xref: /linux/kernel/locking/rtmutex_common.h (revision f4915933947c71f08ed1c5a6c9b4fdbe735e18cf)
1  /* SPDX-License-Identifier: GPL-2.0 */
2  /*
3   * RT Mutexes: blocking mutual exclusion locks with PI support
4   *
5   * started by Ingo Molnar and Thomas Gleixner:
6   *
7   *  Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
8   *  Copyright (C) 2006, Timesys Corp., Thomas Gleixner <tglx@timesys.com>
9   *
10   * This file contains the private data structure and API definitions.
11   */
12  
13  #ifndef __KERNEL_RTMUTEX_COMMON_H
14  #define __KERNEL_RTMUTEX_COMMON_H
15  
16  #include <linux/debug_locks.h>
17  #include <linux/rtmutex.h>
18  #include <linux/sched/wake_q.h>
19  
20  
21  /*
22   * This is a helper for the struct rt_mutex_waiter below. A waiter goes in two
23   * separate trees and they need their own copy of the sort keys because of
24   * different locking requirements.
25   *
26   * @entry:		rbtree node to enqueue into the waiters tree
27   * @prio:		Priority of the waiter
28   * @deadline:		Deadline of the waiter if applicable
29   *
30   * See rt_waiter_node_less() and waiter_*_prio().
31   */
32  struct rt_waiter_node {
33  	struct rb_node	entry;
34  	int		prio;
35  	u64		deadline;
36  };
37  
38  /*
39   * This is the control structure for tasks blocked on a rt_mutex,
40   * which is allocated on the kernel stack on of the blocked task.
41   *
42   * @tree:		node to enqueue into the mutex waiters tree
43   * @pi_tree:		node to enqueue into the mutex owner waiters tree
44   * @task:		task reference to the blocked task
45   * @lock:		Pointer to the rt_mutex on which the waiter blocks
46   * @wake_state:		Wakeup state to use (TASK_NORMAL or TASK_RTLOCK_WAIT)
47   * @ww_ctx:		WW context pointer
48   *
49   * @tree is ordered by @lock->wait_lock
50   * @pi_tree is ordered by rt_mutex_owner(@lock)->pi_lock
51   */
52  struct rt_mutex_waiter {
53  	struct rt_waiter_node	tree;
54  	struct rt_waiter_node	pi_tree;
55  	struct task_struct	*task;
56  	struct rt_mutex_base	*lock;
57  	unsigned int		wake_state;
58  	struct ww_acquire_ctx	*ww_ctx;
59  };
60  
61  /**
62   * struct rt_wake_q_head - Wrapper around regular wake_q_head to support
63   *			   "sleeping" spinlocks on RT
64   * @head:		The regular wake_q_head for sleeping lock variants
65   * @rtlock_task:	Task pointer for RT lock (spin/rwlock) wakeups
66   */
67  struct rt_wake_q_head {
68  	struct wake_q_head	head;
69  	struct task_struct	*rtlock_task;
70  };
71  
72  #define DEFINE_RT_WAKE_Q(name)						\
73  	struct rt_wake_q_head name = {					\
74  		.head		= WAKE_Q_HEAD_INITIALIZER(name.head),	\
75  		.rtlock_task	= NULL,					\
76  	}
77  
78  /*
79   * PI-futex support (proxy locking functions, etc.):
80   */
81  extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
82  				       struct task_struct *proxy_owner);
83  extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock);
84  extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
85  				     struct rt_mutex_waiter *waiter,
86  				     struct task_struct *task,
87  				     struct wake_q_head *);
88  extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
89  				     struct rt_mutex_waiter *waiter,
90  				     struct task_struct *task);
91  extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
92  			       struct hrtimer_sleeper *to,
93  			       struct rt_mutex_waiter *waiter);
94  extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
95  				 struct rt_mutex_waiter *waiter);
96  
97  extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
98  extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
99  
100  extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
101  extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
102  				struct rt_wake_q_head *wqh);
103  
104  extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh);
105  
106  /*
107   * Must be guarded because this header is included from rcu/tree_plugin.h
108   * unconditionally.
