6/lib/libpthread/thread/thr_concurrency.c

   1 /*
   2  * Copyright (c) 2003 Daniel M. Eischen <deischen@freebsd.org>
   3  * Copyright (c) 2003 Sergey Osokin <osa@freebsd.org.ru>.
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Neither the name of the author nor the names of any co-contributors
  12  *    may be used to endorse or promote products derived from this software
  13  *    without specific prior written permission.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
  16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  25  * SUCH DAMAGE.
  26  *
  27  * $FreeBSD$
  28  */
  29 #include <errno.h>
  30 #include <pthread.h>
  31 #include <sys/types.h>
  32 #include <sys/sysctl.h>
  33
  34 #include "thr_private.h"
  35
  36 /*#define DEBUG_CONCURRENCY */
  37 #ifdef DEBUG_CONCURRENCY
  38 #define DBG_MSG         stdout_debug
  39 #else
  40 #define DBG_MSG(x...)
  41 #endif
  42
  43 static int level = 0;
  44
  45 __weak_reference(_pthread_getconcurrency, pthread_getconcurrency);
  46 __weak_reference(_pthread_setconcurrency, pthread_setconcurrency);
  47
  48 int
  49 _pthread_getconcurrency(void)
  50 {
  51         return (level);
  52 }
  53
  54 int
  55 _pthread_setconcurrency(int new_level)
  56 {
  57         int ret;
  58
  59         if (new_level < 0)
  60                 ret = EINVAL;
  61         else if (new_level == level)
  62                 ret = 0;
  63         else if (new_level == 0) {
  64                 level = 0;
  65                 ret = 0;
  66         } else if ((_kse_isthreaded() == 0) && (_kse_setthreaded(1) != 0)) {
  67                 DBG_MSG("Can't enable threading.\n");
  68                 ret = EAGAIN;
  69         } else {
  70                 ret = _thr_setconcurrency(new_level);
  71                 if (ret == 0)
  72                         level = new_level;
  73         }
  74         return (ret);
  75 }
  76
  77 int
  78 _thr_setconcurrency(int new_level)
  79 {
  80         struct pthread *curthread;
  81         struct kse *newkse, *kse;
  82         kse_critical_t crit;
  83         int kse_count;
  84         int i;
  85         int ret;
  86
  87         /*
  88          * Turn on threaded mode, if failed, it is unnecessary to
  89          * do further work.
  90          */
  91         if (_kse_isthreaded() == 0 && _kse_setthreaded(1))
  92                 return (EAGAIN);
  93
  94         ret = 0;
  95         curthread = _get_curthread();
  96         /* Race condition, but so what. */
  97         kse_count = _kse_initial->k_kseg->kg_ksecount;
  98         if (new_level > kse_count) {
  99                 for (i = kse_count; i < new_level; i++) {
 100                         newkse = _kse_alloc(curthread, 0);
 101                         if (newkse == NULL) {
 102                                 DBG_MSG("Can't alloc new KSE.\n");
 103                                 ret = EAGAIN;
 104                                 break;
 105                         }
 106                         newkse->k_kseg = _kse_initial->k_kseg;
 107                         newkse->k_schedq = _kse_initial->k_schedq;
 108                         newkse->k_curthread = NULL;
 109                         crit = _kse_critical_enter();
 110                         KSE_SCHED_LOCK(curthread->kse, newkse->k_kseg);
 111                         TAILQ_INSERT_TAIL(&newkse->k_kseg->kg_kseq,
 112                             newkse, k_kgqe);
 113                         newkse->k_kseg->kg_ksecount++;
 114                         newkse->k_flags |= KF_STARTED;
 115                         KSE_SCHED_UNLOCK(curthread->kse, newkse->k_kseg);
 116                         if (kse_create(&newkse->k_kcb->kcb_kmbx, 0) != 0) {
 117                                 KSE_SCHED_LOCK(curthread->kse, newkse->k_kseg);
 118                                 TAILQ_REMOVE(&newkse->k_kseg->kg_kseq,
 119                                     newkse, k_kgqe);
 120                                 newkse->k_kseg->kg_ksecount--;
 121                                 KSE_SCHED_UNLOCK(curthread->kse,
 122                                     newkse->k_kseg);
 123                                 _kse_critical_leave(crit);
 124                                 _kse_free(curthread, newkse);
 125                                 DBG_MSG("kse_create syscall failed.\n");
 126                                 ret = EAGAIN;
 127                                 break;
 128                         } else {
 129                                 _kse_critical_leave(crit);
 130                         }
 131                 }
 132         } else if (new_level < kse_count) {
 133                 kse_count = 0;
 134                 crit = _kse_critical_enter();
 135                 KSE_SCHED_LOCK(curthread->kse, _kse_initial->k_kseg);
 136                 /* Count the number of active KSEs */
 137                 TAILQ_FOREACH(kse, &_kse_initial->k_kseg->kg_kseq, k_kgqe) {
 138                         if ((kse->k_flags & KF_TERMINATED) == 0)
 139                                 kse_count++;
 140                 }
 141                 /* Reduce the number of active KSEs appropriately. */
 142                 kse = TAILQ_FIRST(&_kse_initial->k_kseg->kg_kseq);
 143                 while ((kse != NULL) && (kse_count > new_level)) {
 144                         if ((kse != _kse_initial) &&
 145                             ((kse->k_flags & KF_TERMINATED) == 0)) {
 146                                 kse->k_flags |= KF_TERMINATED;
 147                                 kse_count--;
 148                                 /* Wakup the KSE in case it is idle. */
 149                                 kse_wakeup(&kse->k_kcb->kcb_kmbx);
 150                         }
 151                         kse = TAILQ_NEXT(kse, k_kgqe);
 152                 }
 153                 KSE_SCHED_UNLOCK(curthread->kse, _kse_initial->k_kseg);
 154                 _kse_critical_leave(crit);
 155         }
 156         return (ret);
 157 }
 158
 159 int
 160 _thr_setmaxconcurrency(void)
 161 {
 162         int vcpu;
 163         size_t len;
 164         int ret;
 165
 166         len = sizeof(vcpu);
 167         ret = sysctlbyname("kern.threads.virtual_cpu", &vcpu, &len, NULL, 0);
 168         if (ret == 0 && vcpu > 0)
 169                 ret = _thr_setconcurrency(vcpu);
 170         return (ret);
 171 }
 172