kernel/locking/rtmutex_api.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * rtmutex API
  */
 #include <linux/spinlock.h>
 #include <linux/export.h>

 #define RT_MUTEX_BUILD_MUTEX
 #include "rtmutex.c"

 /*
  * Max number of times we'll walk the boosting chain:
  */
 int max_lock_depth = 1024;

 /*
  * Debug aware fast / slowpath lock,trylock,unlock
  *
  * The atomic acquire/release ops are compiled away, when either the
  * architecture does not support cmpxchg or when debugging is enabled.
  */
 static __always_inline int __rt_mutex_lock_common(struct rt_mutex *lock,
 						  unsigned int state,
 						  unsigned int subclass)
 {
 	int ret;

 	might_sleep();
 	mutex_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
 	ret = __rt_mutex_lock(&lock->rtmutex, state);
 	if (ret)
 		mutex_release(&lock->dep_map, _RET_IP_);
 	return ret;
 }

 void rt_mutex_base_init(struct rt_mutex_base *rtb)
 {
 	__rt_mutex_base_init(rtb);
 }
 EXPORT_SYMBOL(rt_mutex_base_init);

 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 /**
  * rt_mutex_lock_nested - lock a rt_mutex
  *
  * @lock: the rt_mutex to be locked
  * @subclass: the lockdep subclass
  */
 void __sched rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int subclass)
 {
 	__rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass);
 }
 EXPORT_SYMBOL_GPL(rt_mutex_lock_nested);

 #else /* !CONFIG_DEBUG_LOCK_ALLOC */

 /**
  * rt_mutex_lock - lock a rt_mutex
  *
  * @lock: the rt_mutex to be locked
  */
 void __sched rt_mutex_lock(struct rt_mutex *lock)
 {
 	__rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0);
 }
 EXPORT_SYMBOL_GPL(rt_mutex_lock);
 #endif

 /**
  * rt_mutex_lock_interruptible - lock a rt_mutex interruptible
  *
  * @lock:		the rt_mutex to be locked
  *
  * Returns:
  *  0		on success
  * -EINTR	when interrupted by a signal
  */
 int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock)
 {
 	return __rt_mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0);
 }
 EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);

 /**
  * rt_mutex_trylock - try to lock a rt_mutex
  *
  * @lock:	the rt_mutex to be locked
  *
  * This function can only be called in thread context. It's safe to call it
  * from atomic regions, but not from hard or soft interrupt context.
  *
  * Returns:
  *  1 on success
  *  0 on contention
  */
 int __sched rt_mutex_trylock(struct rt_mutex *lock)
 {
 	int ret;

 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES) && WARN_ON_ONCE(!in_task()))
 		return 0;

 	ret = __rt_mutex_trylock(&lock->rtmutex);
 	if (ret)
 		mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);

 	return ret;
 }
 EXPORT_SYMBOL_GPL(rt_mutex_trylock);

 /**
  * rt_mutex_unlock - unlock a rt_mutex
  *
  * @lock: the rt_mutex to be unlocked
  */
 void __sched rt_mutex_unlock(struct rt_mutex *lock)
 {
 	mutex_release(&lock->dep_map, _RET_IP_);
 	__rt_mutex_unlock(&lock->rtmutex);
 }
 EXPORT_SYMBOL_GPL(rt_mutex_unlock);

 /*
  * Futex variants, must not use fastpath.
  */
 int __sched rt_mutex_futex_trylock(struct rt_mutex_base *lock)
 {
 	return rt_mutex_slowtrylock(lock);
 }

 int __sched __rt_mutex_futex_trylock(struct rt_mutex_base *lock)
 {
 	return __rt_mutex_slowtrylock(lock);
 }

 /**
  * __rt_mutex_futex_unlock - Futex variant, that since futex variants
  * do not use the fast-path, can be simple and will not need to retry.
  *
  * @lock:	The rt_mutex to be unlocked
  * @wqh:	The wake queue head from which to get the next lock waiter
  */
 bool __sched __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
 				     struct rt_wake_q_head *wqh)
 {
 	lockdep_assert_held(&lock->wait_lock);

 	debug_rt_mutex_unlock(lock);

 	if (!rt_mutex_has_waiters(lock)) {
 		lock->owner = NULL;
 		return false; /* done */
 	}

