LCOV - code coverage report
Current view: top level - lkbce/include/linux - mutex.h (source / functions) Hit Total Coverage
Test: coverage.info Lines: 1 1 100.0 %
Date: 2017-01-25 Functions: 0 0 -

          Line data    Source code
       1             : /*
       2             :  * Mutexes: blocking mutual exclusion locks
       3             :  *
       4             :  * started by Ingo Molnar:
       5             :  *
       6             :  *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
       7             :  *
       8             :  * This file contains the main data structure and API definitions.
       9             :  */
      10             : #ifndef __LINUX_MUTEX_H
      11             : #define __LINUX_MUTEX_H
      12             : 
      13             : #include <linux/list.h>
      14             : #include <linux/spinlock_types.h>
      15             : #include <linux/linkage.h>
      16             : #include <linux/lockdep.h>
      17             : 
      18             : #include <asm/atomic.h>
      19             : 
      20             : /*
      21             :  * Simple, straightforward mutexes with strict semantics:
      22             :  *
      23             :  * - only one task can hold the mutex at a time
      24             :  * - only the owner can unlock the mutex
      25             :  * - multiple unlocks are not permitted
      26             :  * - recursive locking is not permitted
      27             :  * - a mutex object must be initialized via the API
      28             :  * - a mutex object must not be initialized via memset or copying
      29             :  * - task may not exit with mutex held
      30             :  * - memory areas where held locks reside must not be freed
      31             :  * - held mutexes must not be reinitialized
      32             :  * - mutexes may not be used in hardware or software interrupt
      33             :  *   contexts such as tasklets and timers
      34             :  *
      35             :  * These semantics are fully enforced when DEBUG_MUTEXES is
      36             :  * enabled. Furthermore, besides enforcing the above rules, the mutex
      37             :  * debugging code also implements a number of additional features
      38             :  * that make lock debugging easier and faster:
      39             :  *
      40             :  * - uses symbolic names of mutexes, whenever they are printed in debug output
      41             :  * - point-of-acquire tracking, symbolic lookup of function names
      42             :  * - list of all locks held in the system, printout of them
      43             :  * - owner tracking
      44             :  * - detects self-recursing locks and prints out all relevant info
      45             :  * - detects multi-task circular deadlocks and prints out all affected
      46             :  *   locks and tasks (and only those tasks)
      47             :  */
      48             : struct mutex {
      49             :         /* 1: unlocked, 0: locked, negative: locked, possible waiters */
      50             :         atomic_t                count;
      51             :         spinlock_t              wait_lock;
      52             :         struct list_head        wait_list;
      53             : #if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP)
      54             :         struct thread_info      *owner;
      55             : #endif
      56             : #ifdef CONFIG_DEBUG_MUTEXES
      57             :         const char              *name;
      58             :         void                    *magic;
      59             : #endif
      60             : #ifdef CONFIG_DEBUG_LOCK_ALLOC
      61             :         struct lockdep_map      dep_map;
      62             : #endif
      63             : };
      64             : 
      65             : /*
      66             :  * This is the control structure for tasks blocked on mutex,
      67             :  * which resides on the blocked task's kernel stack:
      68             :  */
      69             : struct mutex_waiter {
      70             :         struct list_head        list;
      71             :         struct task_struct      *task;
      72             : #ifdef CONFIG_DEBUG_MUTEXES
      73             :         void                    *magic;
      74             : #endif
      75             : };
      76             : 
      77             : #ifdef CONFIG_DEBUG_MUTEXES
      78             : # include <linux/mutex-debug.h>
      79             : #else
      80             : # define __DEBUG_MUTEX_INITIALIZER(lockname)
      81             : # define mutex_init(mutex) \
      82             : do {                                                    \
      83             :         static struct lock_class_key __key;             \
      84             :                                                         \
      85             :         __mutex_init((mutex), #mutex, &__key);              \
      86             : } while (0)
      87             : # define mutex_destroy(mutex)                           do { } while (0)
      88             : #endif
      89             : 
      90             : #ifdef CONFIG_DEBUG_LOCK_ALLOC
      91             : # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
      92             :                 , .dep_map = { .name = #lockname }
      93             : #else
      94             : # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
      95             : #endif
      96             : 
      97             : #define __MUTEX_INITIALIZER(lockname) \
      98             :                 { .count = ATOMIC_INIT(1) \
      99             :                 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
     100             :                 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
     101             :                 __DEBUG_MUTEX_INITIALIZER(lockname) \
     102             :                 __DEP_MAP_MUTEX_INITIALIZER(lockname) }
     103             : 
     104             : #define DEFINE_MUTEX(mutexname) \
     105             :         struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
     106             : 
     107             : extern void __mutex_init(struct mutex *lock, const char *name,
     108             :                          struct lock_class_key *key);
     109             : 
     110             : /**
     111             :  * mutex_is_locked - is the mutex locked
     112             :  * @lock: the mutex to be queried
     113             :  *
     114             :  * Returns 1 if the mutex is locked, 0 if unlocked.
     115             :  */
     116             : static inline int mutex_is_locked(struct mutex *lock)
     117             : {
     118             :         return atomic_read(&lock->count) != 1;
     119             : }
     120             : 
     121             : /*
     122             :  * See kernel/mutex.c for detailed documentation of these APIs.
     123             :  * Also see Documentation/mutex-design.txt.
     124             :  */
     125             : #ifdef CONFIG_DEBUG_LOCK_ALLOC
     126             : extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
     127             : extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
     128             :                                         unsigned int subclass);
     129             : extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
     130             :                                         unsigned int subclass);
     131             : 
     132             : #define mutex_lock(lock) mutex_lock_nested(lock, 0)
     133             : #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
     134             : #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
     135             : #else
     136             : extern void mutex_lock(struct mutex *lock);
     137             : extern int __must_check mutex_lock_interruptible(struct mutex *lock);
     138             : extern int __must_check mutex_lock_killable(struct mutex *lock);
     139             : 
     140             : # define mutex_lock_nested(lock, subclass) mutex_lock(lock)
     141             : # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
     142             : # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
     143             : #endif
     144             : 
     145             : /*
     146             :  * NOTE: mutex_trylock() follows the spin_trylock() convention,
     147             :  *       not the down_trylock() convention!
     148             :  *
     149             :  * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
     150             :  */
     151             : extern int mutex_trylock(struct mutex *lock);
     152             : extern void mutex_unlock(struct mutex *lock);
     153             : extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
     154           1 : 
     155             : #endif

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