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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 <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/rtmutex.h>
17#include <linux/sched/wake_q.h>
18
19/*
20 * This is the control structure for tasks blocked on a rt_mutex,
21 * which is allocated on the kernel stack on of the blocked task.
22 *
23 * @tree_entry: pi node to enqueue into the mutex waiters tree
24 * @pi_tree_entry: pi node to enqueue into the mutex owner waiters tree
25 * @task: task reference to the blocked task
26 */
27struct rt_mutex_waiter {
28 struct rb_node tree_entry;
29 struct rb_node pi_tree_entry;
30 struct task_struct *task;
31 struct rt_mutex *lock;
32#ifdef CONFIG_DEBUG_RT_MUTEXES
33 unsigned long ip;
34 struct pid *deadlock_task_pid;
35 struct rt_mutex *deadlock_lock;
36#endif
37 int prio;
38 u64 deadline;
39};
40
41/*
42 * Various helpers to access the waiters-tree:
43 */
44
45#ifdef CONFIG_RT_MUTEXES
46
47static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
48{
49 return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
50}
51
52static inline struct rt_mutex_waiter *
53rt_mutex_top_waiter(struct rt_mutex *lock)
54{
55 struct rb_node *leftmost = rb_first_cached(&lock->waiters);
56 struct rt_mutex_waiter *w = NULL;
57
58 if (leftmost) {
59 w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
60 BUG_ON(w->lock != lock);
61 }
62 return w;
63}
64
65static inline int task_has_pi_waiters(struct task_struct *p)
66{
67 return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
68}
69
70static inline struct rt_mutex_waiter *
71task_top_pi_waiter(struct task_struct *p)
72{
73 return rb_entry(p->pi_waiters.rb_leftmost,
74 struct rt_mutex_waiter, pi_tree_entry);
75}
76
77#else
78
79static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
80{
81 return false;
82}
83
84static inline struct rt_mutex_waiter *
85rt_mutex_top_waiter(struct rt_mutex *lock)
86{
87 return NULL;
88}
89
90static inline int task_has_pi_waiters(struct task_struct *p)
91{
92 return false;
93}
94
95static inline struct rt_mutex_waiter *
96task_top_pi_waiter(struct task_struct *p)
97{
98 return NULL;
99}
100
101#endif
102
103/*
104 * lock->owner state tracking:
105 */
106#define RT_MUTEX_HAS_WAITERS 1UL
107
108static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
109{
110 unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
111
112 return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
113}
114
115/*
116 * Constants for rt mutex functions which have a selectable deadlock
117 * detection.
118 *
119 * RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are
120 * no further PI adjustments to be made.
121 *
122 * RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full
123 * walk of the lock chain.
124 */
125enum rtmutex_chainwalk {
126 RT_MUTEX_MIN_CHAINWALK,
127 RT_MUTEX_FULL_CHAINWALK,
128};
129
130/*
131 * PI-futex support (proxy locking functions, etc.):
132 */
133extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
134extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
135 struct task_struct *proxy_owner);
136extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
137 struct task_struct *proxy_owner);
138extern void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter);
139extern int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
140 struct rt_mutex_waiter *waiter,
141 struct task_struct *task);
142extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
143 struct rt_mutex_waiter *waiter,
144 struct task_struct *task);
145extern int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
146 struct hrtimer_sleeper *to,
147 struct rt_mutex_waiter *waiter);
148extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
149 struct rt_mutex_waiter *waiter);
150
151extern int rt_mutex_futex_trylock(struct rt_mutex *l);
152extern int __rt_mutex_futex_trylock(struct rt_mutex *l);
153
154extern void rt_mutex_futex_unlock(struct rt_mutex *lock);
155extern bool __rt_mutex_futex_unlock(struct rt_mutex *lock,
156 struct wake_q_head *wqh);
157
158extern void rt_mutex_postunlock(struct wake_q_head *wake_q);
159
160#ifdef CONFIG_DEBUG_RT_MUTEXES
161# include "rtmutex-debug.h"
162#else
163# include "rtmutex.h"
164#endif
165
166#endif
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 * This is the control structure for tasks blocked on a rt_mutex,
22 * which is allocated on the kernel stack on of the blocked task.
