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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 <[email protected]>
8 * Copyright (C) 2006, Timesys Corp., Thomas Gleixner <[email protected]>
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)
83 __must_hold(&lock->wait_lock);
84
85extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
86 __must_hold(&lock->wait_lock);
87
88extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
89 struct rt_mutex_waiter *waiter,
90 struct task_struct *task,
91 struct wake_q_head *)
92 __must_hold(&lock->wait_lock);
93
94extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
95 struct rt_mutex_waiter *waiter,
96 struct task_struct *task);
97extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
98 struct hrtimer_sleeper *to,
99 struct rt_mutex_waiter *waiter);
100extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
101 struct rt_mutex_waiter *waiter);
102
103extern int rt_mutex_futex_trylock(struct rt_mutex_base *lock);
104extern int __rt_mutex_futex_trylock(struct rt_mutex_base *lock)
105 __must_hold(&lock->wait_lock);
106
107extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
108extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
109 struct rt_wake_q_head *wqh);
110
111extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh);
112
113/*
114 * Must be guarded because this header is included from rcu/tree_plugin.h
115 * unconditionally.
116 */
117#ifdef CONFIG_RT_MUTEXES
118static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
119 __must_hold(&lock->wait_lock)
120{
121 return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
122}
123
124/*
125 * Lockless speculative check whether @waiter is still the top waiter on
126 * @lock. This is solely comparing pointers and not derefencing the
127 * leftmost entry which might be about to vanish.
128 */
129static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock,
130 struct rt_mutex_waiter *waiter)
131 __must_hold(&lock->wait_lock)
132{
133 struct rb_node *leftmost = rb_first_cached(&lock->waiters);
134
135 return rb_entry(leftmost, struct rt_mutex_waiter, tree.entry) == waiter;
136}
137
138static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
139 __must_hold(&lock->wait_lock)
140{
141 struct rb_node *leftmost = rb_first_cached(&lock->waiters);
142 struct rt_mutex_waiter *w = NULL;
143
144 lockdep_assert_held(&lock->wait_lock);
145
146 if (leftmost) {
147 w = rb_entry(leftmost, struct rt_mutex_waiter, tree.entry);
148 BUG_ON(w->lock != lock);
149 }
150 return w;
151}
152
153static inline int task_has_pi_waiters(struct task_struct *p)
154{
155 return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
156}
157
158static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
159{
160 lockdep_assert_held(&p->pi_lock);
161
162 return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
163 pi_tree.entry);
164}
165
166/*
167 * Constants for rt mutex functions which have a selectable deadlock
168 * detection.
169 *
170 * RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are
171 * no further PI adjustments to be made.
172 *
173 * RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full
174 * walk of the lock chain.
175 */
176enum rtmutex_chainwalk {
177 RT_MUTEX_MIN_CHAINWALK,
178 RT_MUTEX_FULL_CHAINWALK,
179};
180
181static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
182{
183 scoped_guard (raw_spinlock_init, &lock->wait_lock) {
184 lock->waiters = RB_ROOT_CACHED;
185 lock->owner = NULL;
186 }
187}
188
189/* Debug functions */
190static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock)
191{
192 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
193 DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
194}
195
196static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
197{
198 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
199 DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
200}
201
202static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
203{
204 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
205 memset(waiter, 0x11, sizeof(*waiter));
206}
207
208static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
209{
210 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
211 memset(waiter, 0x22, sizeof(*waiter));
212}
213
214static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
215{
216 debug_rt_mutex_init_waiter(waiter);
217 RB_CLEAR_NODE(&waiter->pi_tree.entry);
218 RB_CLEAR_NODE(&waiter->tree.entry);
219 waiter->wake_state = TASK_NORMAL;
220 waiter->task = NULL;
221}
222
223static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter)
224{
225 rt_mutex_init_waiter(waiter);
226 waiter->wake_state = TASK_RTLOCK_WAIT;
227}
228
229#else /* CONFIG_RT_MUTEXES */
230/* Used in rcu/tree_plugin.h */
231static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
232{
233 return NULL;
234}
235#endif /* !CONFIG_RT_MUTEXES */
236
237#endif