1/*	$OpenBSD: mutex.h,v 1.22 2024/05/16 09:30:03 kettenis Exp $	*/
2
3/*
4 * Copyright (c) 2004 Artur Grabowski <art@openbsd.org>
5 *
6 * Permission to use, copy, modify, and distribute this software for any
7 * purpose with or without fee is hereby granted, provided that the above
8 * copyright notice and this permission notice appear in all copies.
9 *
10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17 */
18
19#ifndef _SYS_MUTEX_H_
20#define _SYS_MUTEX_H_
21
22/*
23 * A mutex is:
24 *  - owned by a cpu.
25 *  - non-recursive.
26 *  - spinning.
27 *  - not providing mutual exclusion between processes, only cpus.
28 *  - providing interrupt blocking when necessary.
29 *
30 * Different mutexes can be nested, but not interleaved. This is ok:
31 * "mtx_enter(foo); mtx_enter(bar); mtx_leave(bar); mtx_leave(foo);"
32 * This is _not_ ok:
33 * "mtx_enter(foo); mtx_enter(bar); mtx_leave(foo); mtx_leave(bar);"
34 */
35
36/*
37 * To prevent lock ordering problems with the kernel lock, we need to
38 * make sure we block all interrupts that can grab the kernel lock.
39 * The simplest way to achieve this is to make sure mutexes always
40 * raise the interrupt priority level to the highest level that has
41 * interrupts that grab the kernel lock.
42 */
43#ifdef MULTIPROCESSOR
44#define __MUTEX_IPL(ipl) \
45	(((ipl) < IPL_MPFLOOR) ? IPL_MPFLOOR : (ipl))
46#else
47#define __MUTEX_IPL(ipl) (ipl)
48#endif
49
50#include <machine/mutex.h>
51
52#ifdef __USE_MI_MUTEX
53
54#include <sys/_lock.h>
55
56struct mutex {
57	void *volatile mtx_owner;
58	int mtx_wantipl;
59	int mtx_oldipl;
60#ifdef WITNESS
61	struct lock_object mtx_lock_obj;
62#endif
63};
64
65#ifdef WITNESS
66#define MUTEX_INITIALIZER_FLAGS(ipl, name, flags) \
67	{ NULL, __MUTEX_IPL((ipl)), IPL_NONE, MTX_LO_INITIALIZER(name, flags) }
68#else
69#define MUTEX_INITIALIZER_FLAGS(ipl, name, flags) \
70	{ NULL, __MUTEX_IPL((ipl)), IPL_NONE }
71#endif
72
73void __mtx_init(struct mutex *, int);
74#define _mtx_init(mtx, ipl) __mtx_init((mtx), __MUTEX_IPL((ipl)))
75
76#ifdef DIAGNOSTIC
77#define MUTEX_ASSERT_LOCKED(mtx) do {					\
78	if (((mtx)->mtx_owner != curcpu()) && !(panicstr || db_active))	\
79		panic("mutex %p not held in %s", (mtx), __func__);	\
80} while (0)
81
82#define MUTEX_ASSERT_UNLOCKED(mtx) do {					\
83	if (((mtx)->mtx_owner == curcpu()) && !(panicstr || db_active))	\
84		panic("mutex %p held in %s", (mtx), __func__);		\
85} while (0)
86#else
87#define MUTEX_ASSERT_LOCKED(mtx) do { (void)(mtx); } while (0)
88#define MUTEX_ASSERT_UNLOCKED(mtx) do { (void)(mtx); } while (0)
89#endif
90
91#define MUTEX_LOCK_OBJECT(mtx)	(&(mtx)->mtx_lock_obj)
92#define MUTEX_OLDIPL(mtx)	(mtx)->mtx_oldipl
93
94#endif	/* __USE_MI_MUTEX */
95
96
97#define MTX_LO_FLAGS(flags) \
98	((!((flags) & MTX_NOWITNESS) ? LO_WITNESS : 0) | \
99	 ((flags) & MTX_DUPOK ? LO_DUPOK : 0) | \
100	 LO_INITIALIZED | (LO_CLASS_MUTEX << LO_CLASSSHIFT))
101
102#define __MTX_STRING(x) #x
103#define __MTX_S(x) __MTX_STRING(x)
104#define __MTX_NAME __FILE__ ":" __MTX_S(__LINE__)
105
106#define MTX_LO_INITIALIZER(name, flags) \
107	{ .lo_type = &(const struct lock_type){ .lt_name = __MTX_NAME }, \
108	  .lo_name = (name), \
109	  .lo_flags = MTX_LO_FLAGS(flags) }
110
111#define MTX_NOWITNESS	0x01
112#define MTX_DUPOK	0x02
113
114#define MUTEX_INITIALIZER(ipl) \
115	MUTEX_INITIALIZER_FLAGS(ipl, __MTX_NAME, 0)
116
117/*
118 * Some architectures need to do magic for the ipl, so they need a macro.
119 */
120#ifndef _mtx_init
121void _mtx_init(struct mutex *, int);
122#endif
123
124void	mtx_enter(struct mutex *);
125int	mtx_enter_try(struct mutex *);
126void	mtx_leave(struct mutex *);
127
128#define mtx_init(m, ipl)	mtx_init_flags(m, ipl, NULL, 0)
129
130#define mtx_owned(mtx) \
131	(((mtx)->mtx_owner == curcpu()) || panicstr || db_active)
132
133#ifdef WITNESS
134
135void	_mtx_init_flags(struct mutex *, int, const char *, int,
136	    const struct lock_type *);
137
138#define mtx_init_flags(m, ipl, name, flags) do {			\
139	static const struct lock_type __lock_type = { .lt_name = #m };	\
140	_mtx_init_flags(m, ipl, name, flags, &__lock_type);		\
141} while (0)
142
143#else /* WITNESS */
144
145#define mtx_init_flags(m, ipl, name, flags) do {			\
146	(void)(name); (void)(flags);					\
147	_mtx_init(m, ipl);						\
148} while (0)
149
150#define _mtx_init_flags(m,i,n,f,t)	_mtx_init(m,i)
151
152#endif /* WITNESS */
153
154#if defined(_KERNEL) && defined(DDB)
155
156struct db_mutex {
157	struct cpu_info	*mtx_owner;
158	unsigned long	 mtx_intr_state;
159};
160
161#define DB_MUTEX_INITIALIZER	{ NULL, 0 }
162
163void	db_mtx_enter(struct db_mutex *);
164void	db_mtx_leave(struct db_mutex *);
165
166#endif /* _KERNEL && DDB */
167
168#endif
169