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It's important to clear mp->owner after calling mutex_unlock() because when CONFIG_DEBUG_MUTEXES is defined the mutex owner is verified in mutex_unlock(). If we set it to NULL this check fails and the lockdep support is immediately disabled.
247 lines
9.3 KiB
C
247 lines
9.3 KiB
C
/*****************************************************************************\
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* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
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* Copyright (C) 2007 The Regents of the University of California.
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* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
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* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
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* UCRL-CODE-235197
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*
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* This file is part of the SPL, Solaris Porting Layer.
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* For details, see <http://github.com/behlendorf/spl/>.
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*
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* The SPL is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*
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* The SPL is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with the SPL. If not, see <http://www.gnu.org/licenses/>.
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\*****************************************************************************/
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#ifndef _SPL_MUTEX_H
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#define _SPL_MUTEX_H
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#include <sys/types.h>
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#include <linux/mutex.h>
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#include <linux/compiler_compat.h>
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typedef enum {
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MUTEX_DEFAULT = 0,
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MUTEX_SPIN = 1,
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MUTEX_ADAPTIVE = 2
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} kmutex_type_t;
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#if defined(HAVE_MUTEX_OWNER) && defined(CONFIG_SMP)
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typedef struct mutex kmutex_t;
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static inline kthread_t *
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mutex_owner(kmutex_t *mp)
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{
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struct thread_info *owner;
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owner = ACCESS_ONCE(mp->owner);
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if (owner)
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return owner->task;
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return NULL;
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}
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static inline int
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mutex_owned(kmutex_t *mp)
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{
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return (ACCESS_ONCE(mp->owner) == current_thread_info());
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}
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#define MUTEX_HELD(mp) mutex_owned(mp)
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#define MUTEX_NOT_HELD(mp) (!MUTEX_HELD(mp))
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#undef mutex_init
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#define mutex_init(mp, name, type, ibc) \
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({ \
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static struct lock_class_key __key; \
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ASSERT(type == MUTEX_DEFAULT); \
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\
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__mutex_init((mp), #mp, &__key); \
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})
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#undef mutex_destroy
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#define mutex_destroy(mp) \
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({ \
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VERIFY3P(mutex_owner(mp), ==, NULL); \
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})
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#define mutex_tryenter(mp) mutex_trylock(mp)
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#define mutex_enter(mp) mutex_lock(mp)
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/* mutex->owner is not cleared when CONFIG_DEBUG_MUTEXES is set */
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#ifdef CONFIG_DEBUG_MUTEXES
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# define mutex_exit(mp) \
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({ \
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mutex_unlock(mp); \
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(mp)->owner = NULL; \
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})
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#else
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# define mutex_exit(mp) mutex_unlock(mp)
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#endif /* CONFIG_DEBUG_MUTEXES */
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#ifdef HAVE_GPL_ONLY_SYMBOLS
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# define mutex_enter_nested(mp, sc) mutex_lock_nested(mp, sc)
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#else
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# define mutex_enter_nested(mp, sc) mutex_enter(mp)
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#endif /* HAVE_GPL_ONLY_SYMBOLS */
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#else /* HAVE_MUTEX_OWNER */
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typedef struct {
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struct mutex m_mutex;
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kthread_t *m_owner;
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} kmutex_t;
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#ifdef HAVE_TASK_CURR
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extern int spl_mutex_spin_max(void);
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#else /* HAVE_TASK_CURR */
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# define task_curr(owner) 0
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# define spl_mutex_spin_max() 0
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#endif /* HAVE_TASK_CURR */
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#define MUTEX(mp) ((struct mutex *)(mp))
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static inline kthread_t *
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spl_mutex_get_owner(kmutex_t *mp)
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{
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return mp->m_owner;
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}
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static inline void
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spl_mutex_set_owner(kmutex_t *mp)
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{
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unsigned long flags;
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spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
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mp->m_owner = current;
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spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
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}
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static inline void
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spl_mutex_clear_owner(kmutex_t *mp)
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{
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unsigned long flags;
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spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
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mp->m_owner = NULL;
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spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
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}
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static inline kthread_t *
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mutex_owner(kmutex_t *mp)
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{
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unsigned long flags;
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kthread_t *owner;
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spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
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owner = spl_mutex_get_owner(mp);
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spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
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return owner;
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}
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#define mutex_owned(mp) (mutex_owner(mp) == current)
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#define MUTEX_HELD(mp) mutex_owned(mp)
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#define MUTEX_NOT_HELD(mp) (!MUTEX_HELD(mp))
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/*
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* The following functions must be a #define and not static inline.
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* This ensures that the native linux mutex functions (lock/unlock)
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* will be correctly located in the users code which is important
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* for the built in kernel lock analysis tools
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*/
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#undef mutex_init
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#define mutex_init(mp, name, type, ibc) \
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({ \
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static struct lock_class_key __key; \
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ASSERT(type == MUTEX_DEFAULT); \
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\
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__mutex_init(MUTEX(mp), #mp, &__key); \
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spl_mutex_clear_owner(mp); \
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})
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#undef mutex_destroy
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#define mutex_destroy(mp) \
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({ \
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VERIFY3P(mutex_owner(mp), ==, NULL); \
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})
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#define mutex_tryenter(mp) \
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({ \
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int _rc_; \
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\
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if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1) \
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spl_mutex_set_owner(mp); \
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\
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_rc_; \
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})
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/*
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* Adaptive mutexs assume that the lock may be held by a task running
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* on a different cpu. The expectation is that the task will drop the
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* lock before leaving the head of the run queue. So the ideal thing
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* to do is spin until we acquire the lock and avoid a context switch.
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* However it is also possible the task holding the lock yields the
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* processor with out dropping lock. In this case, we know it's going
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* to be a while so we stop spinning and go to sleep waiting for the
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* lock to be available. This should strike the optimum balance
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* between spinning and sleeping waiting for a lock.
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*/
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#define mutex_enter(mp) \
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({ \
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kthread_t *_owner_; \
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int _rc_, _count_; \
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\
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_rc_ = 0; \
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_count_ = 0; \
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_owner_ = mutex_owner(mp); \
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\
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while (_owner_ && task_curr(_owner_) && \
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_count_ <= spl_mutex_spin_max()) { \
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if ((_rc_ = mutex_trylock(MUTEX(mp)))) \
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break; \
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\
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_count_++; \
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} \
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\
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if (!_rc_) \
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mutex_lock(MUTEX(mp)); \
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\
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spl_mutex_set_owner(mp); \
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})
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#define mutex_exit(mp) \
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({ \
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spl_mutex_clear_owner(mp); \
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mutex_unlock(MUTEX(mp)); \
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})
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#ifdef HAVE_GPL_ONLY_SYMBOLS
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# define mutex_enter_nested(mp, sc) \
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({ \
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mutex_lock_nested(MUTEX(mp, sc)); \
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spl_mutex_set_owner(mp); \
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})
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#else
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# define mutex_enter_nested(mp, sc) \
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({ \
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mutex_enter(mp); \
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})
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#endif
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#endif /* HAVE_MUTEX_OWNER */
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int spl_mutex_init(void);
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void spl_mutex_fini(void);
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#endif /* _SPL_MUTEX_H */
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