1 /*
2 * Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
3 * Copyright (C) 2007 The Regents of the University of California.
4 * Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
5 * Written by Brian Behlendorf <behlendorf1@llnl.gov>.
6 * UCRL-CODE-235197
7 *
8 * This file is part of the SPL, Solaris Porting Layer.
9 *
10 * The SPL is free software; you can redistribute it and/or modify it
11 * under the terms of the GNU General Public License as published by the
12 * Free Software Foundation; either version 2 of the License, or (at your
13 * option) any later version.
14 *
15 * The SPL is distributed in the hope that it will be useful, but WITHOUT
16 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
17 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 * for more details.
19 *
20 * You should have received a copy of the GNU General Public License along
21 * with the SPL. If not, see <http://www.gnu.org/licenses/>.
22 */
23
24 #ifndef _SPL_MUTEX_H
25 #define _SPL_MUTEX_H
26
27 #include <sys/types.h>
28 #include <linux/sched.h>
29 #include <linux/mutex.h>
30 #include <linux/lockdep.h>
31 #include <linux/compiler_compat.h>
32
33 typedef enum {
34 MUTEX_DEFAULT = 0,
35 MUTEX_SPIN = 1,
36 MUTEX_ADAPTIVE = 2,
37 MUTEX_NOLOCKDEP = 3
38 } kmutex_type_t;
39
40 typedef struct {
41 struct mutex m_mutex;
42 spinlock_t m_lock; /* used for serializing mutex_exit */
43 kthread_t *m_owner;
44 #ifdef CONFIG_LOCKDEP
45 kmutex_type_t m_type;
46 #endif /* CONFIG_LOCKDEP */
47 } kmutex_t;
48
49 #define MUTEX(mp) (&((mp)->m_mutex))
50
51 static inline void
spl_mutex_set_owner(kmutex_t * mp)52 spl_mutex_set_owner(kmutex_t *mp)
53 {
54 mp->m_owner = current;
55 }
56
57 static inline void
spl_mutex_clear_owner(kmutex_t * mp)58 spl_mutex_clear_owner(kmutex_t *mp)
59 {
60 mp->m_owner = NULL;
61 }
62
63 #define mutex_owner(mp) (READ_ONCE((mp)->m_owner))
64 #define mutex_owned(mp) (mutex_owner(mp) == current)
65 #define MUTEX_HELD(mp) mutex_owned(mp)
66 #define MUTEX_NOT_HELD(mp) (!MUTEX_HELD(mp))
67
68 #ifdef CONFIG_LOCKDEP
69 static inline void
spl_mutex_set_type(kmutex_t * mp,kmutex_type_t type)70 spl_mutex_set_type(kmutex_t *mp, kmutex_type_t type)
71 {
72 mp->m_type = type;
73 }
74 static inline void
spl_mutex_lockdep_off_maybe(kmutex_t * mp)75 spl_mutex_lockdep_off_maybe(kmutex_t *mp) \
76 { \
77 if (mp && mp->m_type == MUTEX_NOLOCKDEP) \
78 lockdep_off(); \
79 }
80 static inline void
spl_mutex_lockdep_on_maybe(kmutex_t * mp)81 spl_mutex_lockdep_on_maybe(kmutex_t *mp) \
82 { \
83 if (mp && mp->m_type == MUTEX_NOLOCKDEP) \
84 lockdep_on(); \
85 }
86 #else /* CONFIG_LOCKDEP */
87 #define spl_mutex_set_type(mp, type)
88 #define spl_mutex_lockdep_off_maybe(mp)
89 #define spl_mutex_lockdep_on_maybe(mp)
90 #endif /* CONFIG_LOCKDEP */
91
92 /*
93 * The following functions must be a #define and not static inline.
94 * This ensures that the native linux mutex functions (lock/unlock)
95 * will be correctly located in the users code which is important
96 * for the built in kernel lock analysis tools
97 */
98 #undef mutex_init
99 #define mutex_init(mp, name, type, ibc) \
100 { \
101 static struct lock_class_key __key; \
102 ASSERT(type == MUTEX_DEFAULT || type == MUTEX_NOLOCKDEP); \
103 \
104 __mutex_init(MUTEX(mp), (name) ? (#name) : (#mp), &__key); \
105 spin_lock_init(&(mp)->m_lock); \
106 spl_mutex_clear_owner(mp); \
107 spl_mutex_set_type(mp, type); \
108 }
109
110 #undef mutex_destroy
111 #define mutex_destroy(mp) \
112 { \
113 VERIFY3P(mutex_owner(mp), ==, NULL); \
114 }
115
116 #define mutex_tryenter(mp) \
117 /* CSTYLED */ \
118 ({ \
119 int _rc_; \
120 \
121 spl_mutex_lockdep_off_maybe(mp); \
122 if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1) \
123 spl_mutex_set_owner(mp); \
124 spl_mutex_lockdep_on_maybe(mp); \
125 \
126 _rc_; \
127 })
128
129 #define NESTED_SINGLE 1
130
131 #define mutex_enter_nested(mp, subclass) \
132 { \
133 ASSERT3P(mutex_owner(mp), !=, current); \
134 spl_mutex_lockdep_off_maybe(mp); \
135 mutex_lock_nested(MUTEX(mp), (subclass)); \
136 spl_mutex_lockdep_on_maybe(mp); \
137 spl_mutex_set_owner(mp); \
138 }
139
140 #define mutex_enter_interruptible(mp) \
141 /* CSTYLED */ \
142 ({ \
143 int _rc_; \
144 \
145 ASSERT3P(mutex_owner(mp), !=, current); \
146 spl_mutex_lockdep_off_maybe(mp); \
147 _rc_ = mutex_lock_interruptible(MUTEX(mp)); \
148 spl_mutex_lockdep_on_maybe(mp); \
149 if (!_rc_) { \
150 spl_mutex_set_owner(mp); \
151 } \
152 \
153 _rc_; \
154 })
155
156 #define mutex_enter(mp) mutex_enter_nested((mp), 0)
157
158 /*
159 * The reason for the spinlock:
160 *
161 * The Linux mutex is designed with a fast-path/slow-path design such that it
162 * does not guarantee serialization upon itself, allowing a race where latter
163 * acquirers finish mutex_unlock before former ones.
164 *
165 * The race renders it unsafe to be used for serializing the freeing of an
166 * object in which the mutex is embedded, where the latter acquirer could go
167 * on to free the object while the former one is still doing mutex_unlock and
168 * causing memory corruption.
169 *
170 * However, there are many places in ZFS where the mutex is used for
171 * serializing object freeing, and the code is shared among other OSes without
172 * this issue. Thus, we need the spinlock to force the serialization on
173 * mutex_exit().
174 *
175 * See http://lwn.net/Articles/575477/ for the information about the race.
176 */
177 #define mutex_exit(mp) \
178 { \
179 ASSERT3P(mutex_owner(mp), ==, current); \
180 spl_mutex_clear_owner(mp); \
181 spin_lock(&(mp)->m_lock); \
182 spl_mutex_lockdep_off_maybe(mp); \
183 mutex_unlock(MUTEX(mp)); \
184 spl_mutex_lockdep_on_maybe(mp); \
185 spin_unlock(&(mp)->m_lock); \
186 /* NOTE: do not dereference mp after this point */ \
187 }
188
189 #endif /* _SPL_MUTEX_H */
190