lib/libthr/thread/thr_spinlock.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1997 John Birrell <jb@cimlogic.com.au>.
   5  * 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. Neither the name of the author nor the names of any co-contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 __FBSDID("$FreeBSD$");
  34
  35 #include <sys/types.h>
  36 #include <pthread.h>
  37 #include <libc_private.h>
  38 #include <spinlock.h>
  39
  40 #include "thr_private.h"
  41
  42 #define MAX_SPINLOCKS   72
  43
  44 /*
  45  * These data structures are used to trace all spinlocks
  46  * in libc.
  47  */
  48 struct spinlock_extra {
  49         spinlock_t      *owner;
  50         struct umutex   lock;
  51 };
  52
  53 static struct umutex            spinlock_static_lock = DEFAULT_UMUTEX;
  54 static struct spinlock_extra    extra[MAX_SPINLOCKS];
  55 static int                      spinlock_count;
  56 static int                      initialized;
  57
  58 static void     init_spinlock(spinlock_t *lck);
  59
  60 /*
  61  * These are for compatibility only.  Spinlocks of this type
  62  * are deprecated.
  63  */
  64
  65 void
  66 __thr_spinunlock(spinlock_t *lck)
  67 {
  68         struct spinlock_extra   *_extra;
  69
  70         _extra = lck->thr_extra;
  71         THR_UMUTEX_UNLOCK(_get_curthread(), &_extra->lock);
  72 }
  73
  74 void
  75 __thr_spinlock(spinlock_t *lck)
  76 {
  77         struct spinlock_extra *_extra;
  78
  79         if (!_thr_isthreaded())
  80                 PANIC("Spinlock called when not threaded.");
  81         if (!initialized)
  82                 PANIC("Spinlocks not initialized.");
  83         if (lck->thr_extra == NULL)
  84                 init_spinlock(lck);
  85         _extra = lck->thr_extra;
  86         THR_UMUTEX_LOCK(_get_curthread(), &_extra->lock);
  87 }
  88
  89 static void
  90 init_spinlock(spinlock_t *lck)
  91 {
  92         struct pthread *curthread = _get_curthread();
  93
  94         THR_UMUTEX_LOCK(curthread, &spinlock_static_lock);
  95         if ((lck->thr_extra == NULL) && (spinlock_count < MAX_SPINLOCKS)) {
  96                 lck->thr_extra = &extra[spinlock_count];
  97                 _thr_umutex_init(&extra[spinlock_count].lock);
  98                 extra[spinlock_count].owner = lck;
  99                 spinlock_count++;
 100         }
 101         THR_UMUTEX_UNLOCK(curthread, &spinlock_static_lock);
 102         if (lck->thr_extra == NULL)
 103                 PANIC("Warning: exceeded max spinlocks");
 104 }
 105
 106 void
 107 _thr_spinlock_init(void)
 108 {
 109         int i;
 110
 111         _thr_umutex_init(&spinlock_static_lock);
 112         if (initialized != 0) {
 113                 /*
 114                  * called after fork() to reset state of libc spin locks,
 115                  * it is not quite right since libc may be in inconsistent
 116                  * state, resetting the locks to allow current thread to be
 117                  * able to hold them may not help things too much, but
 118                  * anyway, we do our best.
 119                  * it is better to do pthread_atfork in libc.
 120                  */
 121                 for (i = 0; i < spinlock_count; i++)
 122                         _thr_umutex_init(&extra[i].lock);
 123         } else {
 124                 initialized = 1;
 125         }
 126 }