1 /*- 2 * SPDX-License-Identifier: BSD-4-Clause 3 * 4 * Copyright (c) 1996-1999 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 */ 35 36 /* XXX: The spec says that if _POSIX_C_SOURCE is defined then 37 * _POSIX_SOURCE is ignored. However, this is similar to 38 * the code in the O'Reilly "POSIX.4" book 39 */ 40 41 #define _POSIX_VERSION 199309L 42 #define _POSIX_SOURCE 43 #define _POSIX_C_SOURCE 199309L 44 45 #include <sys/mman.h> 46 #include <errno.h> 47 #include <fcntl.h> 48 #include <limits.h> 49 #include <sched.h> 50 #include <stdio.h> 51 #define __XSI_VISIBLE 1 52 #include <stdlib.h> 53 #undef __XSI_VISIBLE 54 #include <string.h> 55 #include <unistd.h> 56 57 #include "prutil.h" 58 59 static FILE *verbose; 60 61 static void 62 checkpris(int sched) 63 { 64 int smin; 65 int smax; 66 67 errno = 0; 68 69 if ( (smin = sched_get_priority_min(sched)) == -1 && errno) 70 quit("sched_get_priority_min"); 71 72 if ( (smax = sched_get_priority_max(sched)) == -1 && errno) 73 quit("sched_get_priority_max"); 74 75 if (smax - smin + 1 < 32 || smax < smin) { 76 fprintf(stderr, "Illegal priority range for %s: %d to %d\n", 77 sched_text(sched), smin, smax); 78 exit(-1); 79 } 80 81 if (verbose) 82 fprintf(verbose, "%12s: sched_min %2d sched_max %2d\n", 83 sched_text(sched), smin, smax); 84 } 85 86 /* Set "try_anyway" to quit if you don't want to go on when 87 * it doesn't look like something should work. 88 */ 89 static void try_anyway(const char *s) 90 { 91 fputs(s, stderr); 92 fprintf(stderr, "(trying anyway)\n"); 93 errno = 0; 94 } 95 96 static void q(int line, int code, const char *text) 97 { 98 if (code == -1) 99 { 100 fprintf(stderr, "Error at line %d:\n", line); 101 perror(text); 102 exit(errno); 103 } 104 } 105 106 int sched(int ac, char *av[]) 107 { 108 int fifo_schedmin, fifo_schedmax; 109 int i; 110 struct sched_param rt_param; 111 int n_instances = 10; 112 int sched; 113 114 verbose = 0; 115 116 #if _POSIX_VERSION < 199309 117 try_anyway("The _POSIX_VERSION predates P1003.1B\n"); 118 #endif 119 120 #if !defined(_POSIX_PRIORITY_SCHEDULING) 121 try_anyway( 122 "The environment does not claim to support Posix scheduling.\n"); 123 #endif 124 125 /* Is priority scheduling configured? 126 */ 127 errno = 0; 128 if (sysconf(_SC_PRIORITY_SCHEDULING) == -1) { 129 if (errno != 0) { 130 /* This isn't valid - may be a standard violation 131 */ 132 quit("(should not happen) sysconf(_SC_PRIORITY_SCHEDULING)"); 133 } 134 else { 135 try_anyway( 136 "The environment does not have run-time " 137 "support for Posix scheduling.\n"); 138 } 139 } 140 141 /* Check that the priorities seem reasonable. 142 */ 143 144 checkpris(SCHED_FIFO); 145 checkpris(SCHED_RR); 146 checkpris(SCHED_OTHER); 147 148 /* BSD extensions? 149 */ 150 #if defined(SCHED_IDLE) 151 checkpris(SCHED_IDLE); 152 #endif 153 154 fifo_schedmin = sched_get_priority_min(SCHED_FIFO); 155 fifo_schedmax = sched_get_priority_max(SCHED_FIFO); 156 157 /* Make sure we can do some basic schedule switching: 158 */ 159 { 160 struct sched_param orig_param, shouldbe; 161 int orig_scheduler = sched_is(__LINE__, &orig_param, -1); 162 163 if (verbose) 164 fprintf(verbose, 165 "The original scheduler is %s and the priority is %d.