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 /* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Mutexes: blocking mutual exclusion locks
  *
  * started by Ingo Molnar:
  *
  *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  *
  * This file contains the main data structure and API definitions.
  */
 #ifndef __LINUX_MUTEX_H
 #define __LINUX_MUTEX_H
 
 #include <asm/current.h>
 #include <linux/list.h>
 #include <linux/spinlock_types.h>
 #include <linux/lockdep.h>
 #include <linux/atomic.h>
 #include <asm/processor.h>
 #include <linux/osq_lock.h>
 #include <linux/debug_locks.h>
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)          \
         , .dep_map = {                  \
             .name = #lockname,          \
             .wait_type_inner = LD_WAIT_SLEEP,   \
         }
 #else
 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
 #endif
 
 #ifndef CONFIG_PREEMPT_RT
 
 /*
  * Simple, straightforward mutexes with strict semantics:
  *
  * - only one task can hold the mutex at a time
  * - only the owner can unlock the mutex
  * - multiple unlocks are not permitted
  * - recursive locking is not permitted
  * - a mutex object must be initialized via the API
  * - a mutex object must not be initialized via memset or copying
  * - task may not exit with mutex held
  * - memory areas where held locks reside must not be freed
  * - held mutexes must not be reinitialized
  * - mutexes may not be used in hardware or software interrupt
  *   contexts such as tasklets and timers
  *
  * These semantics are fully enforced when DEBUG_MUTEXES is
  * enabled. Furthermore, besides enforcing the above rules, the mutex
  * debugging code also implements a number of additional features
  * that make lock debugging easier and faster:
  *
  * - uses symbolic names of mutexes, whenever they are printed in debug output
  * - point-of-acquire tracking, symbolic lookup of function names
  * - list of all locks held in the system, printout of them
  * - owner tracking
  * - detects self-recursing locks and prints out all relevant info
  * - detects multi-task circular deadlocks and prints out all affected
  *   locks and tasks (and only those tasks)
  */
 struct mutex {
     atomic_long_t       owner;
     raw_spinlock_t      wait_lock;
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
     struct optimistic_spin_queue osq; /* Spinner MCS lock */
 #endif
     struct list_head    wait_list;
 #ifdef CONFIG_DEBUG_MUTEXES
     void            *magic;
 #endif
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
     struct lockdep_map  dep_map;
 #endif
 };
 
 #ifdef CONFIG_DEBUG_MUTEXES
 
 #define __DEBUG_MUTEX_INITIALIZER(lockname)             \
     , .magic = &lockname
 
 extern void mutex_destroy(struct mutex *lock);
 
 #else
 
 # define __DEBUG_MUTEX_INITIALIZER(lockname)
 
 static inline void mutex_destroy(struct mutex *lock) {}
 
 #endif
 
 /**
  * mutex_init - initialize the mutex
  * @mutex: the mutex to be initialized
  *
  * Initialize the mutex to unlocked state.
  *
  * It is not allowed to initialize an already locked mutex.
  */
 #define mutex_init(mutex)                       \
 do {                                    \
     static struct lock_class_key __key;             \
                                     \
     __mutex_init((mutex), #mutex, &__key);              \
 } while (0)
 
 #define __MUTEX_INITIALIZER(lockname) \
         { .owner = ATOMIC_LONG_INIT(0) \
         , .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
         , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
         __DEBUG_MUTEX_INITIALIZER(lockname) \
         __DEP_MAP_MUTEX_INITIALIZER(lockname) }
 
 #define DEFINE_MUTEX(mutexname) \
     struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
 
 extern void __mutex_init(struct mutex *lock, const char *name,
              struct lock_class_key *key);
 
 /**
  * mutex_is_locked - is the mutex locked
  * @lock: the mutex to be queried
  *
  * Returns true if the mutex is locked, false if unlocked.
  */
 extern bool mutex_is_locked(struct mutex *lock);
 
 #else /* !CONFIG_PREEMPT_RT */
 /*
  * Preempt-RT variant based on rtmutexes.
  */
 #include <linux/rtmutex.h>
 
 struct mutex {
     struct rt_mutex_base    rtmutex;
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
     struct lockdep_map  dep_map;
 #endif
 };
 
 #define __MUTEX_INITIALIZER(mutexname)                  \
 {                                   \
     .rtmutex = __RT_MUTEX_BASE_INITIALIZER(mutexname.rtmutex)   \
     __DEP_MAP_MUTEX_INITIALIZER(mutexname)              \
 }
 
 #define DEFINE_MUTEX(mutexname)                     \
     struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
 
 extern void __mutex_rt_init(struct mutex *lock, const char *name,
                 struct lock_class_key *key);
 extern int mutex_trylock(struct mutex *lock);
 
 static inline void mutex_destroy(struct mutex *lock) { }
 
 #define mutex_is_locked(l)  rt_mutex_base_is_locked(&(l)->rtmutex)
 
 #define __mutex_init(mutex, name, key)          \
 do {                            \
     rt_mutex_base_init(&(mutex)->rtmutex);      \
     __mutex_rt_init((mutex), name, key);        \
 } while (0)
 
 #define mutex_init(mutex)               \
 do {                            \
     static struct lock_class_key __key;     \
                             \
     __mutex_init((mutex), #mutex, &__key);      \
 } while (0)
 #endif /* CONFIG_PREEMPT_RT */
 
 /*
  * See kernel/locking/mutex.c for detailed documentation of these APIs.
  * Also see Documentation/locking/mutex-design.rst.
  */
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
 
 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
                     unsigned int subclass);
 extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
                     unsigned int subclass);
 extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
 
 #define mutex_lock(lock) mutex_lock_nested(lock, 0)
 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
 #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
 
 #define mutex_lock_nest_lock(lock, nest_lock)               \
 do {                                    \
     typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
     _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map);     \
 } while (0)
 
 #else
 extern void mutex_lock(struct mutex *lock);
 extern int __must_check mutex_lock_interruptible(struct mutex *lock);
 extern int __must_check mutex_lock_killable(struct mutex *lock);
 extern void mutex_lock_io(struct mutex *lock);
 
 # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
 # define mutex_lock_io_nested(lock, subclass) mutex_lock_io(lock)
 #endif
 
 /*
  * NOTE: mutex_trylock() follows the spin_trylock() convention,
  *       not the down_trylock() convention!
  *
  * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
  */
 extern int mutex_trylock(struct mutex *lock);
 extern void mutex_unlock(struct mutex *lock);
 
 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
 
 #endif /* __LINUX_MUTEX_H */

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