![Jean Delvare](/assets/img/avatar_default.png)
The non-debug variant of mutex_destroy is a no-op, currently implemented as a macro which does nothing. This approach fails to check the type of the parameter, so an error would only show when debugging gets enabled. Using an inline function instead, offers type checking for earlier bug catching. Signed-off-by: Jean Delvare <khali@linux-fr.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20110716174200.41002352@endymion.delvare Signed-off-by: Ingo Molnar <mingo@elte.hu>
177 lines
5.4 KiB
C
177 lines
5.4 KiB
C
/*
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* Mutexes: blocking mutual exclusion locks
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*
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* started by Ingo Molnar:
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*
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* Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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*
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* This file contains the main data structure and API definitions.
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*/
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#ifndef __LINUX_MUTEX_H
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#define __LINUX_MUTEX_H
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#include <linux/list.h>
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#include <linux/spinlock_types.h>
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#include <linux/linkage.h>
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#include <linux/lockdep.h>
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#include <asm/atomic.h>
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/*
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* Simple, straightforward mutexes with strict semantics:
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*
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* - only one task can hold the mutex at a time
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* - only the owner can unlock the mutex
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* - multiple unlocks are not permitted
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* - recursive locking is not permitted
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* - a mutex object must be initialized via the API
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* - a mutex object must not be initialized via memset or copying
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* - task may not exit with mutex held
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* - memory areas where held locks reside must not be freed
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* - held mutexes must not be reinitialized
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* - mutexes may not be used in hardware or software interrupt
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* contexts such as tasklets and timers
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*
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* These semantics are fully enforced when DEBUG_MUTEXES is
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* enabled. Furthermore, besides enforcing the above rules, the mutex
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* debugging code also implements a number of additional features
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* that make lock debugging easier and faster:
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*
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* - uses symbolic names of mutexes, whenever they are printed in debug output
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* - point-of-acquire tracking, symbolic lookup of function names
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* - list of all locks held in the system, printout of them
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* - owner tracking
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* - detects self-recursing locks and prints out all relevant info
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* - detects multi-task circular deadlocks and prints out all affected
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* locks and tasks (and only those tasks)
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*/
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struct mutex {
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/* 1: unlocked, 0: locked, negative: locked, possible waiters */
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atomic_t count;
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spinlock_t wait_lock;
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struct list_head wait_list;
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#if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP)
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struct task_struct *owner;
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#endif
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#ifdef CONFIG_DEBUG_MUTEXES
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const char *name;
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void *magic;
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#endif
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lockdep_map dep_map;
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#endif
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};
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/*
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* This is the control structure for tasks blocked on mutex,
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* which resides on the blocked task's kernel stack:
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*/
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struct mutex_waiter {
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struct list_head list;
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struct task_struct *task;
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#ifdef CONFIG_DEBUG_MUTEXES
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void *magic;
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#endif
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};
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#ifdef CONFIG_DEBUG_MUTEXES
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# include <linux/mutex-debug.h>
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#else
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# define __DEBUG_MUTEX_INITIALIZER(lockname)
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/**
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* mutex_init - initialize the mutex
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* @mutex: the mutex to be initialized
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*
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* Initialize the mutex to unlocked state.
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*
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* It is not allowed to initialize an already locked mutex.
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*/
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# define mutex_init(mutex) \
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do { \
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static struct lock_class_key __key; \
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\
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__mutex_init((mutex), #mutex, &__key); \
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} while (0)
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static inline void mutex_destroy(struct mutex *lock) {}
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#endif
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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# define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
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, .dep_map = { .name = #lockname }
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#else
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# define __DEP_MAP_MUTEX_INITIALIZER(lockname)
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#endif
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#define __MUTEX_INITIALIZER(lockname) \
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{ .count = ATOMIC_INIT(1) \
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, .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
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, .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
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__DEBUG_MUTEX_INITIALIZER(lockname) \
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__DEP_MAP_MUTEX_INITIALIZER(lockname) }
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#define DEFINE_MUTEX(mutexname) \
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struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
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extern void __mutex_init(struct mutex *lock, const char *name,
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struct lock_class_key *key);
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/**
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* mutex_is_locked - is the mutex locked
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* @lock: the mutex to be queried
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*
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* Returns 1 if the mutex is locked, 0 if unlocked.
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*/
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static inline int mutex_is_locked(struct mutex *lock)
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{
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return atomic_read(&lock->count) != 1;
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}
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/*
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* See kernel/mutex.c for detailed documentation of these APIs.
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* Also see Documentation/mutex-design.txt.
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*/
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
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extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
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extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
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unsigned int subclass);
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extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
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unsigned int subclass);
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#define mutex_lock(lock) mutex_lock_nested(lock, 0)
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#define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
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#define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
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#define mutex_lock_nest_lock(lock, nest_lock) \
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do { \
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typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
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_mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \
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} while (0)
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#else
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extern void mutex_lock(struct mutex *lock);
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extern int __must_check mutex_lock_interruptible(struct mutex *lock);
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extern int __must_check mutex_lock_killable(struct mutex *lock);
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# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
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# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
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# define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
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# define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
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#endif
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/*
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* NOTE: mutex_trylock() follows the spin_trylock() convention,
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* not the down_trylock() convention!
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*
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* Returns 1 if the mutex has been acquired successfully, and 0 on contention.
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*/
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extern int mutex_trylock(struct mutex *lock);
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extern void mutex_unlock(struct mutex *lock);
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extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
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#ifndef CONFIG_HAVE_ARCH_MUTEX_CPU_RELAX
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#define arch_mutex_cpu_relax() cpu_relax()
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#endif
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#endif
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