 	/*
 	 * We've already deboosted, mark_wakeup_next_waiter() will
 	 * retain preempt_disabled when we drop the wait_lock, to
 	 * avoid inversion prior to the wakeup.  preempt_disable()
 	 * therein pairs with rt_mutex_postunlock().
 	 */
 	mark_wakeup_next_waiter(wqh, lock);

 	return true; /* call postunlock() */
 }

 void __sched rt_mutex_futex_unlock(struct rt_mutex_base *lock)
 {
 	DEFINE_RT_WAKE_Q(wqh);
 	unsigned long flags;
 	bool postunlock;

 	raw_spin_lock_irqsave(&lock->wait_lock, flags);
 	postunlock = __rt_mutex_futex_unlock(lock, &wqh);
 	raw_spin_unlock_irqrestore(&lock->wait_lock, flags);

 	if (postunlock)
 		rt_mutex_postunlock(&wqh);
 }

 /**
  * __rt_mutex_init - initialize the rt_mutex
  *
  * @lock:	The rt_mutex to be initialized
  * @name:	The lock name used for debugging
  * @key:	The lock class key used for debugging
  *
  * Initialize the rt_mutex to unlocked state.
  *
  * Initializing of a locked rt_mutex is not allowed
  */
 void __sched __rt_mutex_init(struct rt_mutex *lock, const char *name,
 			     struct lock_class_key *key)
 {
 	debug_check_no_locks_freed((void *)lock, sizeof(*lock));
 	__rt_mutex_base_init(&lock->rtmutex);
 	lockdep_init_map_wait(&lock->dep_map, name, key, 0, LD_WAIT_SLEEP);
 }
 EXPORT_SYMBOL_GPL(__rt_mutex_init);

 /**
  * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
  *				proxy owner
  *
  * @lock:	the rt_mutex to be locked
  * @proxy_owner:the task to set as owner
  *
  * No locking. Caller has to do serializing itself
  *
  * Special API call for PI-futex support. This initializes the rtmutex and
  * assigns it to @proxy_owner. Concurrent operations on the rtmutex are not
  * possible at this point because the pi_state which contains the rtmutex
  * is not yet visible to other tasks.
  */
 void __sched rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
 					struct task_struct *proxy_owner)
 {
 	static struct lock_class_key pi_futex_key;

 	__rt_mutex_base_init(lock);
 	/*
 	 * On PREEMPT_RT the futex hashbucket spinlock becomes 'sleeping'
 	 * and rtmutex based. That causes a lockdep false positive, because
 	 * some of the futex functions invoke spin_unlock(&hb->lock) with
 	 * the wait_lock of the rtmutex associated to the pi_futex held.
 	 * spin_unlock() in turn takes wait_lock of the rtmutex on which
 	 * the spinlock is based, which makes lockdep notice a lock
 	 * recursion. Give the futex/rtmutex wait_lock a separate key.
 	 */
 	lockdep_set_class(&lock->wait_lock, &pi_futex_key);
 	rt_mutex_set_owner(lock, proxy_owner);
 }

 /**
  * rt_mutex_proxy_unlock - release a lock on behalf of owner
  *
  * @lock:	the rt_mutex to be locked
  *
  * No locking. Caller has to do serializing itself
  *
  * Special API call for PI-futex support. This just cleans up the rtmutex
  * (debugging) state. Concurrent operations on this rt_mutex are not
  * possible because it belongs to the pi_state which is about to be freed
  * and it is not longer visible to other tasks.
  */
 void __sched rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
 {
 	debug_rt_mutex_proxy_unlock(lock);
 	rt_mutex_set_owner(lock, NULL);
 }

 /**
  * __rt_mutex_start_proxy_lock() - Start lock acquisition for another task
  * @lock:		the rt_mutex to take
  * @waiter:		the pre-initialized rt_mutex_waiter
  * @task:		the task to prepare
  *
  * Starts the rt_mutex acquire; it enqueues the @waiter and does deadlock
  * detection. It does not wait, see rt_mutex_wait_proxy_lock() for that.
  *
  * NOTE: does _NOT_ remove the @waiter on failure; must either call
  * rt_mutex_wait_proxy_lock() or rt_mutex_cleanup_proxy_lock() after this.
  *
  * Returns:
  *  0 - task blocked on lock
  *  1 - acquired the lock for task, caller should wake it up
  * <0 - error
  *
  * Special API call for PI-futex support.
  */
 int __sched __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
 					struct rt_mutex_waiter *waiter,
 					struct task_struct *task)
 {
 	int ret;

 	lockdep_assert_held(&lock->wait_lock);

 	if (try_to_take_rt_mutex(lock, task, NULL))
 		return 1;

