1/* $OpenBSD: mutex.h,v 1.26 2025/12/11 23:34:44 dlg 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 volatile unsigned long 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 { 0, __MUTEX_IPL((ipl)), IPL_NONE, MTX_LO_INITIALIZER(name, flags) }
68#else
69#define MUTEX_INITIALIZER_FLAGS(ipl, name, flags) \
70 { 0, __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#define mtx_curcpu() (unsigned long)curcpu()
77#define mtx_owner(mtx) ((mtx)->mtx_owner & ~1UL)
78
79#ifdef DIAGNOSTIC
80#define MUTEX_ASSERT_LOCKED(mtx) do { \
81 if (mtx_owner(mtx) != mtx_curcpu() && !(panicstr || db_active)) \
82 panic("mutex %p not held in %s", (mtx), __func__); \
83} while (0)
84
85#define MUTEX_ASSERT_UNLOCKED(mtx) do { \
86 if (mtx_owner(mtx) == mtx_curcpu() && !(panicstr || db_active)) \
87 panic("mutex %p held in %s", (mtx), __func__); \
88} while (0)
89#else
90#define MUTEX_ASSERT_LOCKED(mtx) do { (void)(mtx); } while (0)
91#define MUTEX_ASSERT_UNLOCKED(mtx) do { (void)(mtx); } while (0)
92#endif
93
94#define MUTEX_LOCK_OBJECT(mtx) (&(mtx)->mtx_lock_obj)
95#define MUTEX_OLDIPL(mtx) (mtx)->mtx_oldipl
96
97#endif /* __USE_MI_MUTEX */
98
99
100#define MTX_LO_FLAGS(flags) \
101 ((!((flags) & MTX_NOWITNESS) ? LO_WITNESS : 0) | \
102 ((flags) & MTX_DUPOK ? LO_DUPOK : 0) | \
103 LO_INITIALIZED | (LO_CLASS_MUTEX << LO_CLASSSHIFT))
104
105#define __MTX_STRING(x) #x
106#define __MTX_S(x) __MTX_STRING(x)
107#define __MTX_NAME __FILE__ ":" __MTX_S(__LINE__)
108
109#define MTX_LO_INITIALIZER(name, flags) \
110 { .lo_type = &(const struct lock_type){ .lt_name = __MTX_NAME }, \
111 .lo_name = (name), \
112 .lo_flags = MTX_LO_FLAGS(flags) }
113
114#define MTX_NOWITNESS 0x01
115#define MTX_DUPOK 0x02
116
117#define MUTEX_INITIALIZER(ipl) \
118 MUTEX_INITIALIZER_FLAGS(ipl, __MTX_NAME, 0)
119
120/*
121 * Some architectures need to do magic for the ipl, so they need a macro.
122 */
123#ifndef _mtx_init
124void _mtx_init(struct mutex *, int);
125#endif
126
127void mtx_enter(struct mutex *);
128int mtx_enter_try(struct mutex *);
129void mtx_leave(struct mutex *);
130
131#define mtx_init(m, ipl) mtx_init_flags(m, ipl, NULL, 0)
132
133#define mtx_owned(mtx) \
134 ((mtx_owner(mtx) == mtx_curcpu()) || panicstr || db_active)
135
136#ifdef WITNESS
137
138void _mtx_init_flags(struct mutex *, int, const char *, int,
139 const struct lock_type *);
140
141#define mtx_init_flags(m, ipl, name, flags) do { \
142 static const struct lock_type __lock_type = { .lt_name = #m }; \
143 _mtx_init_flags(m, ipl, name, flags, &__lock_type); \
144} while (0)
145
146#else /* WITNESS */
147
148#define mtx_init_flags(m, ipl, name, flags) do { \
149 (void)(name); (void)(flags); \
150 _mtx_init(m, ipl); \
151} while (0)
152
153#define _mtx_init_flags(m,i,n,f,t) _mtx_init(m,i)
154
155#endif /* WITNESS */
156
157#if defined(_KERNEL) && defined(DDB)
158
159struct db_mutex {
160 struct cpu_info *volatile mtx_owner;
161 unsigned long mtx_intr_state;
162};
163
164#define DB_MUTEX_INITIALIZER { NULL, 0 }
165
166void db_mtx_enter(struct db_mutex *);
167void db_mtx_leave(struct db_mutex *);
168
169#endif /* _KERNEL && DDB */
170
171#endif