include/linux/mutex.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * Mutexes: blocking mutual exclusion locks
   4  *
   5  * started by Ingo Molnar:
   6  *
   7  *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
   8  *
   9  * This file contains the main data structure and API definitions.
  10  */
  11 #ifndef __LINUX_MUTEX_H
  12 #define __LINUX_MUTEX_H
  13
  14 #include <asm/current.h>
  15 #include <linux/list.h>
  16 #include <linux/spinlock_types.h>
  17 #include <linux/lockdep.h>
  18 #include <linux/atomic.h>
  19 #include <asm/processor.h>
  20 #include <linux/osq_lock.h>
  21 #include <linux/debug_locks.h>
  22
  23 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  24 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)                  \
  25                 , .dep_map = {                                  \
  26                         .name = #lockname,                      \
  27                         .wait_type_inner = LD_WAIT_SLEEP,       \
  28                 }
  29 #else
  30 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
  31 #endif
  32
  33 #ifndef CONFIG_PREEMPT_RT
  34
  35 /*
  36  * Simple, straightforward mutexes with strict semantics:
  37  *
  38  * - only one task can hold the mutex at a time
  39  * - only the owner can unlock the mutex
  40  * - multiple unlocks are not permitted
  41  * - recursive locking is not permitted
  42  * - a mutex object must be initialized via the API
  43  * - a mutex object must not be initialized via memset or copying
  44  * - task may not exit with mutex held
  45  * - memory areas where held locks reside must not be freed
  46  * - held mutexes must not be reinitialized
  47  * - mutexes may not be used in hardware or software interrupt
  48  *   contexts such as tasklets and timers
  49  *
  50  * These semantics are fully enforced when DEBUG_MUTEXES is
  51  * enabled. Furthermore, besides enforcing the above rules, the mutex
  52  * debugging code also implements a number of additional features
  53  * that make lock debugging easier and faster:
  54  *
  55  * - uses symbolic names of mutexes, whenever they are printed in debug output
  56  * - point-of-acquire tracking, symbolic lookup of function names
  57  * - list of all locks held in the system, printout of them
  58  * - owner tracking
  59  * - detects self-recursing locks and prints out all relevant info
  60  * - detects multi-task circular deadlocks and prints out all affected
  61  *   locks and tasks (and only those tasks)
  62  */
  63 struct mutex {
  64         atomic_long_t           owner;
  65         raw_spinlock_t          wait_lock;
  66 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
  67         struct optimistic_spin_queue osq; /* Spinner MCS lock */
  68 #endif
  69         struct list_head        wait_list;
  70 #ifdef CONFIG_DEBUG_MUTEXES
  71         void                    *magic;
  72 #endif
  73 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  74         struct lockdep_map      dep_map;
  75 #endif
  76 };
  77
  78 #ifdef CONFIG_DEBUG_MUTEXES
  79
  80 #define __DEBUG_MUTEX_INITIALIZER(lockname)                             \
  81         , .magic = &lockname
  82
  83 extern void mutex_destroy(struct mutex *lock);
  84
  85 #else
  86
  87 # define __DEBUG_MUTEX_INITIALIZER(lockname)
  88
  89 static inline void mutex_destroy(struct mutex *lock) {}
  90
  91 #endif
  92
  93 /**
  94  * mutex_init - initialize the mutex
  95  * @mutex: the mutex to be initialized
  96  *
  97  * Initialize the mutex to unlocked state.
  98  *
  99  * It is not allowed to initialize an already locked mutex.