 	/* We enforce deadlock detection for futexes */
 	ret = task_blocks_on_rt_mutex(lock, waiter, task, NULL,
 				      RT_MUTEX_FULL_CHAINWALK);

 	if (ret && !rt_mutex_owner(lock)) {
 		/*
 		 * Reset the return value. We might have
 		 * returned with -EDEADLK and the owner
 		 * released the lock while we were walking the
 		 * pi chain.  Let the waiter sort it out.
 		 */
 		ret = 0;
 	}

 	return ret;
 }

 /**
  * rt_mutex_start_proxy_lock() - Start lock acquisition for another task
  * @lock:		the rt_mutex to take
  * @waiter:		the pre-initialized rt_mutex_waiter
  * @task:		the task to prepare
  *
  * Starts the rt_mutex acquire; it enqueues the @waiter and does deadlock
  * detection. It does not wait, see rt_mutex_wait_proxy_lock() for that.
  *
  * NOTE: unlike __rt_mutex_start_proxy_lock this _DOES_ remove the @waiter
  * on failure.
  *
  * Returns:
  *  0 - task blocked on lock
  *  1 - acquired the lock for task, caller should wake it up
  * <0 - error
  *
  * Special API call for PI-futex support.
  */
 int __sched rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
 				      struct rt_mutex_waiter *waiter,
 				      struct task_struct *task)
 {
 	int ret;

 	raw_spin_lock_irq(&lock->wait_lock);
 	ret = __rt_mutex_start_proxy_lock(lock, waiter, task);
 	if (unlikely(ret))
 		remove_waiter(lock, waiter);
 	raw_spin_unlock_irq(&lock->wait_lock);

 	return ret;
 }

 /**
  * rt_mutex_wait_proxy_lock() - Wait for lock acquisition
  * @lock:		the rt_mutex we were woken on
  * @to:			the timeout, null if none. hrtimer should already have
  *			been started.
  * @waiter:		the pre-initialized rt_mutex_waiter
  *
  * Wait for the lock acquisition started on our behalf by
  * rt_mutex_start_proxy_lock(). Upon failure, the caller must call
  * rt_mutex_cleanup_proxy_lock().
  *
  * Returns:
  *  0 - success
  * <0 - error, one of -EINTR, -ETIMEDOUT
  *
  * Special API call for PI-futex support
  */
 int __sched rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
 				     struct hrtimer_sleeper *to,
 				     struct rt_mutex_waiter *waiter)
 {
 	int ret;

 	raw_spin_lock_irq(&lock->wait_lock);
 	/* sleep on the mutex */
 	set_current_state(TASK_INTERRUPTIBLE);
 	ret = rt_mutex_slowlock_block(lock, NULL, TASK_INTERRUPTIBLE, to, waiter);
 	/*
 	 * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
 	 * have to fix that up.
 	 */
 	fixup_rt_mutex_waiters(lock);
 	raw_spin_unlock_irq(&lock->wait_lock);

 	return ret;
 }

 /**
  * rt_mutex_cleanup_proxy_lock() - Cleanup failed lock acquisition
  * @lock:		the rt_mutex we were woken on
  * @waiter:		the pre-initialized rt_mutex_waiter
  *
  * Attempt to clean up after a failed __rt_mutex_start_proxy_lock() or
  * rt_mutex_wait_proxy_lock().
  *
  * Unless we acquired the lock; we're still enqueued on the wait-list and can
  * in fact still be granted ownership until we're removed. Therefore we can
  * find we are in fact the owner and must disregard the
  * rt_mutex_wait_proxy_lock() failure.
  *
  * Returns:
  *  true  - did the cleanup, we done.
  *  false - we acquired the lock after rt_mutex_wait_proxy_lock() returned,
  *          caller should disregards its return value.
  *
  * Special API call for PI-futex support
  */
 bool __sched rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
 					 struct rt_mutex_waiter *waiter)
 {
 	bool cleanup = false;

 	raw_spin_lock_irq(&lock->wait_lock);
 	/*
 	 * Do an unconditional try-lock, this deals with the lock stealing
 	 * state where __rt_mutex_futex_unlock() -> mark_wakeup_next_waiter()
 	 * sets a NULL owner.
 	 *
 	 * We're not interested in the return value, because the subsequent
 	 * test on rt_mutex_owner() will infer that. If the trylock succeeded,
 	 * we will own the lock and it will have removed the waiter. If we
 	 * failed the trylock, we're still not owner and we need to remove
 	 * ourselves.
 	 */
 	try_to_take_rt_mutex(lock, current, waiter);
 	/*
 	 * Unless we're the owner; we're still enqueued on the wait_list.
 	 * So check if we became owner, if not, take us off the wait_list.
 	 */
 	if (rt_mutex_owner(lock) != current) {
 		remove_waiter(lock, waiter);
 		cleanup = true;
 	}
 	/*
 	 * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
 	 * have to fix that up.
 	 */
 	fixup_rt_mutex_waiters(lock);

 	raw_spin_unlock_irq(&lock->wait_lock);

 	return cleanup;
 }

 /*
  * Recheck the pi chain, in case we got a priority setting
  *
  * Called from sched_setscheduler
  */
 void __sched rt_mutex_adjust_pi(struct task_struct *task)
 {
 	struct rt_mutex_waiter *waiter;
 	struct rt_mutex_base *next_lock;
 	unsigned long flags;

 	raw_spin_lock_irqsave(&task->pi_lock, flags);

 	waiter = task->pi_blocked_on;
 	if (!waiter || rt_mutex_waiter_equal(waiter, task_to_waiter(task))) {
 		raw_spin_unlock_irqrestore(&task->pi_lock, flags);
 		return;
 	}
 	next_lock = waiter->lock;
 	raw_spin_unlock_irqrestore(&task->pi_lock, flags);

