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 */
32 struct 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 */
52 struct 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 */
67 struct 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 */
81 extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
82 struct task_struct *proxy_owner);
83 extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock);
84 extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
85 struct rt_mutex_waiter *waiter,
86 struct task_struct *task);
87 extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
88 struct rt_mutex_waiter *waiter,
89 struct task_struct *task);
90 extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
91 struct hrtimer_sleeper *to,
92 struct rt_mutex_waiter *waiter);
93 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
94 struct rt_mutex_waiter *waiter);
95
96 extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
97 extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
98
99 extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
100 extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
101 struct rt_wake_q_head *wqh);
102
103 extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh);
104
105 /*
106 * Must be guarded because this header is included from rcu/tree_plugin.h
107 * unconditionally.
108 */
109 #ifdef CONFIG_RT_MUTEXES
110 static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
111 {
112 return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
113 }
114
115 /*
116 * Lockless speculative check whether @waiter is still the top waiter on
117 * @lock. This is solely comparing pointers and not derefencing the
118 * leftmost entry which might be about to vanish.
119 */
120 static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock,
121 struct rt_mutex_waiter *waiter)
122 {
123 struct rb_node *leftmost = rb_first_cached(&lock->waiters);
124
125 return rb_entry(leftmost, struct rt_mutex_waiter, tree.entry) == waiter;
126 }
127
128 static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
129 {
130 struct rb_node *leftmost = rb_first_cached(&lock->waiters);
131 struct rt_mutex_waiter *w = NULL;
132
133 lockdep_assert_held(&lock->wait_lock);
134
135 if (leftmost) {
136 w = rb_entry(leftmost, struct rt_mutex_waiter, tree.entry);
137 BUG_ON(w->lock != lock);
138 }
139 return w;
140 }
141
142 static inline int task_has_pi_waiters(struct task_struct *p)
143 {
144 return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
145 }
146
147 static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
148 {
149 lockdep_assert_held(&p->pi_lock);
150
151 return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
152 pi_tree.entry);
153 }
154
155 #define RT_MUTEX_HAS_WAITERS 1UL
156
157 static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
158 {
159 unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
160
161 return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
162 }
163
164 /*
165 * Constants for rt mutex functions which have a selectable deadlock
166 * detection.
167 *
168 * RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are
169 * no further PI adjustments to be made.
170 *
171 * RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full
172 * walk of the lock chain.
173 */
174 enum rtmutex_chainwalk {
175 RT_MUTEX_MIN_CHAINWALK,
176 RT_MUTEX_FULL_CHAINWALK,
177 };
178
179 static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
180 {
181 raw_spin_lock_init(&lock->wait_lock);
182 lock->waiters = RB_ROOT_CACHED;
183 lock->owner = NULL;
184 }
185
186 /* Debug functions */
187 static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock)
188 {
189 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
190 DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
191 }
192
193 static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
194 {
195 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
196 DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
197 }
198
199 static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
200 {
201 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
202 memset(waiter, 0x11, sizeof(*waiter));
203 }
204
205 static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
206 {
207 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
208 memset(waiter, 0x22, sizeof(*waiter));
209 }
210
211 static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
212 {
213 debug_rt_mutex_init_waiter(waiter);
214 RB_CLEAR_NODE(&waiter->pi_tree.entry);
215 RB_CLEAR_NODE(&waiter->tree.entry);
216 waiter->wake_state = TASK_NORMAL;
217 waiter->task = NULL;
218 }
219
220 static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter)
221 {
222 rt_mutex_init_waiter(waiter);
223 waiter->wake_state = TASK_RTLOCK_WAIT;
224 }
225
226 #else /* CONFIG_RT_MUTEXES */
227 /* Used in rcu/tree_plugin.h */
228 static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
229 {
230 return NULL;
231 }
232 #endif /* !CONFIG_RT_MUTEXES */
233
234 #endif
235
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.