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  * 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  * @prio:		Priority of the waiter
29  * @deadline:		Deadline of the waiter if applicable
30  */
31 struct rt_mutex_waiter {
32 	struct rb_node		tree_entry;
33 	struct rb_node		pi_tree_entry;
34 	struct task_struct	*task;
35 	struct rt_mutex		*lock;
36 	int			prio;
37 	u64			deadline;
38 };
39 
40 /*
41  * Must be guarded because this header is included from rcu/tree_plugin.h
42  * unconditionally.
43  */
44 #ifdef CONFIG_RT_MUTEXES
45 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
46 {
47 	return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
48 }
49 
50 static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex *lock)
51 {
52 	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
53 	struct rt_mutex_waiter *w = NULL;
54 
55 	if (leftmost) {
56 		w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
57 		BUG_ON(w->lock != lock);
58 	}
59 	return w;
60 }
61 
62 static inline int task_has_pi_waiters(struct task_struct *p)
63 {
64 	return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
65 }
66 
67 static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
68 {
69 	return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
70 			pi_tree_entry);
71 }
72 
73 #define RT_MUTEX_HAS_WAITERS	1UL
74 
75 static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
76 {
77 	unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
78 
79 	return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
80 }
81 #else /* CONFIG_RT_MUTEXES */
82 /* Used in rcu/tree_plugin.h */
83 static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
84 {
85 	return NULL;
86 }
87 #endif  /* !CONFIG_RT_MUTEXES */
88 
89 /*
90  * Constants for rt mutex functions which have a selectable deadlock
91  * detection.
92  *
93  * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
94  *				no further PI adjustments to be made.
95  *
96  * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
97  *				walk of the lock chain.
98  */
99 enum rtmutex_chainwalk {
100 	RT_MUTEX_MIN_CHAINWALK,
101 	RT_MUTEX_FULL_CHAINWALK,
102 };
103 
104 static inline void __rt_mutex_basic_init(struct rt_mutex *lock)
105 {
106 	lock->owner = NULL;
107 	raw_spin_lock_init(&lock->wait_lock);
108 	lock->waiters = RB_ROOT_CACHED;
109 }
110 
111 /*
112  * PI-futex support (proxy locking functions, etc.):
113  */
114 extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
115 				       struct task_struct *proxy_owner);
116 extern void rt_mutex_proxy_unlock(struct rt_mutex *lock);
117 extern void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter);
118 extern int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
119 				     struct rt_mutex_waiter *waiter,
120 				     struct task_struct *task);
121 extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
122 				     struct rt_mutex_waiter *waiter,
123 				     struct task_struct *task);
124 extern int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
125 			       struct hrtimer_sleeper *to,
126 			       struct rt_mutex_waiter *waiter);
127 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
128 				 struct rt_mutex_waiter *waiter);
129 
130 extern int rt_mutex_futex_trylock(struct rt_mutex *l);
131 extern int __rt_mutex_futex_trylock(struct rt_mutex *l);
132 
133 extern void rt_mutex_futex_unlock(struct rt_mutex *lock);
134 extern bool __rt_mutex_futex_unlock(struct rt_mutex *lock,
135 				 struct wake_q_head *wqh);
136 
137 extern void rt_mutex_postunlock(struct wake_q_head *wake_q);
138 
139 /* Debug functions */
140 static inline void debug_rt_mutex_unlock(struct rt_mutex *lock)
141 {
142 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
143 		DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
144 }
145 
146 static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
147 {
148 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
149 		DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
150 }
151 
152 static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
153 {
154 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
155 		memset(waiter, 0x11, sizeof(*waiter));
156 }
157 
158 static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
159 {
160 	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
161 		memset(waiter, 0x22, sizeof(*waiter));
162 }
163 
164 #endif
165