 	/* gets dropped in rt_mutex_adjust_prio_chain()! */
 	get_task_struct(task);

 	rt_mutex_adjust_prio_chain(task, RT_MUTEX_MIN_CHAINWALK, NULL,
 				   next_lock, NULL, task);
 }

 /*
  * Performs the wakeup of the top-waiter and re-enables preemption.
  */
 void __sched rt_mutex_postunlock(struct rt_wake_q_head *wqh)
 {
 	rt_mutex_wake_up_q(wqh);
 }

 #ifdef CONFIG_DEBUG_RT_MUTEXES
 void rt_mutex_debug_task_free(struct task_struct *task)
 {
 	DEBUG_LOCKS_WARN_ON(!RB_EMPTY_ROOT(&task->pi_waiters.rb_root));
 	DEBUG_LOCKS_WARN_ON(task->pi_blocked_on);
 }
 #endif

 #ifdef CONFIG_PREEMPT_RT
 /* Mutexes */
 void __mutex_rt_init(struct mutex *mutex, const char *name,
 		     struct lock_class_key *key)
 {
 	debug_check_no_locks_freed((void *)mutex, sizeof(*mutex));
 	lockdep_init_map_wait(&mutex->dep_map, name, key, 0, LD_WAIT_SLEEP);
 }
 EXPORT_SYMBOL(__mutex_rt_init);

 static __always_inline int __mutex_lock_common(struct mutex *lock,
 					       unsigned int state,
 					       unsigned int subclass,
 					       struct lockdep_map *nest_lock,
 					       unsigned long ip)
 {
 	int ret;

 	might_sleep();
 	mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
 	ret = __rt_mutex_lock(&lock->rtmutex, state);
 	if (ret)
 		mutex_release(&lock->dep_map, ip);
 	else
 		lock_acquired(&lock->dep_map, ip);
 	return ret;
 }

 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 void __sched mutex_lock_nested(struct mutex *lock, unsigned int subclass)
 {
 	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
 }
 EXPORT_SYMBOL_GPL(mutex_lock_nested);

 void __sched _mutex_lock_nest_lock(struct mutex *lock,
 				   struct lockdep_map *nest_lock)
 {
 	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, nest_lock, _RET_IP_);
 }
 EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);

 int __sched mutex_lock_interruptible_nested(struct mutex *lock,
 					    unsigned int subclass)
 {
 	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, subclass, NULL, _RET_IP_);
 }
 EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);

 int __sched mutex_lock_killable_nested(struct mutex *lock,
 					    unsigned int subclass)
 {
 	return __mutex_lock_common(lock, TASK_KILLABLE, subclass, NULL, _RET_IP_);
 }
 EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);

 void __sched mutex_lock_io_nested(struct mutex *lock, unsigned int subclass)
 {
 	int token;

 	might_sleep();

 	token = io_schedule_prepare();
 	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
 	io_schedule_finish(token);
 }
 EXPORT_SYMBOL_GPL(mutex_lock_io_nested);

 #else /* CONFIG_DEBUG_LOCK_ALLOC */

 void __sched mutex_lock(struct mutex *lock)
 {
 	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
 }
 EXPORT_SYMBOL(mutex_lock);

 int __sched mutex_lock_interruptible(struct mutex *lock)
 {
 	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_);
 }
 EXPORT_SYMBOL(mutex_lock_interruptible);

 int __sched mutex_lock_killable(struct mutex *lock)
 {
 	return __mutex_lock_common(lock, TASK_KILLABLE, 0, NULL, _RET_IP_);
 }
 EXPORT_SYMBOL(mutex_lock_killable);

 void __sched mutex_lock_io(struct mutex *lock)
 {
 	int token = io_schedule_prepare();

 	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
 	io_schedule_finish(token);
 }
 EXPORT_SYMBOL(mutex_lock_io);
 #endif /* !CONFIG_DEBUG_LOCK_ALLOC */

 int __sched mutex_trylock(struct mutex *lock)
 {
 	int ret;

