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
checkpris(int sched)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 */
try_anyway(const char * s)89 static void try_anyway(const char *s)
90 {
91 fputs(s, stderr);
92 fprintf(stderr, "(trying anyway)\n");
93 errno = 0;
94 }
95
q(int line,int code,const char * text)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
sched(int ac,char * av[])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
main(int argc,char * argv[])292 int main(int argc, char *argv[]) { return sched(argc, argv); }
293 #endif
294