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/rtmutex.h>
17 #include <linux/sched/wake_q.h>
18 
19 /*
20  * This is the control structure for tasks blocked on a rt_mutex,
21  * which is allocated on the kernel stack on of the blocked task.
22  *
23  * @tree_entry:		pi node to enqueue into the mutex waiters tree
24  * @pi_tree_entry:	pi node to enqueue into the mutex owner waiters tree
25  * @task:		task reference to the blocked task
26  */
27 struct rt_mutex_waiter {
28 	struct rb_node          tree_entry;
29 	struct rb_node          pi_tree_entry;
30 	struct task_struct	*task;
31 	struct rt_mutex		*lock;
32 	int prio;
33 	u64 deadline;
34 };
35 
36 /*
37  * Various helpers to access the waiters-tree:
38  */
39 
40 #ifdef CONFIG_RT_MUTEXES
41 
42 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
43 {
44 	return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
45 }
46 
47 static inline struct rt_mutex_waiter *
48 rt_mutex_top_waiter(struct rt_mutex *lock)
49 {
50 	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
51 	struct rt_mutex_waiter *w = NULL;
52 
53 	if (leftmost) {
54 		w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
55 		BUG_ON(w->lock != lock);
56 	}
57 	return w;
58 }
59 
60 static inline int task_has_pi_waiters(struct task_struct *p)
61 {
62 	return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
63 }
64 
65 static inline struct rt_mutex_waiter *
66 task_top_pi_waiter(struct task_struct *p)
67 {
68 	return rb_entry(p->pi_waiters.rb_leftmost,
69 			struct rt_mutex_waiter, pi_tree_entry);
70 }
71 
72 #else
73 
74 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
75 {
76 	return false;
77 }
78 
79 static inline struct rt_mutex_waiter *
80 rt_mutex_top_waiter(struct rt_mutex *lock)
81 {
82 	return NULL;
83 }
84 
85 static inline int task_has_pi_waiters(struct task_struct *p)
86 {
87 	return false;
88 }
89 
90 static inline struct rt_mutex_waiter *
91 task_top_pi_waiter(struct task_struct *p)
92 {
93 	return NULL;
94 }
95 
96 #endif
97 
98 /*
99  * lock->owner state tracking:
100  */
101 #define RT_MUTEX_HAS_WAITERS	1UL
102 
103 static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
104 {
105 	unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
106 
107 	return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
108 }
109 
110 /*
111  * Constants for rt mutex functions which have a selectable deadlock
112  * detection.
113  *
114  * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
115  *				no further PI adjustments to be made.
116  *
117  * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
118  *				walk of the lock chain.
119  */
120 enum rtmutex_chainwalk {
121 	RT_MUTEX_MIN_CHAINWALK,
122 	RT_MUTEX_FULL_CHAINWALK,
123 };
124 
125 /*
126  * PI-futex support (proxy locking functions, etc.):
127  */
128 extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
129 				       struct task_struct *proxy_owner);
130 extern void rt_mutex_proxy_unlock(struct rt_mutex *lock);
131 extern void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter);
132 extern int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
133 				     struct rt_mutex_waiter *waiter,
134 				     struct task_struct *task);
135 extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
136 				     struct rt_mutex_waiter *waiter,
137 				     struct task_struct *task);
138 extern int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
139 			       struct hrtimer_sleeper *to,
140 			       struct rt_mutex_waiter *waiter);
141 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
142 				 struct rt_mutex_waiter *waiter);
143 
144 extern int rt_mutex_futex_trylock(struct rt_mutex *l);
145 extern int __rt_mutex_futex_trylock(struct rt_mutex *l);
146 
147 extern void rt_mutex_futex_unlock(struct rt_mutex *lock);
148 extern bool __rt_mutex_futex_unlock(struct rt_mutex *lock,
149 				 struct wake_q_head *wqh);
150 
151 extern void rt_mutex_postunlock(struct wake_q_head *wake_q);
152 
153 #ifdef CONFIG_DEBUG_RT_MUTEXES
154 # include "rtmutex-debug.h"
155 #else
156 # include "rtmutex.h"
157 #endif
158 
159 #endif
160