\n", 166 sched_text(orig_scheduler), orig_param.sched_priority); 167 168 /* Basic check: Try to set current settings: 169 */ 170 q(__LINE__, sched_setscheduler(0, orig_scheduler, &orig_param), 171 "sched_setscheduler: Can't set original scheduler"); 172 173 rt_param.sched_priority = fifo_schedmin; 174 175 q(__LINE__, sched_setscheduler(0, SCHED_FIFO, &rt_param), 176 "sched_setscheduler SCHED_FIFO"); 177 178 (void)sched_is(__LINE__, 0, SCHED_FIFO); 179 180 q(__LINE__, sched_getparam(0, &shouldbe), "sched_getparam"); 181 182 if (shouldbe.sched_priority != fifo_schedmin) 183 quit("sched_setscheduler wrong priority (min)"); 184 185 rt_param.sched_priority = fifo_schedmin; 186 187 q(__LINE__, sched_setparam(0, &rt_param), 188 "sched_setparam to fifo_schedmin"); 189 190 rt_param.sched_priority = fifo_schedmin + 1; 191 192 q(__LINE__, sched_setparam(0, &rt_param), 193 "sched_setparam to fifo_schedmin + 1"); 194 195 q(__LINE__, sched_getparam(0, &shouldbe), 196 "sched_getparam"); 197 198 if (shouldbe.sched_priority != fifo_schedmin + 1) 199 quit("sched_setscheduler wrong priority (min + 1)"); 200 201 q(__LINE__, sched_setscheduler(0, SCHED_RR, &rt_param), 202 "sched_setscheduler SCHED_RR"); 203 204 (void)sched_is(__LINE__, 0, SCHED_RR); 205 206 q(__LINE__, sched_setscheduler(0, orig_scheduler, &orig_param), 207 "sched_setscheduler restoring original scheduler"); 208 209 (void)sched_is(__LINE__, 0, orig_scheduler); 210 } 211 212 213 { 214 char nam[] = "P1003_1b_schedXXXXXX"; 215 int fd; 216 pid_t p; 217 pid_t *lastrun; 218 219 fd = mkstemp(nam); 220 if (fd == -1) 221 q(__LINE__, errno, "mkstemp failed"); 222 223 (void)unlink(nam); 224 225 p = (pid_t)0; 226 227 write(fd, &p, sizeof(p)); 228 229 q(__LINE__, (int)(lastrun = mmap(0, sizeof(*lastrun), PROT_READ|PROT_WRITE, 230 MAP_SHARED, fd, 0)), "mmap"); 231 232 /* Set our priority at the highest: 233 */ 234 sched = SCHED_FIFO; 235 rt_param.sched_priority = fifo_schedmax; 236 q(__LINE__, sched_setscheduler(0, sched, &rt_param), 237 "sched_setscheduler sched"); 238 239 for (i = 0; i < n_instances; i++) 240 { 241 pid_t me; 242 243 /* XXX This is completely bogus. The children never run. 244 */ 245 if ((me = fork()) != 0) 246 { 247 /* Parent. 248 */ 249 (void)sched_is(__LINE__, 0, sched); 250 251 /* Lower our priority: 252 */ 253 rt_param.sched_priority--; 254 255 q(__LINE__, sched_setscheduler(0, sched, &rt_param), 256 "sched_setscheduler sched"); 257 258 while (1) 259 { 260 q(__LINE__, sched_getparam(0, &rt_param), "sched_getparam"); 261 262 rt_param.sched_priority--; 263 264 265 if (rt_param.sched_priority < fifo_schedmin) 266 exit(0); 267 268 *lastrun = me; 269 q(__LINE__, sched_setparam(0, &rt_param), "sched_setparam"); 270 271 if (*lastrun == me) 272 { 273 /* The child will run twice 274 * at the end: 275 */ 276 if (!me || rt_param.sched_priority != 0) 277 { 278 fprintf(stderr, 279 "ran process %ld twice at priority %d\n", 280 (long)me, rt_param.sched_priority + 1); 281 exit(-1); 282 } 283 } 284 } 285 } 286 } 287 } 288 289 return 0; 290 } 291 #ifdef STANDALONE_TESTS 292 int main(int argc, char *argv[]) { return sched(argc, argv); } 293 #endif 294