109   */
110  #ifdef CONFIG_RT_MUTEXES
rt_mutex_has_waiters(struct rt_mutex_base * lock)111  static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
112  {
113  	return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
114  }
115  
116  /*
117   * Lockless speculative check whether @waiter is still the top waiter on
118   * @lock. This is solely comparing pointers and not derefencing the
119   * leftmost entry which might be about to vanish.
120   */
rt_mutex_waiter_is_top_waiter(struct rt_mutex_base * lock,struct rt_mutex_waiter * waiter)121  static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock,
122  						 struct rt_mutex_waiter *waiter)
123  {
124  	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
125  
126  	return rb_entry(leftmost, struct rt_mutex_waiter, tree.entry) == waiter;
127  }
128  
rt_mutex_top_waiter(struct rt_mutex_base * lock)129  static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
130  {
131  	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
132  	struct rt_mutex_waiter *w = NULL;
133  
134  	lockdep_assert_held(&lock->wait_lock);
135  
136  	if (leftmost) {
137  		w = rb_entry(leftmost, struct rt_mutex_waiter, tree.entry);
138  		BUG_ON(w->lock != lock);
139  	}
140  	return w;
141  }
142  
task_has_pi_waiters(struct task_struct * p)143  static inline int task_has_pi_waiters(struct task_struct *p)
144  {
145  	return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
146  }
147  
task_top_pi_waiter(struct task_struct * p)148  static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
149  {
150  	lockdep_assert_held(&p->pi_lock);
151  
152  	return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
153  			pi_tree.entry);
154  }
155  
156  #define RT_MUTEX_HAS_WAITERS	1UL
157  
rt_mutex_owner(struct rt_mutex_base * lock)158  static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
159  {
160  	unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
161  
162  	return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
163  }
164  
165  /*
166   * Constants for rt mutex functions which have a selectable deadlock
167   * detection.
168   *
169   * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
170   *				no further PI adjustments to be made.
171   *
172   * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
173   *				walk of the lock chain.
174   */
175  enum rtmutex_chainwalk {
176  	RT_MUTEX_MIN_CHAINWALK,
177  	RT_MUTEX_FULL_CHAINWALK,
178  };
179  
__rt_mutex_base_init(struct rt_mutex_base * lock)180  static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
181  {
182  	raw_spin_lock_init(&lock->wait_lock);
183  	lock->waiters = RB_ROOT_CACHED;
184  	lock->owner = NULL;
185  }
186  
187  /* Debug functions */
debug_rt_mutex_unlock(struct rt_mutex_base * lock)188  static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock)
189  {
190  	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
191  		DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
192  }
193  
debug_rt_mutex_proxy_unlock(struct rt_mutex_base * lock)194  static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
195  {
196  	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
197  		DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
198  }
199  
debug_rt_mutex_init_waiter(struct rt_mutex_waiter * waiter)200  static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
201  {
202  	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
203  		memset(waiter, 0x11, sizeof(*waiter));
204  }
205  
debug_rt_mutex_free_waiter(struct rt_mutex_waiter * waiter)206  static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
207  {
208  	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
209  		memset(waiter, 0x22, sizeof(*waiter));
210  }
211  
rt_mutex_init_waiter(struct rt_mutex_waiter * waiter)212  static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
213  {
214  	debug_rt_mutex_init_waiter(waiter);
215  	RB_CLEAR_NODE(&waiter->pi_tree.entry);
216  	RB_CLEAR_NODE(&waiter->tree.entry);
217  	waiter->wake_state = TASK_NORMAL;
218  	waiter->task = NULL;
219  }
220  
rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter * waiter)221  static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter)
222  {
223  	rt_mutex_init_waiter(waiter);
224  	waiter->wake_state = TASK_RTLOCK_WAIT;
225  }
226  
227  #else /* CONFIG_RT_MUTEXES */
228  /* Used in rcu/tree_plugin.h */
rt_mutex_owner(struct rt_mutex_base * lock)229  static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
230  {
231  	return NULL;
232  }
233  #endif  /* !CONFIG_RT_MUTEXES */
234  
235  #endif
236