thr_spinlock.c revision 123314 
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. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by John Birrell.
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 JOHN BIRRELL 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 THE AUTHOR 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 * $FreeBSD: head/lib/libkse/thread/thr_spinlock.c 123314 2003-12-09 02:37:40Z davidxu $
33 *
34 */
35
36#include <sys/types.h>
37#include <machine/atomic.h>
38
39#include <libc_private.h>
40#include "spinlock.h"
41#include "thr_private.h"
42
43#define	MAX_SPINLOCKS	5
44
45struct spinlock_extra {
46	spinlock_t	*owner;
47	pthread_mutex_t	lock;
48};
49
50static void	init_spinlock(spinlock_t *lck);
51
52static pthread_mutex_t		spinlock_static_lock;
53static struct spinlock_extra	extra[MAX_SPINLOCKS];
54static int			spinlock_count = 0;
55static int			initialized = 0;
56
57/*
58 * These are for compatability only.  Spinlocks of this type
59 * are deprecated.
60 */
61
62void
63_spinunlock(spinlock_t *lck)
64{
65	struct spinlock_extra *extra;
66
67	extra = (struct spinlock_extra *)lck->fname;
68	pthread_mutex_unlock(&extra->lock);
69}
70
71/*
72 * Lock a location for the running thread. Yield to allow other
73 * threads to run if this thread is blocked because the lock is
74 * not available. Note that this function does not sleep. It
75 * assumes that the lock will be available very soon.
76 */
77void
78_spinlock(spinlock_t *lck)
79{
80	struct spinlock_extra *extra;
81
82	if (!__isthreaded)
83		PANIC("Spinlock called when not threaded.");
84	if (!initialized)
85		PANIC("Spinlocks not initialized.");
86	/*
87	 * Try to grab the lock and loop if another thread grabs
88	 * it before we do.
89	 */
90	if (lck->fname == NULL)
91		init_spinlock(lck);
92	extra = (struct spinlock_extra *)lck->fname;
93	pthread_mutex_lock(&extra->lock);
94}
95
96/*
97 * Lock a location for the running thread. Yield to allow other
98 * threads to run if this thread is blocked because the lock is
99 * not available. Note that this function does not sleep. It
100 * assumes that the lock will be available very soon.
101 *
102 * This function checks if the running thread has already locked the
103 * location, warns if this occurs and creates a thread dump before
104 * returning.
105 */
106void
107_spinlock_debug(spinlock_t *lck, char *fname, int lineno)
108{
109	_spinlock(lck);
110}
111
112static void
113init_spinlock(spinlock_t *lck)
114{
115	pthread_mutex_lock(&spinlock_static_lock);
116	if ((lck->fname == NULL) && (spinlock_count < MAX_SPINLOCKS)) {
117		lck->fname = (char *)&extra[spinlock_count];
118		extra[spinlock_count].owner = lck;
119		spinlock_count++;
120	}
121	pthread_mutex_unlock(&spinlock_static_lock);
122	if (lck->fname == NULL)
123		PANIC("Exceeded max spinlocks");
124}
125
126void
127_thr_spinlock_init(void)
128{
129	int i;
130
131	if (initialized != 0) {
132		_thr_mutex_reinit(&spinlock_static_lock);
133		for (i = 0; i < spinlock_count; i++)
134			_thr_mutex_reinit(&extra[i].lock);
135	} else {
136		if (pthread_mutex_init(&spinlock_static_lock, NULL))
137			PANIC("Cannot initialize spinlock_static_lock");
138		for (i = 0; i < MAX_SPINLOCKS; i++) {
139			if (pthread_mutex_init(&extra[i].lock, NULL))
140				PANIC("Cannot initialize spinlock extra");
141		}
142		initialized = 1;
143	}
144}
145