LCOV - code coverage report
Current view: top level - include/linux - mutex.h (source / functions) Hit Total Coverage
Test: combined.info Lines: 1 1 100.0 %
Date: 2022-04-01 14:17:54 Functions: 0 0 -
Branches: 0 6 0.0 %

           Branch data     Line data    Source code
       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                 :            : struct ww_acquire_ctx;
      24                 :            : 
      25                 :            : /*
      26                 :            :  * Simple, straightforward mutexes with strict semantics:
      27                 :            :  *
      28                 :            :  * - only one task can hold the mutex at a time
      29                 :            :  * - only the owner can unlock the mutex
      30                 :            :  * - multiple unlocks are not permitted
      31                 :            :  * - recursive locking is not permitted
      32                 :            :  * - a mutex object must be initialized via the API
      33                 :            :  * - a mutex object must not be initialized via memset or copying
      34                 :            :  * - task may not exit with mutex held
      35                 :            :  * - memory areas where held locks reside must not be freed
      36                 :            :  * - held mutexes must not be reinitialized
      37                 :            :  * - mutexes may not be used in hardware or software interrupt
      38                 :            :  *   contexts such as tasklets and timers
      39                 :            :  *
      40                 :            :  * These semantics are fully enforced when DEBUG_MUTEXES is
      41                 :            :  * enabled. Furthermore, besides enforcing the above rules, the mutex
      42                 :            :  * debugging code also implements a number of additional features
      43                 :            :  * that make lock debugging easier and faster:
      44                 :            :  *
      45                 :            :  * - uses symbolic names of mutexes, whenever they are printed in debug output
      46                 :            :  * - point-of-acquire tracking, symbolic lookup of function names
      47                 :            :  * - list of all locks held in the system, printout of them
      48                 :            :  * - owner tracking
      49                 :            :  * - detects self-recursing locks and prints out all relevant info
      50                 :            :  * - detects multi-task circular deadlocks and prints out all affected
      51                 :            :  *   locks and tasks (and only those tasks)
      52                 :            :  */
      53                 :            : struct mutex {
      54                 :            :         atomic_long_t           owner;
      55                 :            :         spinlock_t              wait_lock;
      56                 :            : #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
      57                 :            :         struct optimistic_spin_queue osq; /* Spinner MCS lock */
      58                 :            : #endif
      59                 :            :         struct list_head        wait_list;
      60                 :            : #ifdef CONFIG_DEBUG_MUTEXES
      61                 :            :         void                    *magic;
      62                 :            : #endif
      63                 :            : #ifdef CONFIG_DEBUG_LOCK_ALLOC
      64                 :            :         struct lockdep_map      dep_map;
      65                 :            : #endif
      66                 :            : };
      67                 :            : 
      68                 :            : /*
      69                 :            :  * This is the control structure for tasks blocked on mutex,
      70                 :            :  * which resides on the blocked task's kernel stack:
      71                 :            :  */
      72                 :            : struct mutex_waiter {
      73                 :            :         struct list_head        list;
      74                 :            :         struct task_struct      *task;
      75                 :            :         struct ww_acquire_ctx   *ww_ctx;
      76                 :            : #ifdef CONFIG_DEBUG_MUTEXES
      77                 :            :         void                    *magic;
      78                 :            : #endif
      79                 :            : };
      80                 :            : 
      81                 :            : #ifdef CONFIG_DEBUG_MUTEXES
      82                 :            : 
      83                 :            : #define __DEBUG_MUTEX_INITIALIZER(lockname)                             \
      84                 :            :         , .magic = &lockname
      85                 :            : 
      86                 :            : extern void mutex_destroy(struct mutex *lock);
      87                 :            : 
      88                 :            : #else
      89                 :            : 
      90                 :            : # define __DEBUG_MUTEX_INITIALIZER(lockname)
      91                 :            : 
      92   [ #  #  #  #  :        253 : static inline void mutex_destroy(struct mutex *lock) {}
                   #  # ]
      93                 :            : 
      94                 :            : #endif
      95                 :            : 
      96                 :            : /**
      97                 :            :  * mutex_init - initialize the mutex
      98                 :            :  * @mutex: the mutex to be initialized
      99                 :            :  *
     100                 :            :  * Initialize the mutex to unlocked state.
     101                 :            :  *
     102                 :            :  * It is not allowed to initialize an already locked mutex.
