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 #include <sys/types.h>
35 #include <sys/mman.h>
36 #include <sys/time.h>
37 #include <err.h>
38 #include <errno.h>
39 #include <fcntl.h>
40 #include <sched.h>
41 #include <signal.h>
42 #include <stdlib.h>
43 #include <stdio.h>
44 #include <unistd.h>
45
46 volatile int ticked;
47 #define CAN_USE_ALARMS
48
49 #ifdef CAN_USE_ALARMS
tick(int arg)50 void tick(int arg)
51 {
52 ticked = 1;
53 }
54 #endif
55
56 /* Fifo: Verify that fifo and round-robin scheduling seem to work.
57 *
58 * This tests:
59 * 1. That sched_rr_get_interval seems to work;
60 * 2. That FIFO scheduling doesn't seeem to be round-robin;
61 * 3. That round-robin scheduling seems to work.
62 *
63 */
64 static pid_t child;
tidyup(void)65 static void tidyup(void)
66 {
67 if (child)
68 kill(child, SIGHUP);
69 }
70
71 static double
tvsub(const struct timeval * a,const struct timeval * b)72 tvsub(const struct timeval *a, const struct timeval *b)
73 {
74 long sdiff;
75 long udiff;
76
77 sdiff = a->tv_sec - b->tv_sec;
78 udiff = a->tv_usec - b->tv_usec;
79
80 return (double)(sdiff * 1000000 + udiff) / 1e6;
81 }
82
fifo(int argc,char * argv[])83 int fifo(int argc, char *argv[])
84 {
85 int e = 0;
86 volatile long *p, pid;
87 int i;
88 struct sched_param fifo_param;
89 struct timespec interval;
90 #define MAX_RANAT 32
91 struct timeval ranat[MAX_RANAT];
92
93 #ifdef CAN_USE_ALARMS
94 static struct itimerval itimerval;
95 #endif
96
97 /* What is the round robin interval?
98 */
99
100 if (sched_rr_get_interval(0, &interval) == -1) {
101 perror("sched_rr_get_interval");
102 exit(errno);
103 }
104
105 #ifdef CAN_USE_ALARMS
106 signal(SIGALRM, tick);
107 #endif
108
109 fifo_param.sched_priority = 1;
110
111 p = (long *)mmap(0, sizeof(*p),
112 PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, -1, 0);
113
114 if (p == (long *)-1)
115 err(errno, "mmap");
116
117 *p = 0;
118
119 if (sched_setscheduler(0, SCHED_FIFO, &fifo_param) == -1)
120 {
121 perror("sched_setscheduler");
122 return -1;
123 }
124
125 pid = getpid();
126
127 if ((child = fork()) == 0)
128 {
129 /* Child process. Just keep setting the pointer to our
130 * PID. The parent will kill us when it wants to.
131 */
132
133 pid = getpid();
134 while (1)
135 *p = pid;
136 }
137 else
138 {
139 atexit(tidyup);
140 *p = pid;
141
142
143 ticked = 0;
144
145 #ifdef CAN_USE_ALARMS
146 /* Set an alarm for 250 times the round-robin interval.
147 * Then we will verify that a similar priority process
148 * will not run when we are using the FIFO scheduler.
149 */
150 itimerval.it_value.tv_usec = interval.tv_nsec / (1000 / 250);
151
152 itimerval.it_value.tv_sec = itimerval.it_value.tv_usec / 1000000;
153 itimerval.it_value.tv_usec %= 1000000;
154
155
156 if (setitimer(ITIMER_REAL, &itimerval, 0) == -1) {
157 perror("setitimer");
158 exit(errno);
159 }
160 #endif
161
162
163 gettimeofday(ranat, 0);
164 i = 1;
165 while (!ticked && i < MAX_RANAT)
166 if (*p == child) {
167 gettimeofday(ranat + i, 0);
168 *p = 0;
169 e = -1;
170 i++;
171 }
172
173 if (e) {
174 int j;
175
176 fprintf(stderr,
177 "SCHED_FIFO had erroneous context switches:\n");
178 for (j = 1; j < i; j++) {
179 fprintf(stderr, "%d %g\n", j,
180 tvsub(ranat + j, ranat + j - 1));
181 }
182 return e;
183 }
184
185 /* Switch to the round robin scheduler and the child
186 * should run within twice the interval.
187 */
188 if (sched_setscheduler(child, SCHED_RR, &fifo_param) == -1 ||
189 sched_setscheduler(0, SCHED_RR, &fifo_param) == -1)
190 {
191 perror("sched_setscheduler");
192 return -1;
193 }
194
195 e = -1;
196
197 ticked = 0;
198
199 #ifdef CAN_USE_ALARMS
200
201 /* Now we do want to see it run. But only set
202 * the alarm for twice the interval:
203 */
204 itimerval.it_value.tv_usec = interval.tv_nsec / 500;
205
206 if (setitimer(ITIMER_REAL, &itimerval, 0) == -1) {
207 perror("setitimer");
208 exit(errno);
209 }
210 #endif
211
212 for (i = 0; !ticked; i++)
213 if (*p == child) {
214 e = 0;
215 break;
216 }
217
218 if (e)
219 fprintf(stderr,"Child never ran when it should have.\n");
220 }
221
222 exit(e);
223 }
224
225 #ifdef STANDALONE_TESTS
main(int argc,char * argv[])226 int main(int argc, char *argv[]) { return fifo(argc, argv); }
227 #endif
228