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 * $FreeBSD$
34 *
35 */
36 #include <sys/types.h>
37 #include <unistd.h>
38 #include <stdlib.h>
39 #include <stdio.h>
40 #include <errno.h>
41 #include <err.h>
42 #include <fcntl.h>
43 #include <sys/types.h>
44 #include <sys/mman.h>
45 #include <sched.h>
46 #include <stdlib.h>
47 #include <sys/wait.h>
48
49 #include "prutil.h"
50
51 /* buzz: busy wait a random amount of time.
52 */
buzz(int n)53 static void buzz(int n)
54 {
55 volatile int i;
56 int m = random() & 0x0ffff;
57 for (i = 0; i < m; i++)
58 ;
59 }
60
61 /* Yield: Verify that "sched_yield" works for the FIFO case.
62 * This runs several processes and verifies that the yield seems
63 * to permit the next one on the ready queue to run.
64 */
yield(int argc,char * argv[])65 int yield(int argc, char *argv[])
66 {
67 volatile int *p;
68 int i;
69 int nslaves, n;
70 int master, slave;
71 pid_t youngest = !0; /* Our youngest child */
72 struct sched_param set, got;
73 int nloops = 1000;
74
75 errno = 0;
76
77 set.sched_priority = sched_get_priority_max(SCHED_FIFO);
78 if (set.sched_priority == -1 && errno) {
79 perror("sched_get_priority_max");
80 exit(errno);
81 }
82
83 if (argc == 1)
84 n = nslaves = 10;
85
86 else if (argc != 2) {
87 fprintf(stderr, "usage: prog [n_instances]\n");
88 exit(-1);
89 }
90 else
91 n = nslaves = atoi(argv[1]);
92
93 p = (int *)mmap(0, sizeof(int),
94 PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, -1, 0);
95
96 if (p == (int *)-1)
97 err(errno, "mmap");
98
99 *p = 0;
100
101 if (sched_setscheduler(0, SCHED_FIFO, &set) == -1)
102 err(errno, "sched_setscheduler");
103
104 /* I better still be SCHED_FIFO and RT_PRIO_MAX:
105 */
106 (void)sched_is(__LINE__, &got, SCHED_FIFO);
107 if (got.sched_priority != set.sched_priority) {
108 fprintf(stderr, "line %d: scheduler screwup\n",
109 __LINE__);
110 exit(-1);
111 }
112
113 slave = 0;
114 master = 1;
115
116 /* Fork off the slaves.
117 */
118 for (i = 0; i < nslaves; i++) {
119 if ((youngest = fork()) == 0) {
120 /* I better still be SCHED_FIFO and RT_PRIO_MAX:
121 */
122 (void)sched_is(__LINE__, &got, SCHED_FIFO);
123
124 if (got.sched_priority != set.sched_priority) {
125 fprintf(stderr, "line %d: scheduler screwup\n",
126 __LINE__);
127 exit(-1);
128 }
129
130 master = 0; /* I'm a slave */
131 slave = i + 1; /* With this flag */
132 *p = slave; /* And I live */
133 break;
134 }
135 }
136
137 if (master) {
138 /* If we conform the slave processes haven't run yet.
139 * The master must yield to let the first slave run.
140 */
141 if (*p != 0) {
142 fprintf(stderr,
143 "Error at line %d: Writer %d has run\n", __LINE__, *p);
144 exit(-1);
145 }
146 }
147
148 /* Now the master yields, the first slave runs, and yields,
149 * next runs, yields, ...
150 *
151 * So the master should get through this first.
152 */
153
154 if (sched_yield() == -1)
155 err(errno, "sched_yield");
156
157 if (master) {
158 int status;
159
160 /* The final slave process should be the last one started.
161 */
162 if (*p != nslaves) {
163 fprintf(stderr,
164 "Error at line %d: Final slave is %d not %d.\n",
165 __LINE__, *p, nslaves);
166 exit(-1);
167 }
168
169 /* Wait for our youngest to exit:
170 */
171 waitpid(youngest, &status, 0);
172
173 exit(WEXITSTATUS(status)); /* Let the slaves continue */
174 }
175
176 /* Now the first one has started up.
177 */
178 for (i = 0; i < nloops; i++) {
179 if (((*p) % nslaves) !=
180 ((slave + nslaves - 1) % nslaves)) {
181 fprintf(stderr, "%d ran before %d on iteration %d.\n",
182 *p, slave, i);
183 exit(-1);
184 }
185 *p = slave;
186
187 /* Delay some random amount of time.
188 */
189 buzz(slave);
190
191 if (sched_yield() == -1)
192 err(errno, "sched_yield");
193 }
194
195 exit(0);
196 }
197 #ifdef STANDALONE_TESTS
main(int argc,char * argv[])198 int main(int argc, char *argv[]) { return yield(argc, argv); }
199 #endif
200