 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES) && WARN_ON_ONCE(!in_task()))
 		return 0;

 	ret = __rt_mutex_trylock(&lock->rtmutex);
 	if (ret)
 		mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);

 	return ret;
 }
 EXPORT_SYMBOL(mutex_trylock);

 void __sched mutex_unlock(struct mutex *lock)
 {
 	mutex_release(&lock->dep_map, _RET_IP_);
 	__rt_mutex_unlock(&lock->rtmutex);
 }
 EXPORT_SYMBOL(mutex_unlock);

 #endif /* CONFIG_PREEMPT_RT */
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* rtmutex API
	*/
	#include <linux/spinlock.h>
	#include <linux/export.h>

	#define RT_MUTEX_BUILD_MUTEX
	#include "rtmutex.c"

	/*
	* Max number of times we'll walk the boosting chain:
	*/
	int max_lock_depth = 1024;

	/*
	* Debug aware fast / slowpath lock,trylock,unlock
	*
	* The atomic acquire/release ops are compiled away, when either the
	* architecture does not support cmpxchg or when debugging is enabled.
	*/
	static __always_inline int __rt_mutex_lock_common(struct rt_mutex *lock,
	unsigned int state,
	unsigned int subclass)
	{
	int ret;

	might_sleep();
	mutex_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
	ret = __rt_mutex_lock(&lock->rtmutex, state);
	if (ret)
	mutex_release(&lock->dep_map, _RET_IP_);
	return ret;
	}

	void rt_mutex_base_init(struct rt_mutex_base *rtb)
	{
	__rt_mutex_base_init(rtb);
	}
	EXPORT_SYMBOL(rt_mutex_base_init);

	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	/**
	* rt_mutex_lock_nested - lock a rt_mutex
	*
	* @lock: the rt_mutex to be locked
	* @subclass: the lockdep subclass
	*/
	void __sched rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int subclass)
	{
	__rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass);
	}
	EXPORT_SYMBOL_GPL(rt_mutex_lock_nested);

	#else /* !CONFIG_DEBUG_LOCK_ALLOC */

	/**
	* rt_mutex_lock - lock a rt_mutex
	*
	* @lock: the rt_mutex to be locked
	*/
	void __sched rt_mutex_lock(struct rt_mutex *lock)
	{
	__rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0);
	}
	EXPORT_SYMBOL_GPL(rt_mutex_lock);
	#endif

	/**
	* rt_mutex_lock_interruptible - lock a rt_mutex interruptible
	*
	* @lock: the rt_mutex to be locked
	*
	* Returns:
	* 0 on success
	* -EINTR when interrupted by a signal
	*/
	int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock)
	{
	return __rt_mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0);
	}
	EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);

	/**
	* rt_mutex_trylock - try to lock a rt_mutex
	*
	* @lock: the rt_mutex to be locked
	*
	* This function can only be called in thread context. It's safe to call it
	* from atomic regions, but not from hard or soft interrupt context.
	*
	* Returns:
	* 1 on success
	* 0 on contention
	*/
	int __sched rt_mutex_trylock(struct rt_mutex *lock)
	{
	int ret;

	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES) && WARN_ON_ONCE(!in_task()))
	return 0;

	ret = __rt_mutex_trylock(&lock->rtmutex);
	if (ret)
	mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);

	return ret;
	}
	EXPORT_SYMBOL_GPL(rt_mutex_trylock);

	/**
	* rt_mutex_unlock - unlock a rt_mutex
	*
	* @lock: the rt_mutex to be unlocked
	*/
	void __sched rt_mutex_unlock(struct rt_mutex *lock)
	{
	mutex_release(&lock->dep_map, _RET_IP_);
	__rt_mutex_unlock(&lock->rtmutex);
	}
	EXPORT_SYMBOL_GPL(rt_mutex_unlock);

	/*
	* Futex variants, must not use fastpath.
	*/
	int __sched rt_mutex_futex_trylock(struct rt_mutex_base *lock)
	{
	return rt_mutex_slowtrylock(lock);
	}

	int __sched __rt_mutex_futex_trylock(struct rt_mutex_base *lock)
	{
	return __rt_mutex_slowtrylock(lock);
	}

	/**
	* __rt_mutex_futex_unlock - Futex variant, that since futex variants
	* do not use the fast-path, can be simple and will not need to retry.
	*
	* @lock: The rt_mutex to be unlocked
	* @wqh: The wake queue head from which to get the next lock waiter
	*/
	bool __sched __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
	struct rt_wake_q_head *wqh)
	{
	lockdep_assert_held(&lock->wait_lock);

	debug_rt_mutex_unlock(lock);

	if (!rt_mutex_has_waiters(lock)) {
	lock->owner = NULL;
	return false; /* done */
	}

