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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>.
8 * This file is part of the SPL, Solaris Porting Layer.
9 * For details, see <http://zfsonlinux.org/>.
11 * The SPL is free software; you can redistribute it and/or modify it
12 * under the terms of the GNU General Public License as published by the
13 * Free Software Foundation; either version 2 of the License, or (at your
14 * option) any later version.
16 * The SPL is distributed in the hope that it will be useful, but WITHOUT
17 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
18 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
21 * You should have received a copy of the GNU General Public License along
22 * with the SPL. If not, see <http://www.gnu.org/licenses/>.
28 #include <sys/types.h>
29 #include <linux/mutex.h>
30 #include <linux/compiler_compat.h>
31 #include <linux/lockdep.h>
42 spinlock_t m_lock
; /* used for serializing mutex_exit */
46 #endif /* CONFIG_LOCKDEP */
49 #define MUTEX(mp) (&((mp)->m_mutex))
52 spl_mutex_set_owner(kmutex_t
*mp
)
54 mp
->m_owner
= current
;
58 spl_mutex_clear_owner(kmutex_t
*mp
)
63 #define mutex_owner(mp) (ACCESS_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))
70 spl_mutex_set_type(kmutex_t
*mp
, kmutex_type_t type
)
75 spl_mutex_lockdep_off_maybe(kmutex_t
*mp
) \
77 if (mp
&& mp
->m_type
== MUTEX_NOLOCKDEP
) \
81 spl_mutex_lockdep_on_maybe(kmutex_t
*mp
) \
83 if (mp
&& mp
->m_type
== MUTEX_NOLOCKDEP
) \
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 */
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
99 #define mutex_init(mp, name, type, ibc) \
101 static struct lock_class_key __key; \
102 ASSERT(type == MUTEX_DEFAULT || type == MUTEX_NOLOCKDEP); \
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); \
111 #define mutex_destroy(mp) \
113 VERIFY3P(mutex_owner(mp), ==, NULL); \
117 #define mutex_tryenter(mp) \
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); \
130 #ifdef CONFIG_DEBUG_LOCK_ALLOC
131 #define mutex_enter_nested(mp, subclass) \
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); \
139 #else /* CONFIG_DEBUG_LOCK_ALLOC */
140 #define mutex_enter_nested(mp, subclass) \
142 ASSERT3P(mutex_owner(mp), !=, current); \
143 spl_mutex_lockdep_off_maybe(mp); \
144 mutex_lock(MUTEX(mp)); \
145 spl_mutex_lockdep_on_maybe(mp); \
146 spl_mutex_set_owner(mp); \
148 #endif /* CONFIG_DEBUG_LOCK_ALLOC */
150 #define mutex_enter(mp) mutex_enter_nested((mp), 0)
153 * The reason for the spinlock:
155 * The Linux mutex is designed with a fast-path/slow-path design such that it
156 * does not guarantee serialization upon itself, allowing a race where latter
157 * acquirers finish mutex_unlock before former ones.
159 * The race renders it unsafe to be used for serializing the freeing of an
160 * object in which the mutex is embedded, where the latter acquirer could go
161 * on to free the object while the former one is still doing mutex_unlock and
162 * causing memory corruption.
164 * However, there are many places in ZFS where the mutex is used for
165 * serializing object freeing, and the code is shared among other OSes without
166 * this issue. Thus, we need the spinlock to force the serialization on
169 * See http://lwn.net/Articles/575477/ for the information about the race.
171 #define mutex_exit(mp) \
173 spl_mutex_clear_owner(mp); \
174 spin_lock(&(mp)->m_lock); \
175 spl_mutex_lockdep_off_maybe(mp); \
176 mutex_unlock(MUTEX(mp)); \
177 spl_mutex_lockdep_on_maybe(mp); \
178 spin_unlock(&(mp)->m_lock); \
179 /* NOTE: do not dereference mp after this point */ \
182 int spl_mutex_init(void);
183 void spl_mutex_fini(void);
185 #endif /* _SPL_MUTEX_H */