23 *
24 * @tree_entry: pi node to enqueue into the mutex waiters tree
25 * @pi_tree_entry: pi node to enqueue into the mutex owner waiters tree
26 * @task: task reference to the blocked task
27 * @lock: Pointer to the rt_mutex on which the waiter blocks
28 * @wake_state: Wakeup state to use (TASK_NORMAL or TASK_RTLOCK_WAIT)
29 * @prio: Priority of the waiter
30 * @deadline: Deadline of the waiter if applicable
31 * @ww_ctx: WW context pointer
32 */
33struct rt_mutex_waiter {
34 struct rb_node tree_entry;
35 struct rb_node pi_tree_entry;
36 struct task_struct *task;
37 struct rt_mutex_base *lock;
38 unsigned int wake_state;
39 int prio;
40 u64 deadline;
41 struct ww_acquire_ctx *ww_ctx;
42};
43
44/**
45 * rt_wake_q_head - Wrapper around regular wake_q_head to support
46 * "sleeping" spinlocks on RT
47 * @head: The regular wake_q_head for sleeping lock variants
48 * @rtlock_task: Task pointer for RT lock (spin/rwlock) wakeups
49 */
50struct rt_wake_q_head {
51 struct wake_q_head head;
52 struct task_struct *rtlock_task;
53};
54
55#define DEFINE_RT_WAKE_Q(name) \
56 struct rt_wake_q_head name = { \
57 .head = WAKE_Q_HEAD_INITIALIZER(name.head), \
58 .rtlock_task = NULL, \
59 }
60
61/*
62 * PI-futex support (proxy locking functions, etc.):
63 */
64extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
65 struct task_struct *proxy_owner);
66extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock);
67extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
68 struct rt_mutex_waiter *waiter,
69 struct task_struct *task);
70extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
71 struct rt_mutex_waiter *waiter,
72 struct task_struct *task);
73extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
74 struct hrtimer_sleeper *to,
75 struct rt_mutex_waiter *waiter);
76extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
77 struct rt_mutex_waiter *waiter);
78
79extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
80extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
81
82extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
83extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
84 struct rt_wake_q_head *wqh);
85
86extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh);
87
88/*
89 * Must be guarded because this header is included from rcu/tree_plugin.h
90 * unconditionally.
91 */
92#ifdef CONFIG_RT_MUTEXES
93static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
94{
95 return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
96}
97
98/*
99 * Lockless speculative check whether @waiter is still the top waiter on
100 * @lock. This is solely comparing pointers and not derefencing the
101 * leftmost entry which might be about to vanish.
102 */
103static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock,
104 struct rt_mutex_waiter *waiter)
105{
106 struct rb_node *leftmost = rb_first_cached(&lock->waiters);
107
108 return rb_entry(leftmost, struct rt_mutex_waiter, tree_entry) == waiter;
109}
110
111static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
112{
113 struct rb_node *leftmost = rb_first_cached(&lock->waiters);
114 struct rt_mutex_waiter *w = NULL;
115
116 if (leftmost) {
117 w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
118 BUG_ON(w->lock != lock);
119 }
120 return w;
121}
122
123static inline int task_has_pi_waiters(struct task_struct *p)
124{
125 return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
126}
127
128static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
129{
130 return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
131 pi_tree_entry);
132}
133
134#define RT_MUTEX_HAS_WAITERS 1UL
135
136static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
137{
138 unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
139
140 return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
141}
142
143/*
144 * Constants for rt mutex functions which have a selectable deadlock
145 * detection.
146 *
147 * RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are
148 * no further PI adjustments to be made.
149 *
150 * RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full
151 * walk of the lock chain.
152 */
153enum rtmutex_chainwalk {
154 RT_MUTEX_MIN_CHAINWALK,
155 RT_MUTEX_FULL_CHAINWALK,
156};
157
158static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
159{
160 raw_spin_lock_init(&lock->wait_lock);
161 lock->waiters = RB_ROOT_CACHED;
162 lock->owner = NULL;
163}
164
165/* Debug functions */
166static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock)
167{
168 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
169 DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
170}
171
172static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
173{
174 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
175 DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
176}
177
178static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
179{
180 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
181 memset(waiter, 0x11, sizeof(*waiter));
182}
183
184static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
185{
186 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
187 memset(waiter, 0x22, sizeof(*waiter));
188}
189
190static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
191{
192 debug_rt_mutex_init_waiter(waiter);
193 RB_CLEAR_NODE(&waiter->pi_tree_entry);
194 RB_CLEAR_NODE(&waiter->tree_entry);
195 waiter->wake_state = TASK_NORMAL;
196 waiter->task = NULL;
197}
198
199static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter)
200{
201 rt_mutex_init_waiter(waiter);
202 waiter->wake_state = TASK_RTLOCK_WAIT;
203}
204
205#else /* CONFIG_RT_MUTEXES */
206/* Used in rcu/tree_plugin.h */
207static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
208{
209 return NULL;
210}
211#endif /* !CONFIG_RT_MUTEXES */
212
213#endif