	/*
	* We've already deboosted, mark_wakeup_next_waiter() will
	* retain preempt_disabled when we drop the wait_lock, to
	* avoid inversion prior to the wakeup. preempt_disable()
	* therein pairs with rt_mutex_postunlock().
	*/
	mark_wakeup_next_waiter(wqh, lock);

	return true; /* call postunlock() */
	}

	void __sched rt_mutex_futex_unlock(struct rt_mutex_base *lock)
	{
	DEFINE_RT_WAKE_Q(wqh);
	unsigned long flags;
	bool postunlock;

	raw_spin_lock_irqsave(&lock->wait_lock, flags);
	postunlock = __rt_mutex_futex_unlock(lock, &wqh);
	raw_spin_unlock_irqrestore(&lock->wait_lock, flags);

	if (postunlock)
	rt_mutex_postunlock(&wqh);
	}

	/**
	* __rt_mutex_init - initialize the rt_mutex
	*
	* @lock: The rt_mutex to be initialized
	* @name: The lock name used for debugging
	* @key: The lock class key used for debugging
	*
	* Initialize the rt_mutex to unlocked state.
	*
	* Initializing of a locked rt_mutex is not allowed
	*/
	void __sched __rt_mutex_init(struct rt_mutex lock, const char name,
	struct lock_class_key *key)
	{
	debug_check_no_locks_freed((void )lock, sizeof(lock));
	__rt_mutex_base_init(&lock->rtmutex);
	lockdep_init_map_wait(&lock->dep_map, name, key, 0, LD_WAIT_SLEEP);
	}
	EXPORT_SYMBOL_GPL(__rt_mutex_init);

	/**
	* rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
	* proxy owner
	*
	* @lock: the rt_mutex to be locked
	* @proxy_owner:the task to set as owner
	*
	* No locking. Caller has to do serializing itself
	*
	* Special API call for PI-futex support. This initializes the rtmutex and
	* assigns it to @proxy_owner. Concurrent operations on the rtmutex are not
	* possible at this point because the pi_state which contains the rtmutex
	* is not yet visible to other tasks.
	*/
	void __sched rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
	struct task_struct *proxy_owner)
	{
	static struct lock_class_key pi_futex_key;

	__rt_mutex_base_init(lock);
	/*
	* On PREEMPT_RT the futex hashbucket spinlock becomes 'sleeping'
	* and rtmutex based. That causes a lockdep false positive, because
	* some of the futex functions invoke spin_unlock(&hb->lock) with
	* the wait_lock of the rtmutex associated to the pi_futex held.
	* spin_unlock() in turn takes wait_lock of the rtmutex on which
	* the spinlock is based, which makes lockdep notice a lock
	* recursion. Give the futex/rtmutex wait_lock a separate key.
	*/
	lockdep_set_class(&lock->wait_lock, &pi_futex_key);
	rt_mutex_set_owner(lock, proxy_owner);
	}

	/**
	* rt_mutex_proxy_unlock - release a lock on behalf of owner
	*
	* @lock: the rt_mutex to be locked
	*
	* No locking. Caller has to do serializing itself
	*
	* Special API call for PI-futex support. This just cleans up the rtmutex
	* (debugging) state. Concurrent operations on this rt_mutex are not
	* possible because it belongs to the pi_state which is about to be freed
	* and it is not longer visible to other tasks.
	*/
	void __sched rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
	{
	debug_rt_mutex_proxy_unlock(lock);
	rt_mutex_set_owner(lock, NULL);
	}

	/**
	* __rt_mutex_start_proxy_lock() - Start lock acquisition for another task
	* @lock: the rt_mutex to take
	* @waiter: the pre-initialized rt_mutex_waiter
	* @task: the task to prepare
	*
	* Starts the rt_mutex acquire; it enqueues the @waiter and does deadlock
	* detection. It does not wait, see rt_mutex_wait_proxy_lock() for that.
	*
	* NOTE: does _NOT_ remove the @waiter on failure; must either call
	* rt_mutex_wait_proxy_lock() or rt_mutex_cleanup_proxy_lock() after this.
	*
	* Returns:
	* 0 - task blocked on lock
	* 1 - acquired the lock for task, caller should wake it up
	* <0 - error
	*
	* Special API call for PI-futex support.
	*/
	int __sched __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
	struct rt_mutex_waiter *waiter,
	struct task_struct *task)
	{
	int ret;

	lockdep_assert_held(&lock->wait_lock);

	if (try_to_take_rt_mutex(lock, task, NULL))
	return 1;

