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31 * $FreeBSD: src/tools/regression/p1003_1b/yield.c,v 1.1 2000/02/16 14:28:42 dufault Exp $
32 * $DragonFly: src/tools/regression/p1003_1b/yield.c,v 1.2 2003/06/17 04:29:11 dillon Exp $
35 #include <sys/types.h>
42 #include <sys/types.h>
50 /* buzz: busy wait a random amount of time.
52 static void buzz(int n)
55 int m = random() & 0x0ffff;
56 for (i = 0; i < m; i++)
60 /* Yield: Verify that "sched_yield" works for the FIFO case.
61 * This runs several processes and verifies that the yield seems
62 * to permit the next one on the ready queue to run.
64 int yield(int argc, char *argv[])
70 pid_t youngest = !0; /* Our youngest child */
71 struct sched_param set, got;
76 set.sched_priority = sched_get_priority_max(SCHED_FIFO);
77 if (set.sched_priority == -1 && errno) {
78 perror("sched_get_priority_max");
86 fprintf(stderr, "Usage: prog [n_instances]\n");
90 n = nslaves = atoi(argv[1]);
92 p = (int *)mmap(0, sizeof(int),
93 PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED|MAP_INHERIT, -1, 0);
100 if (sched_setscheduler(0, SCHED_FIFO, &set) == -1)
101 err(errno, "sched_setscheduler");
103 /* I better still be SCHED_FIFO and RT_PRIO_MAX:
105 (void)sched_is(__LINE__, &got, SCHED_FIFO);
106 if (got.sched_priority != set.sched_priority) {
107 fprintf(stderr, "line %d: scheduler screwup\n",
115 /* Fork off the slaves.
117 for (i = 0; i < nslaves; i++) {
118 if ((youngest = fork()) == 0) {
119 /* I better still be SCHED_FIFO and RT_PRIO_MAX:
121 (void)sched_is(__LINE__, &got, SCHED_FIFO);
123 if (got.sched_priority != set.sched_priority) {
124 fprintf(stderr, "line %d: scheduler screwup\n",
129 master = 0; /* I'm a slave */
130 slave = i + 1; /* With this flag */
131 *p = slave; /* And I live */
137 /* If we conform the slave processes haven't run yet.
138 * The master must yield to let the first slave run.
142 "Error at line %d: Writer %d has run\n", __LINE__, *p);
147 /* Now the master yields, the first slave runs, and yields,
148 * next runs, yields, ...
150 * So the master should get through this first.
153 if (sched_yield() == -1)
154 err(errno, "sched_yield");
159 /* The final slave process should be the last one started.
163 "Error at line %d: Final slave is %d not %d.\n",
164 __LINE__, *p, nslaves);
168 /* Wait for our youngest to exit:
170 waitpid(youngest, &status, 0);
172 exit(WEXITSTATUS(status)); /* Let the slaves continue */
175 /* Now the first one has started up.
177 for (i = 0; i < nloops; i++) {
178 if (((*p) % nslaves) !=
179 ((slave + nslaves - 1) % nslaves)) {
180 fprintf(stderr, "%d ran before %d on iteration %d.\n",
186 /* Delay some random amount of time.
190 if (sched_yield() == -1)
191 err(errno, "sched_yield");
196 #ifdef STANDALONE_TESTS
197 int main(int argc, char *argv[]) { return yield(argc, argv); }