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
48volatile int ticked;
49#define CAN_USE_ALARMS
50
51#ifdef CAN_USE_ALARMS
52void 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 */
66static pid_t child;
67static void tidyup(void)
68{
69	if (child)
70		kill(child, SIGHUP);
71}
72
73static double
74tvsub(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
85int 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
228int main(int argc, char *argv[]) { return fifo(argc, argv); }
229#endif
230