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 */
33 struct 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 */
50 struct 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 */
64 extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
65 struct task_struct *proxy_owner);
66 extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock);
67 extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
68 struct rt_mutex_waiter *waiter,
69 struct task_struct *task);
70 extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
71 struct rt_mutex_waiter *waiter,
72 struct task_struct *task);
73 extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
74 struct hrtimer_sleeper *to,
75 struct rt_mutex_waiter *waiter);
76 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
77 struct rt_mutex_waiter *waiter);
78
79 extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
80 extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
81
82 extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
83 extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
84 struct rt_wake_q_head *wqh);
85
86 extern 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
rt_mutex_has_waiters(struct rt_mutex_base * lock)93 static 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 */
rt_mutex_waiter_is_top_waiter(struct rt_mutex_base * lock,struct rt_mutex_waiter * waiter)103 static 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
rt_mutex_top_waiter(struct rt_mutex_base * lock)111 static 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
task_has_pi_waiters(struct task_struct * p)123 static inline int task_has_pi_waiters(struct task_struct *p)
124 {
125 return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
126 }
127
task_top_pi_waiter(struct task_struct * p)128 static 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
rt_mutex_owner(struct rt_mutex_base * lock)136 static 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 */
153 enum rtmutex_chainwalk {
154 RT_MUTEX_MIN_CHAINWALK,
155 RT_MUTEX_FULL_CHAINWALK,
156 };
157
__rt_mutex_base_init(struct rt_mutex_base * lock)158 static 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 */
debug_rt_mutex_unlock(struct rt_mutex_base * lock)166 static 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
debug_rt_mutex_proxy_unlock(struct rt_mutex_base * lock)172 static 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
debug_rt_mutex_init_waiter(struct rt_mutex_waiter * waiter)178 static 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
debug_rt_mutex_free_waiter(struct rt_mutex_waiter * waiter)184 static 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
rt_mutex_init_waiter(struct rt_mutex_waiter * waiter)190 static 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
rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter * waiter)199 static 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 */
rt_mutex_owner(struct rt_mutex_base * lock)207 static 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
214