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