     103                 :            :  */
     104                 :            : #define mutex_init(mutex)                                               \
     105                 :            : do {                                                                    \
     106                 :            :         static struct lock_class_key __key;                             \
     107                 :            :                                                                         \
     108                 :            :         __mutex_init((mutex), #mutex, &__key);                              \
     109                 :            : } while (0)
     110                 :            : 
     111                 :            : #ifdef CONFIG_DEBUG_LOCK_ALLOC
     112                 :            : # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
     113                 :            :                 , .dep_map = { .name = #lockname }
     114                 :            : #else
     115                 :            : # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
     116                 :            : #endif
     117                 :            : 
     118                 :            : #define __MUTEX_INITIALIZER(lockname) \
     119                 :            :                 { .owner = ATOMIC_LONG_INIT(0) \
     120                 :            :                 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
     121                 :            :                 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
     122                 :            :                 __DEBUG_MUTEX_INITIALIZER(lockname) \
     123                 :            :                 __DEP_MAP_MUTEX_INITIALIZER(lockname) }
     124                 :            : 
     125                 :            : #define DEFINE_MUTEX(mutexname) \
     126                 :            :         struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
     127                 :            : 
     128                 :            : extern void __mutex_init(struct mutex *lock, const char *name,
     129                 :            :                          struct lock_class_key *key);
     130                 :            : 
     131                 :            : /**
     132                 :            :  * mutex_is_locked - is the mutex locked
     133                 :            :  * @lock: the mutex to be queried
     134                 :            :  *
     135                 :            :  * Returns true if the mutex is locked, false if unlocked.
     136                 :            :  */
     137                 :            : extern bool mutex_is_locked(struct mutex *lock);
     138                 :            : 
     139                 :            : /*
     140                 :            :  * See kernel/locking/mutex.c for detailed documentation of these APIs.
     141                 :            :  * Also see Documentation/locking/mutex-design.rst.
     142                 :            :  */
     143                 :            : #ifdef CONFIG_DEBUG_LOCK_ALLOC
     144                 :            : extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
     145                 :            : extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
     146                 :            : 
     147                 :            : extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
     148                 :            :                                         unsigned int subclass);
     149                 :            : extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
     150                 :            :                                         unsigned int subclass);
     151                 :            : extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
     152                 :            : 
     153                 :            : #define mutex_lock(lock) mutex_lock_nested(lock, 0)
     154                 :            : #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
     155                 :            : #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
     156                 :            : #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
     157                 :            : 
     158                 :            : #define mutex_lock_nest_lock(lock, nest_lock)                           \
     159                 :            : do {                                                                    \
     160                 :            :         typecheck(struct lockdep_map *, &(nest_lock)->dep_map);  \
     161                 :            :         _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map);              \
     162                 :            : } while (0)
     163                 :            : 
     164                 :            : #else
     165                 :            : extern void mutex_lock(struct mutex *lock);
     166                 :            : extern int __must_check mutex_lock_interruptible(struct mutex *lock);
     167                 :            : extern int __must_check mutex_lock_killable(struct mutex *lock);
     168                 :            : extern void mutex_lock_io(struct mutex *lock);
     169                 :            : 
     170                 :            : # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
     171                 :            : # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
     172                 :            : # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
     173                 :            : # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
     174                 :            : # define mutex_lock_io_nested(lock, subclass) mutex_lock(lock)
     175                 :            : #endif
     176                 :            : 
     177                 :            : /*
     178                 :            :  * NOTE: mutex_trylock() follows the spin_trylock() convention,
     179                 :            :  *       not the down_trylock() convention!
     180                 :            :  *
     181                 :            :  * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
     182                 :            :  */
     183                 :            : extern int mutex_trylock(struct mutex *lock);
     184                 :            : extern void mutex_unlock(struct mutex *lock);
     185                 :            : 
     186                 :            : extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
     187                 :            : 
     188                 :            : /*
     189                 :            :  * These values are chosen such that FAIL and SUCCESS match the
     190                 :            :  * values of the regular mutex_trylock().
     191                 :            :  */
     192                 :            : enum mutex_trylock_recursive_enum {
     193                 :            :         MUTEX_TRYLOCK_FAILED    = 0,
     194                 :            :         MUTEX_TRYLOCK_SUCCESS   = 1,
     195                 :            :         MUTEX_TRYLOCK_RECURSIVE,
     196                 :            : };
     197                 :            : 
     198                 :            : /**
     199                 :            :  * mutex_trylock_recursive - trylock variant that allows recursive locking
     200                 :            :  * @lock: mutex to be locked
     201                 :            :  *
     202                 :            :  * This function should not be used, _ever_. It is purely for hysterical GEM
     203                 :            :  * raisins, and once those are gone this will be removed.
     204                 :            :  *
     205                 :            :  * Returns:
     206                 :            :  *  - MUTEX_TRYLOCK_FAILED    - trylock failed,
     207                 :            :  *  - MUTEX_TRYLOCK_SUCCESS   - lock acquired,
     208                 :            :  *  - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
     209                 :            :  */
     210                 :            : extern /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
     211                 :            : mutex_trylock_recursive(struct mutex *lock);
     212                 :            : 
     213                 :            : #endif /* __LINUX_MUTEX_H */

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