	/* We enforce deadlock detection for futexes */
	ret = task_blocks_on_rt_mutex(lock, waiter, task, NULL,
	RT_MUTEX_FULL_CHAINWALK);

	if (ret && !rt_mutex_owner(lock)) {
	/*
	* Reset the return value. We might have
	* returned with -EDEADLK and the owner
	* released the lock while we were walking the
	* pi chain. Let the waiter sort it out.
	*/
	ret = 0;
	}

	return ret;
	}

	/**
	* rt_mutex_start_proxy_lock() - Start lock acquisition for another task
	* @lock: the rt_mutex to take
	* @waiter: the pre-initialized rt_mutex_waiter
	* @task: the task to prepare
	*
	* Starts the rt_mutex acquire; it enqueues the @waiter and does deadlock
	* detection. It does not wait, see rt_mutex_wait_proxy_lock() for that.
	*
	* NOTE: unlike __rt_mutex_start_proxy_lock this _DOES_ remove the @waiter
	* on failure.
	*
	* Returns:
	* 0 - task blocked on lock
	* 1 - acquired the lock for task, caller should wake it up
	* <0 - error
	*
	* Special API call for PI-futex support.
	*/
	int __sched rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
	struct rt_mutex_waiter *waiter,
	struct task_struct *task)
	{
	int ret;

	raw_spin_lock_irq(&lock->wait_lock);
	ret = __rt_mutex_start_proxy_lock(lock, waiter, task);
	if (unlikely(ret))
	remove_waiter(lock, waiter);
	raw_spin_unlock_irq(&lock->wait_lock);

	return ret;
	}

	/**
	* rt_mutex_wait_proxy_lock() - Wait for lock acquisition
	* @lock: the rt_mutex we were woken on
	* @to: the timeout, null if none. hrtimer should already have
	* been started.
	* @waiter: the pre-initialized rt_mutex_waiter
	*
	* Wait for the lock acquisition started on our behalf by
	* rt_mutex_start_proxy_lock(). Upon failure, the caller must call
	* rt_mutex_cleanup_proxy_lock().
	*
	* Returns:
	* 0 - success
	* <0 - error, one of -EINTR, -ETIMEDOUT
	*
	* Special API call for PI-futex support
	*/
	int __sched rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
	struct hrtimer_sleeper *to,
	struct rt_mutex_waiter *waiter)
	{
	int ret;

	raw_spin_lock_irq(&lock->wait_lock);
	/* sleep on the mutex */
	set_current_state(TASK_INTERRUPTIBLE);
	ret = rt_mutex_slowlock_block(lock, NULL, TASK_INTERRUPTIBLE, to, waiter);
	/*
	* try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
	* have to fix that up.
	*/
	fixup_rt_mutex_waiters(lock);
	raw_spin_unlock_irq(&lock->wait_lock);

	return ret;
	}

	/**
	* rt_mutex_cleanup_proxy_lock() - Cleanup failed lock acquisition
	* @lock: the rt_mutex we were woken on
	* @waiter: the pre-initialized rt_mutex_waiter
	*
	* Attempt to clean up after a failed __rt_mutex_start_proxy_lock() or
	* rt_mutex_wait_proxy_lock().
	*
	* Unless we acquired the lock; we're still enqueued on the wait-list and can
	* in fact still be granted ownership until we're removed. Therefore we can
	* find we are in fact the owner and must disregard the
	* rt_mutex_wait_proxy_lock() failure.
	*
	* Returns:
	* true - did the cleanup, we done.
	* false - we acquired the lock after rt_mutex_wait_proxy_lock() returned,
	* caller should disregards its return value.
	*
	* Special API call for PI-futex support
	*/
	bool __sched rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
	struct rt_mutex_waiter *waiter)
	{
	bool cleanup = false;

	raw_spin_lock_irq(&lock->wait_lock);
	/*
	* Do an unconditional try-lock, this deals with the lock stealing
	* state where __rt_mutex_futex_unlock() -> mark_wakeup_next_waiter()
	* sets a NULL owner.
	*
	* We're not interested in the return value, because the subsequent
	* test on rt_mutex_owner() will infer that. If the trylock succeeded,
	* we will own the lock and it will have removed the waiter. If we
	* failed the trylock, we're still not owner and we need to remove
	* ourselves.
	*/
	try_to_take_rt_mutex(lock, current, waiter);
	/*
	* Unless we're the owner; we're still enqueued on the wait_list.
	* So check if we became owner, if not, take us off the wait_list.
	*/
	if (rt_mutex_owner(lock) != current) {
	remove_waiter(lock, waiter);
	cleanup = true;
	}
	/*
	* try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
	* have to fix that up.
	*/
	fixup_rt_mutex_waiters(lock);

	raw_spin_unlock_irq(&lock->wait_lock);

	return cleanup;
	}

	/*
	* Recheck the pi chain, in case we got a priority setting
	*
	* Called from sched_setscheduler
	*/
	void __sched rt_mutex_adjust_pi(struct task_struct *task)
	{
	struct rt_mutex_waiter *waiter;
	struct rt_mutex_base *next_lock;
	unsigned long flags;

	raw_spin_lock_irqsave(&task->pi_lock, flags);

	waiter = task->pi_blocked_on;
	if (!waiter \|\| rt_mutex_waiter_equal(waiter, task_to_waiter(task))) {
	raw_spin_unlock_irqrestore(&task->pi_lock, flags);
	return;
	}
	next_lock = waiter->lock;
	raw_spin_unlock_irqrestore(&task->pi_lock, flags);

