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/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 #ifdef CONFIG_DEBUG_RT_MUTEXES
33 	unsigned long		ip;
34 	struct pid		*deadlock_task_pid;
35 	struct rt_mutex		*deadlock_lock;
36 #endif
37 	int prio;
38 	u64 deadline;
39 };
40 
41 /*
42  * Various helpers to access the waiters-tree:
43  */
44 
45 #ifdef CONFIG_RT_MUTEXES
46 
47 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
48 {
49 	return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
50 }
51 
52 static inline struct rt_mutex_waiter *
53 rt_mutex_top_waiter(struct rt_mutex *lock)
54 {
55 	struct rt_mutex_waiter *w;
56 
57 	w = rb_entry(lock->waiters.rb_leftmost,
58 		     struct rt_mutex_waiter, tree_entry);
59 	BUG_ON(w->lock != lock);
60 
61 	return w;
62 }
63 
64 static inline int task_has_pi_waiters(struct task_struct *p)
65 {
66 	return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
67 }
68 
69 static inline struct rt_mutex_waiter *
70 task_top_pi_waiter(struct task_struct *p)
71 {
72 	return rb_entry(p->pi_waiters.rb_leftmost,
73 			struct rt_mutex_waiter, pi_tree_entry);
74 }
75 
76 #else
77 
78 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
79 {
80 	return false;
81 }
82 
83 static inline struct rt_mutex_waiter *
84 rt_mutex_top_waiter(struct rt_mutex *lock)
85 {
86 	return NULL;
87 }
88 
89 static inline int task_has_pi_waiters(struct task_struct *p)
90 {
91 	return false;
92 }
93 
94 static inline struct rt_mutex_waiter *
95 task_top_pi_waiter(struct task_struct *p)
96 {
97 	return NULL;
98 }
99 
100 #endif
101 
102 /*
103  * lock->owner state tracking:
104  */
105 #define RT_MUTEX_HAS_WAITERS	1UL
106 
107 static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
108 {
109 	unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
110 
111 	return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
112 }
113 
114 /*
115  * Constants for rt mutex functions which have a selectable deadlock
116  * detection.
117  *
118  * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
119  *				no further PI adjustments to be made.
120  *
121  * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
122  *				walk of the lock chain.
123  */
124 enum rtmutex_chainwalk {
125 	RT_MUTEX_MIN_CHAINWALK,
126 	RT_MUTEX_FULL_CHAINWALK,
127 };
128 
129 /*
130  * PI-futex support (proxy locking functions, etc.):
131  */
132 extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
133 extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
134 				       struct task_struct *proxy_owner);
135 extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
136 				  struct task_struct *proxy_owner);
137 extern void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter);
138 extern int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
139 				     struct rt_mutex_waiter *waiter,
140 				     struct task_struct *task);
141 extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
142 				     struct rt_mutex_waiter *waiter,
143 				     struct task_struct *task);
144 extern int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
145 			       struct hrtimer_sleeper *to,
146 			       struct rt_mutex_waiter *waiter);
147 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
148 				 struct rt_mutex_waiter *waiter);
149 
150 extern int rt_mutex_futex_trylock(struct rt_mutex *l);
151 extern int __rt_mutex_futex_trylock(struct rt_mutex *l);
152 
153 extern void rt_mutex_futex_unlock(struct rt_mutex *lock);
154 extern bool __rt_mutex_futex_unlock(struct rt_mutex *lock,
155 				 struct wake_q_head *wqh);
156 
157 extern void rt_mutex_postunlock(struct wake_q_head *wake_q);
158 
159 #ifdef CONFIG_DEBUG_RT_MUTEXES
160 # include "rtmutex-debug.h"
161 #else
162 # include "rtmutex.h"
163 #endif
164 
165 #endif
166