2 * SPDX-License-Identifier: BSD-4-Clause
4 * Copyright (c) 1996 - 2000
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36 #include <sys/types.h>
49 #define CAN_USE_ALARMS
58 /* Fifo: Verify that fifo and round-robin scheduling seem to work.
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.
67 static void tidyup(void)
74 tvsub(const struct timeval *a, const struct timeval *b)
79 sdiff = a->tv_sec - b->tv_sec;
80 udiff = a->tv_usec - b->tv_usec;
82 return (double)(sdiff * 1000000 + udiff) / 1e6;
85 int fifo(int argc, char *argv[])
88 volatile long *p, pid;
90 struct sched_param fifo_param;
91 struct timespec interval;
93 struct timeval ranat[MAX_RANAT];
96 static struct itimerval itimerval;
99 /* What is the round robin interval?
102 if (sched_rr_get_interval(0, &interval) == -1) {
103 perror("sched_rr_get_interval");
107 #ifdef CAN_USE_ALARMS
108 signal(SIGALRM, tick);
111 fifo_param.sched_priority = 1;
113 p = (long *)mmap(0, sizeof(*p),
114 PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, -1, 0);
121 if (sched_setscheduler(0, SCHED_FIFO, &fifo_param) == -1)
123 perror("sched_setscheduler");
129 if ((child = fork()) == 0)
131 /* Child process. Just keep setting the pointer to our
132 * PID. The parent will kill us when it wants to.
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.
152 itimerval.it_value.tv_usec = interval.tv_nsec / (1000 / 250);
154 itimerval.it_value.tv_sec = itimerval.it_value.tv_usec / 1000000;
155 itimerval.it_value.tv_usec %= 1000000;
158 if (setitimer(ITIMER_REAL, &itimerval, 0) == -1) {
165 gettimeofday(ranat, 0);
167 while (!ticked && i < MAX_RANAT)
169 gettimeofday(ranat + i, 0);
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));
187 /* Switch to the round robin scheduler and the child
188 * should run within twice the interval.
190 if (sched_setscheduler(child, SCHED_RR, &fifo_param) == -1 ||
191 sched_setscheduler(0, SCHED_RR, &fifo_param) == -1)
193 perror("sched_setscheduler");
201 #ifdef CAN_USE_ALARMS
203 /* Now we do want to see it run. But only set
204 * the alarm for twice the interval:
206 itimerval.it_value.tv_usec = interval.tv_nsec / 500;
208 if (setitimer(ITIMER_REAL, &itimerval, 0) == -1) {
214 for (i = 0; !ticked; i++)
221 fprintf(stderr,"Child never ran when it should have.\n");
227 #ifdef STANDALONE_TESTS
228 int main(int argc, char *argv[]) { return fifo(argc, argv); }