thr_spinlock.c revision 331722 
1/*
2 * Copyright (c) 1997 John Birrell <jb@cimlogic.com.au>.
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 * 3. Neither the name of the author nor the names of any co-contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#include <sys/cdefs.h>
31__FBSDID("$FreeBSD: stable/11/lib/libthr/thread/thr_spinlock.c 331722 2018-03-29 02:50:57Z eadler $");
32
33#include <sys/types.h>
34#include <pthread.h>
35#include <libc_private.h>
36#include <spinlock.h>
37
38#include "thr_private.h"
39
40#define	MAX_SPINLOCKS	72
41
42/*
43 * These data structures are used to trace all spinlocks
44 * in libc.
45 */
46struct spinlock_extra {
47	spinlock_t	*owner;
48	struct umutex	lock;
49};
50
51static struct umutex		spinlock_static_lock = DEFAULT_UMUTEX;
52static struct spinlock_extra	extra[MAX_SPINLOCKS];
53static int			spinlock_count;
54static int			initialized;
55
56static void	init_spinlock(spinlock_t *lck);
57
58/*
59 * These are for compatability only.  Spinlocks of this type
60 * are deprecated.
61 */
62
63void
64__thr_spinunlock(spinlock_t *lck)
65{
66	struct spinlock_extra	*_extra;
67
68	_extra = lck->thr_extra;
69	THR_UMUTEX_UNLOCK(_get_curthread(), &_extra->lock);
70}
71
72void
73__thr_spinlock(spinlock_t *lck)
74{
75	struct spinlock_extra *_extra;
76
77	if (!__isthreaded)
78		PANIC("Spinlock called when not threaded.");
79	if (!initialized)
80		PANIC("Spinlocks not initialized.");
81	if (lck->thr_extra == NULL)
82		init_spinlock(lck);
83	_extra = lck->thr_extra;
84	THR_UMUTEX_LOCK(_get_curthread(), &_extra->lock);
85}
86
87static void
88init_spinlock(spinlock_t *lck)
89{
90	struct pthread *curthread = _get_curthread();
91
92	THR_UMUTEX_LOCK(curthread, &spinlock_static_lock);
93	if ((lck->thr_extra == NULL) && (spinlock_count < MAX_SPINLOCKS)) {
94		lck->thr_extra = &extra[spinlock_count];
95		_thr_umutex_init(&extra[spinlock_count].lock);
96		extra[spinlock_count].owner = lck;
97		spinlock_count++;
98	}
99	THR_UMUTEX_UNLOCK(curthread, &spinlock_static_lock);
100	if (lck->thr_extra == NULL)
101		PANIC("Warning: exceeded max spinlocks");
102}
103
104void
105_thr_spinlock_init(void)
106{
107	int i;
108
109	_thr_umutex_init(&spinlock_static_lock);
110	if (initialized != 0) {
111		/*
112		 * called after fork() to reset state of libc spin locks,
113		 * it is not quite right since libc may be in inconsistent
114		 * state, resetting the locks to allow current thread to be
115		 * able to hold them may not help things too much, but
116		 * anyway, we do our best.
117		 * it is better to do pthread_atfork in libc.
118		 */
119		for (i = 0; i < spinlock_count; i++)
120			_thr_umutex_init(&extra[i].lock);
121	} else {
122		initialized = 1;
123	}
124}
125