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 | |