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  * @rtlock_task:	Task pointer for RT lock (spin/rwlock) wakeups
47  */
48 struct rt_wake_q_head {
49 	struct wake_q_head	head;
50 	struct task_struct	*rtlock_task;
51 };
52 
53 #define DEFINE_RT_WAKE_Q(name)						\
54 	struct rt_wake_q_head name = {					\
55 		.head		= WAKE_Q_HEAD_INITIALIZER(name.head),	\
56 		.rtlock_task	= NULL,					\
57 	}
58 
59 /*
60  * PI-futex support (proxy locking functions, etc.):
61  */
62 extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
63 				       struct task_struct *proxy_owner);
64 extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock);
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_start_proxy_lock(struct rt_mutex_base *lock,
69 				     struct rt_mutex_waiter *waiter,
70 				     struct task_struct *task);
71 extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
72 			       struct hrtimer_sleeper *to,
73 			       struct rt_mutex_waiter *waiter);
74 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
75 				 struct rt_mutex_waiter *waiter);
76 
77 extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
78 extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
79 
80 extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
81 extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
82 				struct rt_wake_q_head *wqh);
83 
84 extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh);
85 
86 /*
87  * Must be guarded because this header is included from rcu/tree_plugin.h
88  * unconditionally.
89  */
90 #ifdef CONFIG_RT_MUTEXES
91 static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
92 {
93 	return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
94 }
95 
96 static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
97 {
98 	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
99 	struct rt_mutex_waiter *w = NULL;
100 
101 	if (leftmost) {
102 		w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
103 		BUG_ON(w->lock != lock);
104 	}
105 	return w;
106 }
107 
108 static inline int task_has_pi_waiters(struct task_struct *p)
109 {
110 	return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
111 }
112 
113 static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
114 {
115 	return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
116 			pi_tree_entry);
117 }
118 
119 #define RT_MUTEX_HAS_WAITERS	1UL
120 
121 static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
122 {
123 	unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
124 
125 	return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
126 }
127 
128 /*
129  * Constants for rt mutex functions which have a selectable deadlock
130  * detection.
131  *
132  * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
133  *				no further PI adjustments to be made.
134  *
135  * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
136  *				walk of the lock chain.
137  */
138 enum rtmutex_chainwalk {
139 	RT_MUTEX_MIN_CHAINWALK,
140 	RT_MUTEX_FULL_CHAINWALK,
141 };
142 
143 static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
144 {
145 	raw_spin_lock_init(&lock->wait_lock);
146 	lock->waiters = RB_ROOT_CACHED;
147 	lock->owner = NULL;
148 }
149 
150 /* Debug functions */
151 static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock)
152 {
153 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
154 		DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
155 }
156 
157 static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
158 {
159 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
160 		DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
161 }
162 
163 static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
164 {
165 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
166 		memset(waiter, 0x11, sizeof(*waiter));
167 }
168 
169 static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
170 {
171 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
172 		memset(waiter, 0x22, sizeof(*waiter));
173 }
174 
175 static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
176 {
177 	debug_rt_mutex_init_waiter(waiter);
178 	RB_CLEAR_NODE(&waiter->pi_tree_entry);
179 	RB_CLEAR_NODE(&waiter->tree_entry);
180 	waiter->wake_state = TASK_NORMAL;
181 	waiter->task = NULL;
182 }
183 
184 static inline void rtlock_init_rtmutex_waiter(struct rt_mutex_waiter *waiter)
185 {
186 	rt_mutex_init_waiter(waiter);
187 	waiter->wake_state = TASK_RTLOCK_WAIT;
188 }
189 
190 #else /* CONFIG_RT_MUTEXES */
191 /* Used in rcu/tree_plugin.h */
192 static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
193 {
194 	return NULL;
195 }
196 #endif  /* !CONFIG_RT_MUTEXES */
197 
198 #endif
199