235 lines
7 KiB
C
235 lines
7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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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 <asm/current.h>
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#include <linux/list.h>
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#include <linux/spinlock_types.h>
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#include <linux/lockdep.h>
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#include <linux/atomic.h>
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#include <asm/processor.h>
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#include <linux/osq_lock.h>
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#include <linux/debug_locks.h>
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struct ww_acquire_ctx;
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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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atomic_long_t owner;
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spinlock_t wait_lock;
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#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
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struct optimistic_spin_queue osq; /* Spinner MCS lock */
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#endif
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struct list_head wait_list;
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#ifdef CONFIG_DEBUG_MUTEXES
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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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* Internal helper function; C doesn't allow us to hide it :/
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*
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* DO NOT USE (outside of mutex code).
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*/
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static inline struct task_struct *__mutex_owner(struct mutex *lock)
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{
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return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
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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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struct ww_acquire_ctx *ww_ctx;
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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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#define __DEBUG_MUTEX_INITIALIZER(lockname) \
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, .magic = &lockname
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extern void mutex_destroy(struct mutex *lock);
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#else
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# define __DEBUG_MUTEX_INITIALIZER(lockname)
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static inline void mutex_destroy(struct mutex *lock) {}
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#endif
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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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#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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{ .owner = ATOMIC_LONG_INIT(0) \
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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 true if the mutex is locked, false if unlocked.
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*/
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static inline bool mutex_is_locked(struct mutex *lock)
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{
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/*
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* XXX think about spin_is_locked
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*/
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return __mutex_owner(lock) != NULL;
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}
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/*
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* See kernel/locking/mutex.c for detailed documentation of these APIs.
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* Also see Documentation/locking/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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extern void mutex_lock_io_nested(struct mutex *lock, 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_io(lock) mutex_lock_io_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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extern void mutex_lock_io(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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# define mutex_lock_io_nested(lock, subclass) 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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/*
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* These values are chosen such that FAIL and SUCCESS match the
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* values of the regular mutex_trylock().
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*/
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enum mutex_trylock_recursive_enum {
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MUTEX_TRYLOCK_FAILED = 0,
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MUTEX_TRYLOCK_SUCCESS = 1,
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MUTEX_TRYLOCK_RECURSIVE,
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};
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/**
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* mutex_trylock_recursive - trylock variant that allows recursive locking
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* @lock: mutex to be locked
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*
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* This function should not be used, _ever_. It is purely for hysterical GEM
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* raisins, and once those are gone this will be removed.
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*
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* Returns:
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* - MUTEX_TRYLOCK_FAILED - trylock failed,
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* - MUTEX_TRYLOCK_SUCCESS - lock acquired,
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* - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
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*/
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static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
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mutex_trylock_recursive(struct mutex *lock)
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{
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if (unlikely(__mutex_owner(lock) == current))
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return MUTEX_TRYLOCK_RECURSIVE;
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return mutex_trylock(lock);
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}
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#endif /* __LINUX_MUTEX_H */
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