/*-
* SPDX-License-Identifier: BSD-4-Clause
*
* Copyright (c) 1996 - 2000
* 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 <sys/mman.h>
#include <sys/time.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <sched.h>
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
volatile int ticked;
#define CAN_USE_ALARMS
#ifdef CAN_USE_ALARMS
void tick(int arg)
{
ticked = 1;
}
#endif
/* Fifo: Verify that fifo and round-robin scheduling seem to work.
*
* This tests:
* 1. That sched_rr_get_interval seems to work;
* 2. That FIFO scheduling doesn't seeem to be round-robin;
* 3. That round-robin scheduling seems to work.
*
*/
static pid_t child;
static void tidyup(void)
{
if (child)
kill(child, SIGHUP);
}
static double
tvsub(const struct timeval *a, const struct timeval *b)
{
long sdiff;
long udiff;
sdiff = a->tv_sec - b->tv_sec;
udiff = a->tv_usec - b->tv_usec;
return (double)(sdiff * 1000000 + udiff) / 1e6;
}
int fifo(int argc, char *argv[])
{
int e = 0;
volatile long *p, pid;
int i;
struct sched_param fifo_param;
struct timespec interval;
#define MAX_RANAT 32
struct timeval ranat[MAX_RANAT];
#ifdef CAN_USE_ALARMS
static struct itimerval itimerval;
#endif
/* What is the round robin interval?
*/
if (sched_rr_get_interval(0, &interval) == -1) {
perror("sched_rr_get_interval");
exit(errno);
}
#ifdef CAN_USE_ALARMS
signal(SIGALRM, tick);
#endif
fifo_param.sched_priority = 1;
p = (long *)mmap(0, sizeof(*p),
PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, -1, 0);
if (p == (long *)-1)
err(errno, "mmap");
*p = 0;
if (sched_setscheduler(0, SCHED_FIFO, &fifo_param) == -1)
{
perror("sched_setscheduler");
return -1;
}
pid = getpid();
if ((child = fork()) == 0)
{
/* Child process. Just keep setting the pointer to our
* PID. The parent will kill us when it wants to.
*/
pid = getpid();
while (1)
*p = pid;
}
else
{
atexit(tidyup);
*p = pid;
ticked = 0;
#ifdef CAN_USE_ALARMS
/* Set an alarm for 250 times the round-robin interval.
* Then we will verify that a similar priority process
* will not run when we are using the FIFO scheduler.
*/
itimerval.it_value.tv_usec = interval.tv_nsec / (1000 / 250);
itimerval.it_value.tv_sec = itimerval.it_value.tv_usec / 1000000;
itimerval.it_value.tv_usec %= 1000000;
if (setitimer(ITIMER_REAL, &itimerval, 0) == -1) {
perror("setitimer");
exit(errno);
}
#endif
gettimeofday(ranat, 0);
i = 1;
while (!ticked && i < MAX_RANAT)
if (*p == child) {
gettimeofday(ranat + i, 0);
*p = 0;
e = -1;
i++;
}
if (e) {
int j;
fprintf(stderr,
"SCHED_FIFO had erroneous context switches:\n");
for (j = 1; j < i; j++) {
fprintf(stderr, "%d %g\n", j,
tvsub(ranat + j, ranat + j - 1));
}
return e;
}
/* Switch to the round robin scheduler and the child
* should run within twice the interval.
*/
if (sched_setscheduler(child, SCHED_RR, &fifo_param) == -1 ||
sched_setscheduler(0, SCHED_RR, &fifo_param) == -1)
{
perror("sched_setscheduler");
return -1;
}
e = -1;
ticked = 0;
#ifdef CAN_USE_ALARMS
/* Now we do want to see it run. But only set
* the alarm for twice the interval:
*/
itimerval.it_value.tv_usec = interval.tv_nsec / 500;
if (setitimer(ITIMER_REAL, &itimerval, 0) == -1) {
perror("setitimer");
exit(errno);
}
#endif
for (i = 0; !ticked; i++)
if (*p == child) {
e = 0;
break;
}
if (e)
fprintf(stderr,"Child never ran when it should have.\n");
}
exit(e);
}
#ifdef STANDALONE_TESTS
int main(int argc, char *argv[]) { return fifo(argc, argv); }
#endif
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