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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/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,
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#define RT_MUTEX_HAS_WAITERS 1UL
157
158static 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 */
175enum rtmutex_chainwalk {
176 RT_MUTEX_MIN_CHAINWALK,
177 RT_MUTEX_FULL_CHAINWALK,
178};
179
180static 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 */
188static 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
194static 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
200static 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
206static 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
212static 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
221static 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 */
229static 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
1/*
2 * RT Mutexes: blocking mutual exclusion locks with PI support
3 *
4 * started by Ingo Molnar and Thomas Gleixner:
5 *
6 * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
7 * Copyright (C) 2006, Timesys Corp., Thomas Gleixner <tglx@timesys.com>
8 *
9 * This file contains the private data structure and API definitions.
10 */
11
12#ifndef __KERNEL_RTMUTEX_COMMON_H
13#define __KERNEL_RTMUTEX_COMMON_H
14
15#include <linux/rtmutex.h>
16
17/*
18 * The rtmutex in kernel tester is independent of rtmutex debugging. We
19 * call schedule_rt_mutex_test() instead of schedule() for the tasks which
20 * belong to the tester. That way we can delay the wakeup path of those
21 * threads to provoke lock stealing and testing of complex boosting scenarios.
22 */
23#ifdef CONFIG_RT_MUTEX_TESTER
24
25extern void schedule_rt_mutex_test(struct rt_mutex *lock);
26
27#define schedule_rt_mutex(_lock) \
28 do { \
29 if (!(current->flags & PF_MUTEX_TESTER)) \
30 schedule(); \
31 else \
32 schedule_rt_mutex_test(_lock); \
33 } while (0)
34
35#else
36# define schedule_rt_mutex(_lock) schedule()
37#endif
38
39/*
40 * This is the control structure for tasks blocked on a rt_mutex,
41 * which is allocated on the kernel stack on of the blocked task.
42 *
43 * @tree_entry: pi node to enqueue into the mutex waiters tree
44 * @pi_tree_entry: pi node to enqueue into the mutex owner waiters tree
45 * @task: task reference to the blocked task
46 */
47struct rt_mutex_waiter {
48 struct rb_node tree_entry;
49 struct rb_node pi_tree_entry;
50 struct task_struct *task;
51 struct rt_mutex *lock;
52#ifdef CONFIG_DEBUG_RT_MUTEXES
53 unsigned long ip;
54 struct pid *deadlock_task_pid;
55 struct rt_mutex *deadlock_lock;
56#endif
57 int prio;
58};
59
60/*
61 * Various helpers to access the waiters-tree:
62 */
63static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
64{
65 return !RB_EMPTY_ROOT(&lock->waiters);
66}
67
68static inline struct rt_mutex_waiter *
69rt_mutex_top_waiter(struct rt_mutex *lock)
70{
71 struct rt_mutex_waiter *w;
72
73 w = rb_entry(lock->waiters_leftmost, struct rt_mutex_waiter,
74 tree_entry);
75 BUG_ON(w->lock != lock);
76
77 return w;
78}
79
80static inline int task_has_pi_waiters(struct task_struct *p)
81{
82 return !RB_EMPTY_ROOT(&p->pi_waiters);
83}
84
85static inline struct rt_mutex_waiter *
86task_top_pi_waiter(struct task_struct *p)
87{
88 return rb_entry(p->pi_waiters_leftmost, struct rt_mutex_waiter,
89 pi_tree_entry);
90}
91
92/*
93 * lock->owner state tracking:
94 */
95#define RT_MUTEX_HAS_WAITERS 1UL
96#define RT_MUTEX_OWNER_MASKALL 1UL
97
98static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
99{
100 return (struct task_struct *)
101 ((unsigned long)lock->owner & ~RT_MUTEX_OWNER_MASKALL);
102}
103
104/*
105 * PI-futex support (proxy locking functions, etc.):
106 */
107extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
108extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
109 struct task_struct *proxy_owner);
110extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
111 struct task_struct *proxy_owner);
112extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
113 struct rt_mutex_waiter *waiter,
114 struct task_struct *task,
115 int detect_deadlock);
116extern int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
117 struct hrtimer_sleeper *to,
118 struct rt_mutex_waiter *waiter,
119 int detect_deadlock);
120
121#ifdef CONFIG_DEBUG_RT_MUTEXES
122# include "rtmutex-debug.h"
123#else
124# include "rtmutex.h"
125#endif
126
127#endif