The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/ksched.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-4-Clause
    3  *
    4  * Copyright (c) 1996, 1997
    5  *      HD Associates, Inc.  All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. All advertising materials mentioning features or use of this software
   16  *    must display the following acknowledgement:
   17  *      This product includes software developed by HD Associates, Inc
   18  * 4. Neither the name of the author nor the names of any co-contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY HD ASSOCIATES AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL HD ASSOCIATES OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  */
   34 
   35 /* ksched: Soft real time scheduling based on "rtprio". */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD$");
   39 
   40 #include "opt_posix.h"
   41 
   42 #include <sys/param.h>
   43 #include <sys/systm.h>
   44 #include <sys/lock.h>
   45 #include <sys/sysctl.h>
   46 #include <sys/kernel.h>
   47 #include <sys/mutex.h>
   48 #include <sys/proc.h>
   49 #include <sys/posix4.h>
   50 #include <sys/resource.h>
   51 #include <sys/sched.h>
   52 
   53 FEATURE(kposix_priority_scheduling, "POSIX P1003.1B realtime extensions");
   54 
   55 /* ksched: Real-time extension to support POSIX priority scheduling. */
   56 
   57 struct ksched {
   58         struct timespec rr_interval;
   59 };
   60 
   61 int
   62 ksched_attach(struct ksched **p)
   63 {
   64         struct ksched *ksched;
   65 
   66         ksched = malloc(sizeof(*ksched), M_P31B, M_WAITOK);
   67         ksched->rr_interval.tv_sec = 0;
   68         ksched->rr_interval.tv_nsec = 1000000000L / hz * sched_rr_interval();
   69         *p = ksched;
   70         return (0);
   71 }
   72 
   73 int
   74 ksched_detach(struct ksched *ks)
   75 {
   76 
   77         free(ks, M_P31B);
   78         return (0);
   79 }
   80 
   81 /*
   82  * XXX About priorities
   83  *
   84  *      POSIX 1003.1b requires that numerically higher priorities be of
   85  *      higher priority.  It also permits sched_setparam to be
   86  *      implementation defined for SCHED_OTHER.  I don't like
   87  *      the notion of inverted priorites for normal processes when
   88  *      you can use "setpriority" for that.
   89  *
   90  */
   91 
   92 /* Macros to convert between the unix (lower numerically is higher priority)
   93  * and POSIX 1003.1b (higher numerically is higher priority)
   94  */
   95 
   96 #define p4prio_to_rtpprio(P) (RTP_PRIO_MAX - (P))
   97 #define rtpprio_to_p4prio(P) (RTP_PRIO_MAX - (P))
   98 
   99 #define p4prio_to_tsprio(P) ((PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE) - (P))
  100 #define tsprio_to_p4prio(P) ((PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE) - (P))
  101 
  102 /* These improve readability a bit for me:
  103  */
  104 #define P1B_PRIO_MIN rtpprio_to_p4prio(RTP_PRIO_MAX)
  105 #define P1B_PRIO_MAX rtpprio_to_p4prio(RTP_PRIO_MIN)
  106 
  107 static __inline int
  108 getscheduler(struct ksched *ksched, struct thread *td, int *policy)
  109 {
  110         struct rtprio rtp;
  111         int e;
  112 
  113         e = 0;
  114         pri_to_rtp(td, &rtp);
  115         switch (rtp.type) {
  116         case RTP_PRIO_FIFO:
  117                 *policy = SCHED_FIFO;
  118                 break;
  119         case RTP_PRIO_REALTIME:
  120                 *policy = SCHED_RR;
  121                 break;
  122         default:
  123                 *policy = SCHED_OTHER;
  124                 break;
  125         }
  126         return (e);
  127 }
  128 
  129 int
  130 ksched_setparam(struct ksched *ksched,
  131     struct thread *td, const struct sched_param *param)
  132 {
  133         int e, policy;
  134 
  135         e = getscheduler(ksched, td, &policy);
  136         if (e == 0)
  137                 e = ksched_setscheduler(ksched, td, policy, param);
  138         return (e);
  139 }
  140 
  141 int
  142 ksched_getparam(struct ksched *ksched, struct thread *td,
  143     struct sched_param *param)
  144 {
  145         struct rtprio rtp;
  146 
  147         pri_to_rtp(td, &rtp);
  148         if (RTP_PRIO_IS_REALTIME(rtp.type))
  149                 param->sched_priority = rtpprio_to_p4prio(rtp.prio);
  150         else {
  151                 if (PRI_MIN_TIMESHARE < rtp.prio) 
  152                         /*
  153                          * The interactive score has it to min realtime
  154                          * so we must show max (64 most likely).
