FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/include/os/linux/spl/sys/mutex.h

     /*
      *  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.
      *
     *  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/sched.h>
    #include <linux/mutex.h>
    #include <linux/lockdep.h>
    #include <linux/compiler_compat.h>
    
    typedef enum {
            MUTEX_DEFAULT   = 0,
            MUTEX_SPIN      = 1,
            MUTEX_ADAPTIVE  = 2,
            MUTEX_NOLOCKDEP = 3
    } kmutex_type_t;
    
    typedef struct {
            struct mutex            m_mutex;
            spinlock_t              m_lock; /* used for serializing mutex_exit */
            kthread_t               *m_owner;
    #ifdef CONFIG_LOCKDEP
            kmutex_type_t           m_type;
    #endif /* CONFIG_LOCKDEP */
    } kmutex_t;
    
    #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)         (READ_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))
    
    #ifdef CONFIG_LOCKDEP
    static inline void
    spl_mutex_set_type(kmutex_t *mp, kmutex_type_t type)
    {
            mp->m_type = type;
    }
    static inline void
    spl_mutex_lockdep_off_maybe(kmutex_t *mp)                       \
    {                                                               \
            if (mp && mp->m_type == MUTEX_NOLOCKDEP)                \
                    lockdep_off();                                  \
    }
    static inline void
    spl_mutex_lockdep_on_maybe(kmutex_t *mp)                        \
    {                                                               \
            if (mp && mp->m_type == MUTEX_NOLOCKDEP)                \
                    lockdep_on();                                   \
    }
    #else  /* CONFIG_LOCKDEP */
    #define spl_mutex_set_type(mp, type)
    #define spl_mutex_lockdep_off_maybe(mp)
    #define spl_mutex_lockdep_on_maybe(mp)
    #endif /* CONFIG_LOCKDEP */
    
    /*
     * 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 || type == MUTEX_NOLOCKDEP); \
                                                                   \
           __mutex_init(MUTEX(mp), (name) ? (#name) : (#mp), &__key); \
           spin_lock_init(&(mp)->m_lock);                          \
           spl_mutex_clear_owner(mp);                              \
           spl_mutex_set_type(mp, type);                           \
   }
   
   #undef mutex_destroy
   #define mutex_destroy(mp)                                       \
   {                                                               \
           VERIFY3P(mutex_owner(mp), ==, NULL);                    \
   }
   
   #define mutex_tryenter(mp)                                      \
   /* CSTYLED */                                                           \
   ({                                                              \
           int _rc_;                                               \
                                                                   \
           spl_mutex_lockdep_off_maybe(mp);                        \
           if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1)             \
                   spl_mutex_set_owner(mp);                        \
           spl_mutex_lockdep_on_maybe(mp);                         \
                                                                   \
           _rc_;                                                   \
   })
   
   #define NESTED_SINGLE 1
   
   #ifdef CONFIG_DEBUG_LOCK_ALLOC
   #define mutex_enter_nested(mp, subclass)                        \
   {                                                               \
           ASSERT3P(mutex_owner(mp), !=, current);                 \
           spl_mutex_lockdep_off_maybe(mp);                        \
           mutex_lock_nested(MUTEX(mp), (subclass));               \
           spl_mutex_lockdep_on_maybe(mp);                         \
           spl_mutex_set_owner(mp);                                \
   }
   #else /* CONFIG_DEBUG_LOCK_ALLOC */
   #define mutex_enter_nested(mp, subclass)                        \
   {                                                               \
           ASSERT3P(mutex_owner(mp), !=, current);                 \
           spl_mutex_lockdep_off_maybe(mp);                        \
           mutex_lock(MUTEX(mp));                                  \
           spl_mutex_lockdep_on_maybe(mp);                         \
           spl_mutex_set_owner(mp);                                \
   }
   #endif /*  CONFIG_DEBUG_LOCK_ALLOC */
   
   #define mutex_enter(mp) mutex_enter_nested((mp), 0)
   
   /*
    * The reason for the spinlock:
    *
    * The Linux mutex is designed with a fast-path/slow-path design such that it
    * does not guarantee serialization upon itself, allowing a race where latter
    * acquirers finish mutex_unlock before former ones.
    *
    * The race renders it unsafe to be used for serializing the freeing of an
    * object in which the mutex is embedded, where the latter acquirer could go
    * on to free the object while the former one is still doing mutex_unlock and
    * causing memory corruption.
    *
    * However, there are many places in ZFS where the mutex is used for
    * serializing object freeing, and the code is shared among other OSes without
    * this issue. Thus, we need the spinlock to force the serialization on
    * mutex_exit().
    *
    * See http://lwn.net/Articles/575477/ for the information about the race.
    */
   #define mutex_exit(mp)                                          \
   {                                                               \
           spl_mutex_clear_owner(mp);                              \
           spin_lock(&(mp)->m_lock);                               \
           spl_mutex_lockdep_off_maybe(mp);                        \
           mutex_unlock(MUTEX(mp));                                \
           spl_mutex_lockdep_on_maybe(mp);                         \
           spin_unlock(&(mp)->m_lock);                             \
           /* NOTE: do not dereference mp after this point */      \
   }
   
   #endif /* _SPL_MUTEX_H */

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