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  * Copyright (c) 1996, 1997
    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 
   33 /* ksched: Soft real time scheduling based on "rtprio".
   34  */
   35 
   36 #include <sys/cdefs.h>
   37 __FBSDID("$FreeBSD: releng/7.4/sys/kern/ksched.c 170307 2007-06-05 00:00:57Z jeff $");
   38 
   39 #include "opt_posix.h"
   40 
   41 #include <sys/param.h>
   42 #include <sys/systm.h>
   43 #include <sys/lock.h>
   44 #include <sys/mutex.h>
   45 #include <sys/proc.h>
   46 #include <sys/posix4.h>
   47 #include <sys/resource.h>
   48 #include <sys/sched.h>
   49 
   50 /* ksched: Real-time extension to support POSIX priority scheduling.
   51  */
   52 
   53 struct ksched {
   54         struct timespec rr_interval;
   55 };
   56 
   57 int
   58 ksched_attach(struct ksched **p)
   59 {
   60         struct ksched *ksched= p31b_malloc(sizeof(*ksched));
   61 
   62         ksched->rr_interval.tv_sec = 0;
   63         ksched->rr_interval.tv_nsec = 1000000000L / sched_rr_interval();
   64 
   65         *p = ksched;
   66         return 0;
   67 }
   68 
   69 int
   70 ksched_detach(struct ksched *ks)
   71 {
   72         p31b_free(ks);
   73 
   74         return 0;
   75 }
   76 
   77 /*
   78  * XXX About priorities
   79  *
   80  *      POSIX 1003.1b requires that numerically higher priorities be of
   81  *      higher priority.  It also permits sched_setparam to be
   82  *      implementation defined for SCHED_OTHER.  I don't like
   83  *      the notion of inverted priorites for normal processes when
   84  *  you can use "setpriority" for that.
   85  *
   86  *      I'm rejecting sched_setparam for SCHED_OTHER with EINVAL.
   87  */
   88 
   89 /* Macros to convert between the unix (lower numerically is higher priority)
   90  * and POSIX 1003.1b (higher numerically is higher priority)
   91  */
   92 
   93 #define p4prio_to_rtpprio(P) (RTP_PRIO_MAX - (P))
   94 #define rtpprio_to_p4prio(P) (RTP_PRIO_MAX - (P))
   95 
   96 /* These improve readability a bit for me:
   97  */
   98 #define P1B_PRIO_MIN rtpprio_to_p4prio(RTP_PRIO_MAX)
   99 #define P1B_PRIO_MAX rtpprio_to_p4prio(RTP_PRIO_MIN)
  100 
  101 static __inline int
  102 getscheduler(struct ksched *ksched, struct thread *td, int *policy)
  103 {
  104         struct rtprio rtp;
  105         int e = 0;
  106 
  107         pri_to_rtp(td, &rtp);
  108         switch (rtp.type)
  109         {
  110                 case RTP_PRIO_FIFO:
  111                 *policy = SCHED_FIFO;
  112                 break;
  113 
  114                 case RTP_PRIO_REALTIME:
  115                 *policy = SCHED_RR;
  116                 break;
  117 
  118                 default:
  119                 *policy = SCHED_OTHER;
  120                 break;
  121         }
  122 
  123         return e;
  124 }
  125 
  126 int
  127 ksched_setparam(struct ksched *ksched,
  128     struct thread *td, const struct sched_param *param)
  129 {
  130         int policy;
  131         int e;
  132 
  133         e = getscheduler(ksched, td, &policy);
  134 
  135         if (e == 0)
  136         {
  137                 if (policy == SCHED_OTHER)
  138                         e = EINVAL;
  139                 else
  140                         e = ksched_setscheduler(ksched, td, policy, param);
  141         }
  142 
  143         return e;
  144 }
  145 
  146 int
  147 ksched_getparam(struct ksched *ksched,
  148     struct thread *td, struct sched_param *param)
  149 {
  150         struct rtprio rtp;
  151 
  152         pri_to_rtp(td, &rtp);
  153         if (RTP_PRIO_IS_REALTIME(rtp.type))
  154                 param->sched_priority = rtpprio_to_p4prio(rtp.prio);
  155 
  156         return 0;
  157 }
  158 
  159 /*
  160  * XXX The priority and scheduler modifications should
  161  *     be moved into published interfaces in kern/kern_sync.
  162  *
  163  * The permissions to modify process p were checked in "p31b_proc()".
  164  *
  165  */
  166 int
  167 ksched_setscheduler(struct ksched *ksched,
  168     struct thread *td, int policy, const struct sched_param *param)
  169 {
  170         int e = 0;
  171         struct rtprio rtp;
  172 
  173         switch(policy)
  174         {
  175                 case SCHED_RR:
  176                 case SCHED_FIFO:
  177 
  178                 if (param->sched_priority >= P1B_PRIO_MIN &&
  179                     param->sched_priority <= P1B_PRIO_MAX)
  180                 {
  181                         rtp.prio = p4prio_to_rtpprio(param->sched_priority);
  182                         rtp.type = (policy == SCHED_FIFO)
  183                                 ? RTP_PRIO_FIFO : RTP_PRIO_REALTIME;
  184 
  185                         rtp_to_pri(&rtp, td);
  186                 }
  187                 else
  188                         e = EPERM;
  189 
  190 
  191                 break;
  192 
  193                 case SCHED_OTHER:
  194                 {
  195                         rtp.type = RTP_PRIO_NORMAL;
  196                         rtp.prio = p4prio_to_rtpprio(param->sched_priority);
  197                         rtp_to_pri(&rtp, td);
  198                 }
  199                 break;
  200                 
  201                 default:
  202                         e = EINVAL;
  203                         break;
  204         }
  205 
  206         return e;
  207 }
  208 
  209 int
  210 ksched_getscheduler(struct ksched *ksched, struct thread *td, int *policy)
  211 {
  212         return getscheduler(ksched, td, policy);
  213 }
  214 
  215 /* ksched_yield: Yield the CPU.
  216  */
  217 int
  218 ksched_yield(struct ksched *ksched)
  219 {
  220         sched_relinquish(curthread);
  221         return 0;
  222 }
  223 
  224 int
  225 ksched_get_priority_max(struct ksched *ksched, int policy, int *prio)
  226 {
  227         int e = 0;
  228 
  229         switch (policy)
  230         {
  231                 case SCHED_FIFO:
  232                 case SCHED_RR:
  233                 *prio = RTP_PRIO_MAX;
  234                 break;
  235 
  236                 case SCHED_OTHER:
  237                 *prio = PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE;
  238                 break;
  239 
  240                 default:
  241                 e = EINVAL;
  242         }
  243 
  244         return e;
  245 }
  246 
  247 int
  248 ksched_get_priority_min(struct ksched *ksched, int policy, int *prio)
  249 {
  250         int e = 0;
  251 
  252         switch (policy)
  253         {
  254                 case SCHED_FIFO:
  255                 case SCHED_RR:
  256                 *prio = P1B_PRIO_MIN;
  257                 break;
  258 
  259                 case SCHED_OTHER:
  260                 *prio = 0;
  261                 break;
  262 
  263                 default:
  264                 e = EINVAL;
  265         }
  266 
  267         return e;
  268 }
  269 
  270 int
  271 ksched_rr_get_interval(struct ksched *ksched,
  272    struct thread *td, struct timespec *timespec)
  273 {
  274         *timespec = ksched->rr_interval;
  275 
  276         return 0;
  277 }

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