 100  */
 101 #define mutex_init(mutex)                                               \
 102 do {                                                                    \
 103         static struct lock_class_key __key;                             \
 104                                                                         \
 105         __mutex_init((mutex), #mutex, &__key);                          \
 106 } while (0)
 107
 108 #define __MUTEX_INITIALIZER(lockname) \
 109                 { .owner = ATOMIC_LONG_INIT(0) \
 110                 , .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
 111                 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
 112                 __DEBUG_MUTEX_INITIALIZER(lockname) \
 113                 __DEP_MAP_MUTEX_INITIALIZER(lockname) }
 114
 115 #define DEFINE_MUTEX(mutexname) \
 116         struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
 117
 118 extern void __mutex_init(struct mutex *lock, const char *name,
 119                          struct lock_class_key *key);
 120
 121 /**
 122  * mutex_is_locked - is the mutex locked
 123  * @lock: the mutex to be queried
 124  *
 125  * Returns true if the mutex is locked, false if unlocked.
 126  */
 127 extern bool mutex_is_locked(struct mutex *lock);
 128
 129 #else /* !CONFIG_PREEMPT_RT */
 130 /*
 131  * Preempt-RT variant based on rtmutexes.
 132  */
 133 #include <linux/rtmutex.h>
 134
 135 struct mutex {
 136         struct rt_mutex_base    rtmutex;
 137 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 138         struct lockdep_map      dep_map;
 139 #endif
 140 };
 141
 142 #define __MUTEX_INITIALIZER(mutexname)                                  \
 143 {                                                                       \
 144         .rtmutex = __RT_MUTEX_BASE_INITIALIZER(mutexname.rtmutex)       \
 145         __DEP_MAP_MUTEX_INITIALIZER(mutexname)                          \
 146 }
 147
 148 #define DEFINE_MUTEX(mutexname)                                         \
 149         struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
 150
 151 extern void __mutex_rt_init(struct mutex *lock, const char *name,
 152                             struct lock_class_key *key);
 153 extern int mutex_trylock(struct mutex *lock);
 154
 155 static inline void mutex_destroy(struct mutex *lock) { }
 156
 157 #define mutex_is_locked(l)      rt_mutex_base_is_locked(&(l)->rtmutex)
 158
 159 #define __mutex_init(mutex, name, key)                  \
 160 do {                                                    \
 161         rt_mutex_base_init(&(mutex)->rtmutex);          \
 162         __mutex_rt_init((mutex), name, key);            \
 163 } while (0)
 164
 165 #define mutex_init(mutex)                               \
 166 do {                                                    \
 167         static struct lock_class_key __key;             \
 168                                                         \
 169         __mutex_init((mutex), #mutex, &__key);          \
 170 } while (0)
 171 #endif /* CONFIG_PREEMPT_RT */
 172
 173 /*
 174  * See kernel/locking/mutex.c for detailed documentation of these APIs.
 175  * Also see Documentation/locking/mutex-design.rst.
 176  */
 177 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 178 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
 179 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
 180
 181 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
 182                                         unsigned int subclass);
 183 extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
 184                                         unsigned int subclass);
 185 extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
 186
 187 #define mutex_lock(lock) mutex_lock_nested(lock, 0)
 188 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
 189 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
 190 #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
 191
 192 #define mutex_lock_nest_lock(lock, nest_lock)                           \
 193 do {                                                                    \
 194         typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
 195         _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map);             \
 196 } while (0)
 197
 198 #else
 199 extern void mutex_lock(struct mutex *lock);
 200 extern int __must_check mutex_lock_interruptible(struct mutex *lock);
 201 extern int __must_check mutex_lock_killable(struct mutex *lock);
 202 extern void mutex_lock_io(struct mutex *lock);
 203
 204 # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
 205 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
 206 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
 207 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
 208 # define mutex_lock_io_nested(lock, subclass) mutex_lock_io(lock)
 209 #endif
 210
 211 /*
 212  * NOTE: mutex_trylock() follows the spin_trylock() convention,
 213  *       not the down_trylock() convention!
 214  *
 215  * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
 216  */
 217 extern int mutex_trylock(struct mutex *lock);
 218 extern void mutex_unlock(struct mutex *lock);
 219
 220 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
 221
 222 #endif /* __LINUX_MUTEX_H */