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 <[email protected]>
8  *  Copyright (C) 2006, Timesys Corp., Thomas Gleixner <[email protected]>
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  */
32 struct rt_mutex_waiter {
33 	struct rb_node		tree_entry;
34 	struct rb_node		pi_tree_entry;
35 	struct task_struct	*task;
36 	struct rt_mutex_base	*lock;
37 	unsigned int		wake_state;
38 	int			prio;
39 	u64			deadline;
40 };
41 
42 /**
43  * rt_wake_q_head - Wrapper around regular wake_q_head to support
44  *		    "sleeping" spinlocks on RT
45  * @head:	The regular wake_q_head for sleeping lock variants
46  */
47 struct rt_wake_q_head {
48 	struct wake_q_head	head;
49 };
50 
51 #define DEFINE_RT_WAKE_Q(name)						\
52 	struct rt_wake_q_head name = {					\
53 		.head		= WAKE_Q_HEAD_INITIALIZER(name.head),	\
54 	}
55 
56 /*
57  * PI-futex support (proxy locking functions, etc.):
58  */
59 extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
60 				       struct task_struct *proxy_owner);
61 extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock);
62 extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
63 				     struct rt_mutex_waiter *waiter,
64 				     struct task_struct *task);
65 extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
66 				     struct rt_mutex_waiter *waiter,
67 				     struct task_struct *task);
68 extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
69 			       struct hrtimer_sleeper *to,
70 			       struct rt_mutex_waiter *waiter);
71 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
72 				 struct rt_mutex_waiter *waiter);
73 
74 extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
75 extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
76 
77 extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
78 extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
79 				struct wake_q_head *wake_q);
80 
81 extern void rt_mutex_postunlock(struct wake_q_head *wake_q);
82 
83 /*
84  * Must be guarded because this header is included from rcu/tree_plugin.h
85  * unconditionally.
86  */
87 #ifdef CONFIG_RT_MUTEXES
88 static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
89 {
90 	return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
91 }
92 
93 static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
94 {
95 	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
96 	struct rt_mutex_waiter *w = NULL;
97 
98 	if (leftmost) {
99 		w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
100 		BUG_ON(w->lock != lock);
101 	}
102 	return w;
103 }
104 
105 static inline int task_has_pi_waiters(struct task_struct *p)
106 {
107 	return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
108 }
109 
110 static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
111 {
112 	return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
113 			pi_tree_entry);
114 }
115 
116 #define RT_MUTEX_HAS_WAITERS	1UL
117 
118 static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
119 {
120 	unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
121 
122 	return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
123 }
124 
125 /*
126  * Constants for rt mutex functions which have a selectable deadlock
127  * detection.
128  *
129  * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
130  *				no further PI adjustments to be made.
131  *
132  * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
133  *				walk of the lock chain.
134  */
135 enum rtmutex_chainwalk {
136 	RT_MUTEX_MIN_CHAINWALK,
137 	RT_MUTEX_FULL_CHAINWALK,
138 };
139 
140 static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
141 {
142 	raw_spin_lock_init(&lock->wait_lock);
143 	lock->waiters = RB_ROOT_CACHED;
144 	lock->owner = NULL;
145 }
146 
147 /* Debug functions */
148 static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock)
149 {
150 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
151 		DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
152 }
153 
154 static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
155 {
156 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
157 		DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
158 }
159 
160 static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
161 {
162 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
163 		memset(waiter, 0x11, sizeof(*waiter));
164 }
165 
166 static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
167 {
168 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
169 		memset(waiter, 0x22, sizeof(*waiter));
170 }
171 
172 static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
173 {
174 	debug_rt_mutex_init_waiter(waiter);
175 	RB_CLEAR_NODE(&waiter->pi_tree_entry);
176 	RB_CLEAR_NODE(&waiter->tree_entry);
177 	waiter->wake_state = TASK_NORMAL;
178 	waiter->task = NULL;
179 }
180 
181 static inline void rtlock_init_rtmutex_waiter(struct rt_mutex_waiter *waiter)
182 {
183 	rt_mutex_init_waiter(waiter);
184 	waiter->wake_state = TASK_RTLOCK_WAIT;
185 }
186 
187 #else /* CONFIG_RT_MUTEXES */
188 /* Used in rcu/tree_plugin.h */
189 static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
190 {
191 	return NULL;
192 }
193 #endif  /* !CONFIG_RT_MUTEXES */
194 
195 #endif
196