	/* gets dropped in rt_mutex_adjust_prio_chain()! */
	get_task_struct(task);

	rt_mutex_adjust_prio_chain(task, RT_MUTEX_MIN_CHAINWALK, NULL,
	next_lock, NULL, task);
	}

	/*
	* Performs the wakeup of the top-waiter and re-enables preemption.
	*/
	void __sched rt_mutex_postunlock(struct rt_wake_q_head *wqh)
	{
	rt_mutex_wake_up_q(wqh);
	}

	#ifdef CONFIG_DEBUG_RT_MUTEXES
	void rt_mutex_debug_task_free(struct task_struct *task)
	{
	DEBUG_LOCKS_WARN_ON(!RB_EMPTY_ROOT(&task->pi_waiters.rb_root));
	DEBUG_LOCKS_WARN_ON(task->pi_blocked_on);
	}
	#endif

	#ifdef CONFIG_PREEMPT_RT
	/* Mutexes */
	void __mutex_rt_init(struct mutex mutex, const char name,
	struct lock_class_key *key)
	{
	debug_check_no_locks_freed((void )mutex, sizeof(mutex));
	lockdep_init_map_wait(&mutex->dep_map, name, key, 0, LD_WAIT_SLEEP);
	}
	EXPORT_SYMBOL(__mutex_rt_init);

	static __always_inline int __mutex_lock_common(struct mutex *lock,
	unsigned int state,
	unsigned int subclass,
	struct lockdep_map *nest_lock,
	unsigned long ip)
	{
	int ret;

	might_sleep();
	mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
	ret = __rt_mutex_lock(&lock->rtmutex, state);
	if (ret)
	mutex_release(&lock->dep_map, ip);
	else
	lock_acquired(&lock->dep_map, ip);
	return ret;
	}

	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	void __sched mutex_lock_nested(struct mutex *lock, unsigned int subclass)
	{
	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
	}
	EXPORT_SYMBOL_GPL(mutex_lock_nested);

	void __sched _mutex_lock_nest_lock(struct mutex *lock,
	struct lockdep_map *nest_lock)
	{
	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, nest_lock, _RET_IP_);
	}
	EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);

	int __sched mutex_lock_interruptible_nested(struct mutex *lock,
	unsigned int subclass)
	{
	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, subclass, NULL, _RET_IP_);
	}
	EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);

	int __sched mutex_lock_killable_nested(struct mutex *lock,
	unsigned int subclass)
	{
	return __mutex_lock_common(lock, TASK_KILLABLE, subclass, NULL, _RET_IP_);
	}
	EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);

	void __sched mutex_lock_io_nested(struct mutex *lock, unsigned int subclass)
	{
	int token;

	might_sleep();

	token = io_schedule_prepare();
	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
	io_schedule_finish(token);
	}
	EXPORT_SYMBOL_GPL(mutex_lock_io_nested);

	#else /* CONFIG_DEBUG_LOCK_ALLOC */

	void __sched mutex_lock(struct mutex *lock)
	{
	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
	}
	EXPORT_SYMBOL(mutex_lock);

	int __sched mutex_lock_interruptible(struct mutex *lock)
	{
	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_);
	}
	EXPORT_SYMBOL(mutex_lock_interruptible);

	int __sched mutex_lock_killable(struct mutex *lock)
	{
	return __mutex_lock_common(lock, TASK_KILLABLE, 0, NULL, _RET_IP_);
	}
	EXPORT_SYMBOL(mutex_lock_killable);

	void __sched mutex_lock_io(struct mutex *lock)
	{
	int token = io_schedule_prepare();

	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
	io_schedule_finish(token);
	}
	EXPORT_SYMBOL(mutex_lock_io);
	#endif /* !CONFIG_DEBUG_LOCK_ALLOC */

	int __sched mutex_trylock(struct mutex *lock)
	{
	int ret;

	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES) && WARN_ON_ONCE(!in_task()))
	return 0;

	ret = __rt_mutex_trylock(&lock->rtmutex);
	if (ret)
	mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);

	return ret;
	}
	EXPORT_SYMBOL(mutex_trylock);

	void __sched mutex_unlock(struct mutex *lock)
	{
	mutex_release(&lock->dep_map, _RET_IP_);
	__rt_mutex_unlock(&lock->rtmutex);
	}
	EXPORT_SYMBOL(mutex_unlock);

	#endif /* CONFIG_PREEMPT_RT */