lib/libkse/thread/thr_pspinlock.c

   1 /*-
   2  * Copyright (c) 2003 David Xu <davidxu@freebsd.org>
   3  * 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  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  *
  26  * $FreeBSD$
  27  */
  28
  29 #include <errno.h>
  30 #include <stdlib.h>
  31 #include <pthread.h>
  32 #include <atomic_ops.h>
  33 #include "thr_private.h"
  34
  35 #define SPIN_COUNT 10000
  36
  37 __weak_reference(_pthread_spin_init, pthread_spin_init);
  38 __weak_reference(_pthread_spin_destroy, pthread_spin_destroy);
  39 __weak_reference(_pthread_spin_trylock, pthread_spin_trylock);
  40 __weak_reference(_pthread_spin_lock, pthread_spin_lock);
  41 __weak_reference(_pthread_spin_unlock, pthread_spin_unlock);
  42
  43 int
  44 _pthread_spin_init(pthread_spinlock_t *lock, int pshared)
  45 {
  46         struct pthread_spinlock *lck;
  47         int ret;
  48
  49         if (lock == NULL || pshared != PTHREAD_PROCESS_PRIVATE)
  50                 ret = EINVAL;
  51         else if ((lck = malloc(sizeof(struct pthread_spinlock))) == NULL)
  52                 ret = ENOMEM;
  53         else {
  54                 lck->s_lock = 0;
  55                 lck->s_owner= NULL;
  56                 *lock = lck;
  57                 ret = 0;
  58         }
  59
  60         return (ret);
  61 }
  62
  63 int
  64 _pthread_spin_destroy(pthread_spinlock_t *lock)
  65 {
  66         int ret;
  67
  68         if (lock == NULL || *lock == NULL)
  69                 ret = EINVAL;
  70         else if ((*lock)->s_owner != NULL)
  71                 ret = EBUSY;
  72         else {
  73                 free(*lock);
  74                 *lock = NULL;
  75                 ret = 0;
  76         }
  77
  78         return (ret);
  79 }
  80
  81 int
  82 _pthread_spin_trylock(pthread_spinlock_t *lock)
  83 {
  84         struct pthread_spinlock *lck;
  85         struct pthread *self = _pthread_self();
  86         int oldval, ret;
  87
  88         if (lock == NULL || (lck = *lock) == NULL)
  89                 ret = EINVAL;
  90         else if (lck->s_owner == self)
  91                 ret = EDEADLK;
  92         else if (lck->s_lock != 0)
  93                 ret = EBUSY;
  94         else {
  95                 atomic_swap_int((int *)&(lck)->s_lock, 1, &oldval);
  96                 if (oldval)
  97                         ret = EBUSY;
  98                 else {
  99                         lck->s_owner = _pthread_self();
 100                         ret = 0;
 101                 }
 102         }
 103         return (ret);
 104 }
 105
 106 int
 107 _pthread_spin_lock(pthread_spinlock_t *lock)
 108 {
 109         struct pthread_spinlock *lck;
 110         struct pthread *self = _pthread_self();
 111         int count, oldval, ret;
 112
 113         if (lock == NULL || (lck = *lock) == NULL)
 114                 ret = EINVAL;
 115         else if (lck->s_owner == self)
 116                 ret = EDEADLK;
 117         else {
 118                 do {
 119                         count = SPIN_COUNT;
 120                         while (lck->s_lock) {
 121 #ifdef __i386__
 122                                 /* tell cpu we are spinning */
 123                                 __asm __volatile("pause");
 124 #endif
 125                                 if (--count <= 0) {
 126                                         count = SPIN_COUNT;
 127                                         _pthread_yield();
 128                                 }
 129                         }
 130                         atomic_swap_int((int *)&(lck)->s_lock, 1, &oldval);
 131                 } while (oldval);
 132
 133                 lck->s_owner = self;
 134                 ret = 0;
 135         }
 136
 137         return (ret);
 138 }
 139
 140 int
 141 _pthread_spin_unlock(pthread_spinlock_t *lock)
 142 {
 143         struct pthread_spinlock *lck;
 144         int ret;
 145
 146         if (lock == NULL || (lck = *lock) == NULL)
 147                 ret = EINVAL;
 148         else {
 149                 if (lck->s_owner != _pthread_self())
 150                         ret = EPERM;
 151                 else {
 152                         lck->s_owner = NULL;
 153                         atomic_swap_int((int *)&lck->s_lock, 0, &ret);
 154                         ret = 0;
 155                 }
 156         }
 157
 158         return (ret);
 159 }
 160