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 */
32struct 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 */
52struct 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 * 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 */
67struct 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 */
81extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
82				       struct task_struct *proxy_owner);
83extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock);
84extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
85				     struct rt_mutex_waiter *waiter,
86				     struct task_struct *task);
87extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
88				     struct rt_mutex_waiter *waiter,
89				     struct task_struct *task);
90extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
91			       struct hrtimer_sleeper *to,
92			       struct rt_mutex_waiter *waiter);
93extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
94				 struct rt_mutex_waiter *waiter);
95
96extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
97extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
98
99extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
100extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
101				struct rt_wake_q_head *wqh);
102
103extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh);
104
105/*
106 * Must be guarded because this header is included from rcu/tree_plugin.h
107 * unconditionally.
108 */
109#ifdef CONFIG_RT_MUTEXES
110static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
111{
112	return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
113}
114
115/*
116 * Lockless speculative check whether @waiter is still the top waiter on
117 * @lock. This is solely comparing pointers and not derefencing the
118 * leftmost entry which might be about to vanish.
119 */
120static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock,
121						 struct rt_mutex_waiter *waiter)
122{
123	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
124
125	return rb_entry(leftmost, struct rt_mutex_waiter, tree.entry) == waiter;
126}
127
128static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
129{
130	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
131	struct rt_mutex_waiter *w = NULL;
132
133	lockdep_assert_held(&lock->wait_lock);
134
135	if (leftmost) {
136		w = rb_entry(leftmost, struct rt_mutex_waiter, tree.entry);
137		BUG_ON(w->lock != lock);
138	}
139	return w;
140}
141
142static inline int task_has_pi_waiters(struct task_struct *p)
143{
144	return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
145}
146
147static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
148{
149	lockdep_assert_held(&p->pi_lock);
150
151	return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
152			pi_tree.entry);
153}
154
155#define RT_MUTEX_HAS_WAITERS	1UL
156
157static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
158{
159	unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
160
161	return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
162}
163
164/*
165 * Constants for rt mutex functions which have a selectable deadlock
166 * detection.
167 *
168 * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
169 *				no further PI adjustments to be made.
170 *
171 * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
172 *				walk of the lock chain.
173 */
174enum rtmutex_chainwalk {
175	RT_MUTEX_MIN_CHAINWALK,
176	RT_MUTEX_FULL_CHAINWALK,
177};
178
179static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
180{
181	raw_spin_lock_init(&lock->wait_lock);
182	lock->waiters = RB_ROOT_CACHED;
183	lock->owner = NULL;
184}
185
186/* Debug functions */
187static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock)
188{
189	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
190		DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
191}
192
193static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
194{
195	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
196		DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
197}
198
199static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
200{
201	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
202		memset(waiter, 0x11, sizeof(*waiter));
203}
204
205static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
206{
207	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
208		memset(waiter, 0x22, sizeof(*waiter));
209}
210
211static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
212{
213	debug_rt_mutex_init_waiter(waiter);
214	RB_CLEAR_NODE(&waiter->pi_tree.entry);
215	RB_CLEAR_NODE(&waiter->tree.entry);
216	waiter->wake_state = TASK_NORMAL;
217	waiter->task = NULL;
218}
219
220static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter)
221{
222	rt_mutex_init_waiter(waiter);
223	waiter->wake_state = TASK_RTLOCK_WAIT;
224}
225
226#else /* CONFIG_RT_MUTEXES */
227/* Used in rcu/tree_plugin.h */
228static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
229{
230	return NULL;
231}
232#endif  /* !CONFIG_RT_MUTEXES */
233
234#endif
235