/*-
* SPDX-License-Identifier: BSD-4-Clause
*
* Copyright (c) 1996-1999
* HD Associates, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by HD Associates, Inc
* 4. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY HD ASSOCIATES AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL HD ASSOCIATES OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*/
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <err.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sched.h>
#include <stdlib.h>
#include <sys/wait.h>
#include "prutil.h"
/* buzz: busy wait a random amount of time.
*/
static void buzz(int n)
{
volatile int i;
int m = random() & 0x0ffff;
for (i = 0; i < m; i++)
;
}
/* Yield: Verify that "sched_yield" works for the FIFO case.
* This runs several processes and verifies that the yield seems
* to permit the next one on the ready queue to run.
*/
int yield(int argc, char *argv[])
{
volatile int *p;
int i;
int nslaves, n;
int master, slave;
pid_t youngest = !0; /* Our youngest child */
struct sched_param set, got;
int nloops = 1000;
errno = 0;
set.sched_priority = sched_get_priority_max(SCHED_FIFO);
if (set.sched_priority == -1 && errno) {
perror("sched_get_priority_max");
exit(errno);
}
if (argc == 1)
n = nslaves = 10;
else if (argc != 2) {
fprintf(stderr, "usage: prog [n_instances]\n");
exit(-1);
}
else
n = nslaves = atoi(argv[1]);
p = (int *)mmap(0, sizeof(int),
PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, -1, 0);
if (p == (int *)-1)
err(errno, "mmap");
*p = 0;
if (sched_setscheduler(0, SCHED_FIFO, &set) == -1)
err(errno, "sched_setscheduler");
/* I better still be SCHED_FIFO and RT_PRIO_MAX:
*/
(void)sched_is(__LINE__, &got, SCHED_FIFO);
if (got.sched_priority != set.sched_priority) {
fprintf(stderr, "line %d: scheduler screwup\n",
__LINE__);
exit(-1);
}
slave = 0;
master = 1;
/* Fork off the slaves.
*/
for (i = 0; i < nslaves; i++) {
if ((youngest = fork()) == 0) {
/* I better still be SCHED_FIFO and RT_PRIO_MAX:
*/
(void)sched_is(__LINE__, &got, SCHED_FIFO);
if (got.sched_priority != set.sched_priority) {
fprintf(stderr, "line %d: scheduler screwup\n",
__LINE__);
exit(-1);
}
master = 0; /* I'm a slave */
slave = i + 1; /* With this flag */
*p = slave; /* And I live */
break;
}
}
if (master) {
/* If we conform the slave processes haven't run yet.
* The master must yield to let the first slave run.
*/
if (*p != 0) {
fprintf(stderr,
"Error at line %d: Writer %d has run\n", __LINE__, *p);
exit(-1);
}
}
/* Now the master yields, the first slave runs, and yields,
* next runs, yields, ...
*
* So the master should get through this first.
*/
if (sched_yield() == -1)
err(errno, "sched_yield");
if (master) {
int status;
/* The final slave process should be the last one started.
*/
if (*p != nslaves) {
fprintf(stderr,
"Error at line %d: Final slave is %d not %d.\n",
__LINE__, *p, nslaves);
exit(-1);
}
/* Wait for our youngest to exit:
*/
waitpid(youngest, &status, 0);
exit(WEXITSTATUS(status)); /* Let the slaves continue */
}
/* Now the first one has started up.
*/
for (i = 0; i < nloops; i++) {
if (((*p) % nslaves) !=
((slave + nslaves - 1) % nslaves)) {
fprintf(stderr, "%d ran before %d on iteration %d.\n",
*p, slave, i);
exit(-1);
}
*p = slave;
/* Delay some random amount of time.
*/
buzz(slave);
if (sched_yield() == -1)
err(errno, "sched_yield");
}
exit(0);
}
#ifdef STANDALONE_TESTS
int main(int argc, char *argv[]) { return yield(argc, argv); }
#endif
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