  155                          */ 
  156                         param->sched_priority = PRI_MAX_TIMESHARE -
  157                             PRI_MIN_TIMESHARE;
  158                 else
  159                         param->sched_priority = tsprio_to_p4prio(rtp.prio);
  160         }
  161         return (0);
  162 }
  163 
  164 /*
  165  * XXX The priority and scheduler modifications should
  166  *     be moved into published interfaces in kern/kern_sync.
  167  *
  168  * The permissions to modify process p were checked in "p31b_proc()".
  169  *
  170  */
  171 int
  172 ksched_setscheduler(struct ksched *ksched, struct thread *td, int policy,
  173     const struct sched_param *param)
  174 {
  175         struct rtprio rtp;
  176         int e;
  177 
  178         e = 0;
  179         switch(policy) {
  180         case SCHED_RR:
  181         case SCHED_FIFO:
  182                 if (param->sched_priority >= P1B_PRIO_MIN &&
  183                     param->sched_priority <= P1B_PRIO_MAX) {
  184                         rtp.prio = p4prio_to_rtpprio(param->sched_priority);
  185                         rtp.type = (policy == SCHED_FIFO) ? RTP_PRIO_FIFO :
  186                             RTP_PRIO_REALTIME;
  187                         rtp_to_pri(&rtp, td);
  188                 } else {
  189                         e = EPERM;
  190                 }
  191                 break;
  192         case SCHED_OTHER:
  193                 if (param->sched_priority >= 0 && param->sched_priority <=
  194                     (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE)) {
  195                         rtp.type = RTP_PRIO_NORMAL;
  196                         rtp.prio = p4prio_to_tsprio(param->sched_priority);
  197                         rtp_to_pri(&rtp, td);
  198                 } else {
  199                         e = EINVAL;
  200                 }
  201                 break;
  202         default:
  203                 e = EINVAL;
  204                 break;
  205         }
  206         return (e);
  207 }
  208 
  209 int
  210 ksched_getscheduler(struct ksched *ksched, struct thread *td, int *policy)
  211 {
  212 
  213         return (getscheduler(ksched, td, policy));
  214 }
  215 
  216 /* ksched_yield: Yield the CPU. */
  217 int
  218 ksched_yield(struct ksched *ksched)
  219 {
  220 
  221         sched_relinquish(curthread);
  222         return (0);
  223 }
  224 
  225 int
  226 ksched_get_priority_max(struct ksched *ksched, int policy, int *prio)
  227 {
  228         int e;
  229 
  230         e = 0;
  231         switch (policy) {
  232         case SCHED_FIFO:
  233         case SCHED_RR:
  234                 *prio = P1B_PRIO_MAX;
  235                 break;
  236         case SCHED_OTHER:
  237                 *prio = PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE;
  238                 break;
  239         default:
  240                 e = EINVAL;
  241                 break;
  242         }
  243         return (e);
  244 }
  245 
  246 int
  247 ksched_get_priority_min(struct ksched *ksched, int policy, int *prio)
  248 {
  249         int e;
  250 
  251         e = 0;
  252         switch (policy) {
  253         case SCHED_FIFO:
  254         case SCHED_RR:
  255                 *prio = P1B_PRIO_MIN;
  256                 break;
  257         case SCHED_OTHER:
  258                 *prio = 0;
  259                 break;
  260         default:
  261                 e = EINVAL;
  262                 break;
  263         }
  264         return (e);
  265 }
  266 
  267 int
  268 ksched_rr_get_interval(struct ksched *ksched, struct thread *td,
  269     struct timespec *timespec)
  270 {
  271 
  272         *timespec = ksched->rr_interval;
  273         return (0);
  274 }

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