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 * 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 */
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,
87 struct wake_q_head *);
88extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
89 struct rt_mutex_waiter *waiter,
90 struct task_struct *task);
91extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
92 struct hrtimer_sleeper *to,
93 struct rt_mutex_waiter *waiter);
94extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
95 struct rt_mutex_waiter *waiter);
96
97extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
98extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
99
100extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
101extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
102 struct rt_wake_q_head *wqh);
103
104extern 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
111static 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 */
121static 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
129static 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
143static inline int task_has_pi_waiters(struct task_struct *p)
144{
145 return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
146}
147
148static 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/*
157 * Constants for rt mutex functions which have a selectable deadlock
158 * detection.
159 *
160 * RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are
161 * no further PI adjustments to be made.
162 *
163 * RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full
164 * walk of the lock chain.
165 */
166enum rtmutex_chainwalk {
167 RT_MUTEX_MIN_CHAINWALK,
168 RT_MUTEX_FULL_CHAINWALK,
169};
170
171static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
172{
173 raw_spin_lock_init(&lock->wait_lock);
174 lock->waiters = RB_ROOT_CACHED;
175 lock->owner = NULL;
176}
177
178/* Debug functions */
179static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock)
180{
181 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
182 DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
183}
184
185static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
186{
187 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
188 DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
189}
190
191static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
192{
193 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
194 memset(s: waiter, c: 0x11, n: sizeof(*waiter));
195}
196
197static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
198{
199 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
200 memset(s: waiter, c: 0x22, n: sizeof(*waiter));
201}
202
203static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
204{
205 debug_rt_mutex_init_waiter(waiter);
206 RB_CLEAR_NODE(&waiter->pi_tree.entry);
207 RB_CLEAR_NODE(&waiter->tree.entry);
208 waiter->wake_state = TASK_NORMAL;
209 waiter->task = NULL;
210}
211
212static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter)
213{
214 rt_mutex_init_waiter(waiter);
215 waiter->wake_state = TASK_RTLOCK_WAIT;
216}
217
218#else /* CONFIG_RT_MUTEXES */
219/* Used in rcu/tree_plugin.h */
220static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
221{
222 return NULL;
223}
224#endif /* !CONFIG_RT_MUTEXES */
225
226#endif
227