sx.h revision 73901 
1/*
2 * Copyright (C) 2001 Jason Evans <jasone@freebsd.org>.  All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice(s), this list of conditions and the following disclaimer as
9 *    the first lines of this file unmodified other than the possible
10 *    addition of one or more copyright notices.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice(s), this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
16 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
17 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
18 * DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
19 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
20 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
21 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
22 * 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 SUCH
25 * DAMAGE.
26 *
27 * $FreeBSD: head/sys/sys/sx.h 73901 2001-03-06 23:13:15Z jhb $
28 */
29
30#ifndef	_SYS_SX_H_
31#define	_SYS_SX_H_
32
33#ifndef	LOCORE
34#include <sys/mutex.h>
35#include <sys/condvar.h>
36
37struct sx {
38	struct mtx	sx_lock;	/* General protection lock. */
39	const char	*sx_descr;	/* sx lock description. */
40	int		sx_cnt;		/* -1: xlock, > 0: slock count. */
41	struct cv	sx_shrd_cv;	/* slock waiters. */
42	int		sx_shrd_wcnt;	/* Number of slock waiters. */
43	struct cv	sx_excl_cv;	/* xlock waiters. */
44	int		sx_excl_wcnt;	/* Number of xlock waiters. */
45	struct proc	*sx_xholder;	/* Thread presently holding xlock. */
46};
47
48#ifdef _KERNEL
49void	sx_init(struct sx *sx, const char *description);
50void	sx_destroy(struct sx *sx);
51void	sx_slock(struct sx *sx);
52void	sx_xlock(struct sx *sx);
53void	sx_sunlock(struct sx *sx);
54void	sx_xunlock(struct sx *sx);
55
56#ifdef INVARIANTS
57/*
58 * SX_ASSERT_SLOCKED() can only detect that at least *some* thread owns an
59 * slock, but it cannot guarantee that *this* thread owns an slock.
60 */
61#define	SX_ASSERT_SLOCKED(sx) do {					\
62	mtx_lock(&(sx)->sx_lock);					\
63	_SX_ASSERT_SLOCKED((sx));					\
64	mtx_unlock(&(sx)->sx_lock);					\
65} while (0)
66#define	_SX_ASSERT_SLOCKED(sx) do {					\
67	KASSERT(((sx)->sx_cnt > 0), ("%s: lacking slock %s\n",		\
68	    __FUNCTION__, (sx)->sx_descr));				\
69} while (0)
70
71/*
72 * SX_ASSERT_XLOCKED() detects and guarantees that *we* own the xlock.
73 */
74#define	SX_ASSERT_XLOCKED(sx) do {					\
75	mtx_lock(&(sx)->sx_lock);					\
76	_SX_ASSERT_XLOCKED((sx));					\
77	mtx_unlock(&(sx)->sx_lock);					\
78} while (0)
79#define	_SX_ASSERT_XLOCKED(sx) do {					\
80	KASSERT(((sx)->sx_xholder == curproc),				\
81	    ("%s: thread %p lacking xlock %s\n", __FUNCTION__,		\
82	    curproc, (sx)->sx_descr));					\
83} while (0)
84
85#else	/* INVARIANTS */
86#define	SX_ASSERT_SLOCKED(sx)
87#define	SX_ASSERT_XLOCKED(sx)
88#define	_SX_ASSERT_SLOCKED(sx)
89#define	_SX_ASSERT_XLOCKED(sx)
90#endif	/* INVARIANTS */
91
92#endif	/* _KERNEL */
93#endif	/* !LOCORE */
94#endif	/* _SYS_SX_H_ */
95