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 // 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,
                           struct lockdep_map *nest_lock,
                           unsigned int subclass)
 {
     int ret;
 
     might_sleep();
     mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, _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, NULL, subclass);
 }
 EXPORT_SYMBOL_GPL(rt_mutex_lock_nested);
 
 void __sched _rt_mutex_lock_nest_lock(struct rt_mutex *lock, struct lockdep_map *nest_lock)
 {
     __rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, nest_lock, 0);
 }
 EXPORT_SYMBOL_GPL(_rt_mutex_lock_nest_lock);
 
 #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, NULL, 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, NULL, 0);
 }
 EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
 
 /**
  * rt_mutex_lock_killable - lock a rt_mutex killable
  *
  * @lock:       the rt_mutex to be locked
  *
  * Returns:
  *  0       on success
  * -EINTR   when interrupted by a signal
  */
 int __sched rt_mutex_lock_killable(struct rt_mutex *lock)
 {
     return __rt_mutex_lock_common(lock, TASK_KILLABLE, NULL, 0);
 }
 EXPORT_SYMBOL_GPL(rt_mutex_lock_killable);
 
 /**
  * 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 */

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