text: /* SPDX-License-Identifier: GPL-2.0 */
  /*
   * RT Mutexes: blocking mutual exclusion locks with PI support
   *
   * started by Ingo Molnar and Thomas Gleixner:
   *
   *  Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
   *  Copyright (C) 2006, Timesys Corp., Thomas Gleixner <tglx@timesys.com>
   *
   * This file contains the private data structure and API definitions.
   */
  
  #ifndef __KERNEL_RTMUTEX_COMMON_H
  #define __KERNEL_RTMUTEX_COMMON_H
  
  #include <linux/rtmutex.h>
  #include <linux/sched/wake_q.h>
  
  /*
   * This is the control structure for tasks blocked on a rt_mutex,
   * which is allocated on the kernel stack on of the blocked task.
   *
   * @tree_entry:		pi node to enqueue into the mutex waiters tree
   * @pi_tree_entry:	pi node to enqueue into the mutex owner waiters tree
   * @task:		task reference to the blocked task
   */
  struct rt_mutex_waiter {
  	struct rb_node          tree_entry;
  	struct rb_node          pi_tree_entry;
  	struct task_struct	*task;
  	struct rt_mutex		*lock;
  #ifdef CONFIG_DEBUG_RT_MUTEXES
  	unsigned long		ip;
  	struct pid		*deadlock_task_pid;
  	struct rt_mutex		*deadlock_lock;
  #endif
  	int prio;
  	u64 deadline;
  };
  
  /*
   * Various helpers to access the waiters-tree:
   */
  
  #ifdef CONFIG_RT_MUTEXES
  
  static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
  {
  	return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
  }
  
  static inline struct rt_mutex_waiter *
  rt_mutex_top_waiter(struct rt_mutex *lock)
  {
  	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
  	struct rt_mutex_waiter *w = NULL;
  
  	if (leftmost) {
  		w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
  		BUG_ON(w->lock != lock);
  	}
  	return w;
  }
  
  static inline int task_has_pi_waiters(struct task_struct *p)
  {
  	return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
  }
  
  static inline struct rt_mutex_waiter *
  task_top_pi_waiter(struct task_struct *p)
  {
  	return rb_entry(p->pi_waiters.rb_leftmost,
  			struct rt_mutex_waiter, pi_tree_entry);
  }
  
  #else
  
  static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
  {
  	return false;
  }
  
  static inline struct rt_mutex_waiter *
  rt_mutex_top_waiter(struct rt_mutex *lock)
  {
  	return NULL;
  }
  
  static inline int task_has_pi_waiters(struct task_struct *p)
  {
  	return false;
  }
  
  static inline struct rt_mutex_waiter *
  task_top_pi_waiter(struct task_struct *p)
  {
  	return NULL;
  }
  
  #endif
  
  /*
   * lock->owner state tracking:
   */
  #define RT_MUTEX_HAS_WAITERS	1UL
  
  static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
  {
  	unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
  
  	return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
  }
  
  /*
   * Constants for rt mutex functions which have a selectable deadlock
   * detection.
   *
   * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
   *				no further PI adjustments to be made.
   *
   * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
   *				walk of the lock chain.
   */
  enum rtmutex_chainwalk {
  	RT_MUTEX_MIN_CHAINWALK,
  	RT_MUTEX_FULL_CHAINWALK,
  };
  
  /*
   * PI-futex support (proxy locking functions, etc.):
   */
  extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
  extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
  				       struct task_struct *proxy_owner);
  extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
  				  struct task_struct *proxy_owner);
  extern void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter);
  extern int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
  				     struct rt_mutex_waiter *waiter,
  				     struct task_struct *task);
  extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
  				     struct rt_mutex_waiter *waiter,
  				     struct task_struct *task);
  extern int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
  			       struct hrtimer_sleeper *to,
  			       struct rt_mutex_waiter *waiter);
  extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
  				 struct rt_mutex_waiter *waiter);
  
  extern int rt_mutex_futex_trylock(struct rt_mutex *l);
  extern int __rt_mutex_futex_trylock(struct rt_mutex *l);
  
  extern void rt_mutex_futex_unlock(struct rt_mutex *lock);
  extern bool __rt_mutex_futex_unlock(struct rt_mutex *lock,
  				 struct wake_q_head *wqh);
  
  extern void rt_mutex_postunlock(struct wake_q_head *wake_q);
  
  #ifdef CONFIG_DEBUG_RT_MUTEXES
  # include "rtmutex-debug.h"
  #else
  # include "rtmutex.h"
  #endif
  
  #endif
  