1; 198 199 ticked = 0; 200 201 #ifdef CAN_USE_ALARMS 202 203 /* Now we do want to see it run. But only set 204 * the alarm for twice the interval: 205 */ 206 itimerval.it_value.tv_usec = interval.tv_nsec / 500; 207 208 if (setitimer(ITIMER_REAL, &itimerval, 0) == -1) { 209 perror("setitimer"); 210 exit(errno); 211 } 212 #endif 213 214 for (i = 0; !ticked; i++) 215 if (*p == child) { 216 e = 0; 217 break; 218 } 219 220 if (e) 221 fprintf(stderr,"Child never ran when it should have.\n"); 222 } 223 224 exit(e); 225 } 226 227 #ifdef STANDALONE_TESTS 228 int main(int argc, char *argv[]) { return fifo(argc, argv); } 229 #endif 230