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/*****************************************************************************\
* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
* Copyright (C) 2007 The Regents of the University of California.
* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
* UCRL-CODE-235197
*
* This file is part of the SPL, Solaris Porting Layer.
* For details, see <http://github.com/behlendorf/spl/>.
*
* The SPL is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
* The SPL is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License along
* with the SPL. If not, see <http://www.gnu.org/licenses/>.
\*****************************************************************************/
#ifndef _SPL_MUTEX_H
#define _SPL_MUTEX_H
#include <sys/types.h>
#include <linux/mutex.h>
#include <linux/compiler_compat.h>
typedef enum {
MUTEX_DEFAULT = 0,
MUTEX_SPIN = 1,
MUTEX_ADAPTIVE = 2
} kmutex_type_t;
#if defined(HAVE_MUTEX_OWNER) && defined(CONFIG_SMP) && !defined(CONFIG_DEBUG_MUTEXES)
/*
* We define a 1-field struct rather than a straight typedef to enforce type
* safety.
*/
typedef struct {
struct mutex m;
} kmutex_t;
static inline kthread_t *
mutex_owner(kmutex_t *mp)
{
#if defined(HAVE_MUTEX_OWNER_TASK_STRUCT)
return ACCESS_ONCE(mp->m.owner);
#else
struct thread_info *owner = ACCESS_ONCE(mp->m.owner);
if (owner)
return owner->task;
return NULL;
#endif
}
#define mutex_owned(mp) (mutex_owner(mp) == current)
#define MUTEX_HELD(mp) mutex_owned(mp)
#define MUTEX_NOT_HELD(mp) (!MUTEX_HELD(mp))
#undef mutex_init
#define mutex_init(mp, name, type, ibc) \
({ \
static struct lock_class_key __key; \
ASSERT(type == MUTEX_DEFAULT); \
\
__mutex_init(&(mp)->m, #mp, &__key); \
})
#undef mutex_destroy
#define mutex_destroy(mp) \
({ \
VERIFY3P(mutex_owner(mp), ==, NULL); \
})
#define mutex_tryenter(mp) mutex_trylock(&(mp)->m)
#define mutex_enter(mp) \
({ \
ASSERT3P(mutex_owner(mp), !=, current); \
mutex_lock(&(mp)->m); \
})
#define mutex_exit(mp) mutex_unlock(&(mp)->m)
#ifdef HAVE_GPL_ONLY_SYMBOLS
# define mutex_enter_nested(mp, sc) mutex_lock_nested(&(mp)->m, sc)
#else
# define mutex_enter_nested(mp, sc) mutex_enter(mp)
#endif /* HAVE_GPL_ONLY_SYMBOLS */
#else /* HAVE_MUTEX_OWNER */
typedef struct {
struct mutex m_mutex;
kthread_t *m_owner;
} kmutex_t;
#ifdef HAVE_TASK_CURR
extern int spl_mutex_spin_max(void);
#else /* HAVE_TASK_CURR */
# define task_curr(owner) 0
# define spl_mutex_spin_max() 0
#endif /* HAVE_TASK_CURR */
#define MUTEX(mp) (&((mp)->m_mutex))
static inline void
spl_mutex_set_owner(kmutex_t *mp)
{
mp->m_owner = current;
}
static inline void
spl_mutex_clear_owner(kmutex_t *mp)
{
mp->m_owner = NULL;
}
#define mutex_owner(mp) (ACCESS_ONCE((mp)->m_owner))
#define mutex_owned(mp) (mutex_owner(mp) == current)
#define MUTEX_HELD(mp) mutex_owned(mp)
#define MUTEX_NOT_HELD(mp) (!MUTEX_HELD(mp))
/*
* The following functions must be a #define and not static inline.
* This ensures that the native linux mutex functions (lock/unlock)
* will be correctly located in the users code which is important
* for the built in kernel lock analysis tools
*/
#undef mutex_init
#define mutex_init(mp, name, type, ibc) \
({ \
static struct lock_class_key __key; \
ASSERT(type == MUTEX_DEFAULT); \
\
__mutex_init(MUTEX(mp), #mp, &__key); \
spl_mutex_clear_owner(mp); \
})
#undef mutex_destroy
#define mutex_destroy(mp) \
({ \
VERIFY3P(mutex_owner(mp), ==, NULL); \
})
#define mutex_tryenter(mp) \
({ \
int _rc_; \
\
if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1) \
spl_mutex_set_owner(mp); \
\
_rc_; \
})
/*
* Adaptive mutexs assume that the lock may be held by a task running
* on a different cpu. The expectation is that the task will drop the
* lock before leaving the head of the run queue. So the ideal thing
* to do is spin until we acquire the lock and avoid a context switch.
* However it is also possible the task holding the lock yields the
* processor with out dropping lock. In this case, we know it's going
* to be a while so we stop spinning and go to sleep waiting for the
* lock to be available. This should strike the optimum balance
* between spinning and sleeping waiting for a lock.
*/
#define mutex_enter(mp) \
({ \
kthread_t *_owner_; \
int _rc_, _count_; \
\
_rc_ = 0; \
_count_ = 0; \
_owner_ = mutex_owner(mp); \
ASSERT3P(_owner_, !=, current); \
\
while (_owner_ && task_curr(_owner_) && \
_count_ <= spl_mutex_spin_max()) { \
if ((_rc_ = mutex_trylock(MUTEX(mp)))) \
break; \
\
_count_++; \
} \
\
if (!_rc_) \
mutex_lock(MUTEX(mp)); \
\
spl_mutex_set_owner(mp); \
})
#define mutex_exit(mp) \
({ \
spl_mutex_clear_owner(mp); \
mutex_unlock(MUTEX(mp)); \
})
#ifdef HAVE_GPL_ONLY_SYMBOLS
# define mutex_enter_nested(mp, sc) \
({ \
mutex_lock_nested(MUTEX(mp), sc); \
spl_mutex_set_owner(mp); \
})
#else
# define mutex_enter_nested(mp, sc) \
({ \
mutex_enter(mp); \
})
#endif
#endif /* HAVE_MUTEX_OWNER */
int spl_mutex_init(void);
void spl_mutex_fini(void);
#endif /* _SPL_MUTEX_H */
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