tools/regression/p1003_1b/fifo.c

   1 /*
   2  * Copyright (c) 1996 - 2000
   3  *      HD Associates, Inc.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by HD Associates, Inc
  16  * 4. Neither the name of the author nor the names of any co-contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY HD ASSOCIATES AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL HD ASSOCIATES OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * $FreeBSD: src/tools/regression/p1003_1b/fifo.c,v 1.1 2000/02/16 14:28:40 dufault Exp $
  33  * $DragonFly: src/tools/regression/p1003_1b/fifo.c,v 1.3 2007/06/26 23:30:05 josepht Exp $
  34  */
  35 #include <unistd.h>
  36 #include <stdlib.h>
  37 #include <stdio.h>
  38 #include <errno.h>
  39 #include <err.h>
  40 #include <fcntl.h>
  41 #include <sys/types.h>
  42 #include <sys/mman.h>
  43 #include <sys/time.h>
  44 #include <sys/sched.h>
  45 #include <signal.h>
  46
  47 volatile int ticked;
  48 #define CAN_USE_ALARMS
  49
  50 #ifdef CAN_USE_ALARMS
  51 void tick(int arg)
  52 {
  53         ticked = 1;
  54 }
  55 #endif
  56
  57 /* Fifo: Verify that fifo and round-robin scheduling seem to work.
  58  *
  59  * This tests:
  60  * 1. That sched_rr_get_interval seems to work;
  61  * 2. That FIFO scheduling doesn't seeem to be round-robin;
  62  * 3. That round-robin scheduling seems to work.
  63  *
  64  */
  65 static pid_t child;
  66 static void tidyup(void)
  67 {
  68         if (child)
  69                 kill(child, SIGHUP);
  70 }
  71
  72 static double
  73 tvsub(const struct timeval *a, const struct timeval *b)
  74 {
  75         long sdiff;
  76         long udiff;
  77
  78         sdiff = a->tv_sec - b->tv_sec;
  79         udiff = a->tv_usec - b->tv_usec;
  80
  81         return (double)(sdiff * 1000000 + udiff) / 1e6;
  82 }
  83
  84 int fifo(int argc, char *argv[])
  85 {
  86         int e = 0;
  87         volatile long *p, pid;
  88         int i;
  89         struct sched_param fifo_param;
  90         struct timespec interval;
  91 #define MAX_RANAT 32
  92         struct timeval ranat[MAX_RANAT];
  93
  94 #ifdef CAN_USE_ALARMS
  95         static struct itimerval itimerval;
  96 #endif
  97
  98         /* What is the round robin interval?
  99          */
 100
 101         if (sched_rr_get_interval(0, &interval) == -1) {
 102                 perror("sched_rr_get_interval");
 103                 exit(errno);
 104         }
 105
 106 #ifdef CAN_USE_ALARMS
 107         signal(SIGALRM, tick);
 108 #endif
 109
 110         fifo_param.sched_priority = 1;
 111
 112         p = (long *)mmap(0, sizeof(*p),
 113         PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED|MAP_INHERIT, -1, 0);
 114
 115         if (p == (long *)-1)
 116                 err(errno, "mmap");
 117
 118         *p = 0;
 119
 120         if (sched_setscheduler(0, SCHED_FIFO, &fifo_param) == -1)
 121         {
 122                 perror("sched_setscheduler");
 123                 return -1;
 124         }
 125
 126         pid = getpid();
 127
 128         if ((child = fork()) == 0)
 129         {
 130                 /* Child process.  Just keep setting the pointer to our
 131                  * PID.  The parent will kill us when it wants to.
 132                  */
 133
 134                 pid = getpid();
 135                 while (1)
 136                         *p = pid;
 137         }
 138         else
 139         {
 140                 atexit(tidyup);
 141                 *p = pid;
 142
 143
 144                 ticked = 0;
 145
 146 #ifdef CAN_USE_ALARMS
 147                 /* Set an alarm for 250 times the round-robin interval.
 148                  * Then we will verify that a similar priority process
 149                  * will not run when we are using the FIFO scheduler.
 150                  */
 151                 itimerval.it_value.tv_usec = interval.tv_nsec / (1000 / 250);
 152
 153                 itimerval.it_value.tv_sec = itimerval.it_value.tv_usec / 1000000;
 154                 itimerval.it_value.tv_usec %= 1000000;
 155
 156
 157                 if (setitimer(ITIMER_REAL, &itimerval, 0) == -1) {
 158                         perror("setitimer");
 159                         exit(errno);
 160                 }
 161 #endif
 162
 163
 164                 gettimeofday(ranat, 0);
 165                 i = 1;
 166                 while (!ticked && i < MAX_RANAT)
 167                         if (*p == child) {
 168                                 gettimeofday(ranat + i, 0);
 169                                 *p = 0;
 170                                 e = -1;
 171                                 i++;
 172                         }
 173
 174                 if (e) {
 175                         int j;
 176
 177                         fprintf(stderr,
 178                         "SCHED_FIFO had erroneous context switches:\n");
 179                         for (j = 1; j < i; j++) {
 180                                 fprintf(stderr, "%d %g\n", j,
 181                                         tvsub(ranat + j, ranat + j - 1));
 182                         }
 183                         return e;
 184                 }
 185
 186                 /* Switch to the round robin scheduler and the child
 187                  * should run within twice the interval.
 188                  */
 189                 if (sched_setscheduler(child, SCHED_RR, &fifo_param) == -1 ||
 190                 sched_setscheduler(0, SCHED_RR, &fifo_param) == -1)
 191                 {
 192                         perror("sched_setscheduler");
 193                         return -1;
 194                 }
 195
 196                 e = -1;
 197
 198                 ticked = 0;
 199
 200 #ifdef CAN_USE_ALARMS
 201
 202                 /* Now we do want to see it run.  But only set
 203                  * the alarm for twice the interval:
 204                  */
 205                 itimerval.it_value.tv_usec = interval.tv_nsec / 500;
 206
 207                 if (setitimer(ITIMER_REAL, &itimerval, 0) == -1) {
 208                         perror("setitimer");
 209                         exit(errno);
 210                 }
 211 #endif
 212
 213                 for (i = 0; !ticked; i++)
 214                         if (*p == child) {
 215                                 e = 0;
 216                                 break;
 217                         }
 218
 219                 if (e)
 220                         fprintf(stderr,"Child never ran when it should have.\n");
 221         }
 222
 223         exit(e);
 224 }
 225
 226 #ifdef STANDALONE_TESTS
 227 int main(int argc, char *argv[]) { return fifo(argc, argv); }
 228 #endif