1 /*
2  * RT Mutexes: blocking mutual exclusion locks with PI support
3  *
4  * started by Ingo Molnar and Thomas Gleixner:
5  *
6  *  Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
7  *  Copyright (C) 2006, Timesys Corp., Thomas Gleixner <tglx@timesys.com>
8  *
9  * This file contains the private data structure and API definitions.
10  */
11 
12 #ifndef __KERNEL_RTMUTEX_COMMON_H
13 #define __KERNEL_RTMUTEX_COMMON_H
14 
15 #include <linux/rtmutex.h>
16 #include <linux/sched/wake_q.h>
17 
18 /*
19  * This is the control structure for tasks blocked on a rt_mutex,
20  * which is allocated on the kernel stack on of the blocked task.
21  *
22  * @tree_entry:		pi node to enqueue into the mutex waiters tree
23  * @pi_tree_entry:	pi node to enqueue into the mutex owner waiters tree
24  * @task:		task reference to the blocked task
25  */
26 struct rt_mutex_waiter {
27 	struct rb_node          tree_entry;
28 	struct rb_node          pi_tree_entry;
29 	struct task_struct	*task;
30 	struct rt_mutex		*lock;
31 #ifdef CONFIG_DEBUG_RT_MUTEXES
32 	unsigned long		ip;
33 	struct pid		*deadlock_task_pid;
34 	struct rt_mutex		*deadlock_lock;
35 #endif
36 	int prio;
37 	u64 deadline;
38 };
39 
40 /*
41  * Various helpers to access the waiters-tree:
42  */
43 
44 #ifdef CONFIG_RT_MUTEXES
45 
46 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
47 {
48 	return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
49 }
50 
51 static inline struct rt_mutex_waiter *
52 rt_mutex_top_waiter(struct rt_mutex *lock)
53 {
54 	struct rt_mutex_waiter *w;
55 
56 	w = rb_entry(lock->waiters.rb_leftmost,
57 		     struct rt_mutex_waiter, tree_entry);
58 	BUG_ON(w->lock != lock);
59 
60 	return w;
61 }
62 
63 static inline int task_has_pi_waiters(struct task_struct *p)
64 {
65 	return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
66 }
67 
68 static inline struct rt_mutex_waiter *
69 task_top_pi_waiter(struct task_struct *p)
70 {
71 	return rb_entry(p->pi_waiters.rb_leftmost,
72 			struct rt_mutex_waiter, pi_tree_entry);
73 }
74 
75 #else
76 
77 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
78 {
79 	return false;
80 }
81 
82 static inline struct rt_mutex_waiter *
83 rt_mutex_top_waiter(struct rt_mutex *lock)
84 {
85 	return NULL;
86 }
87 
88 static inline int task_has_pi_waiters(struct task_struct *p)
89 {
90 	return false;
91 }
92 
93 static inline struct rt_mutex_waiter *
94 task_top_pi_waiter(struct task_struct *p)
95 {
96 	return NULL;
97 }
98 
99 #endif
100 
101 /*
102  * lock->owner state tracking:
103  */
104 #define RT_MUTEX_HAS_WAITERS	1UL
105 
106 static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
107 {
108 	unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
109 
110 	return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
111 }
112 
113 /*
114  * Constants for rt mutex functions which have a selectable deadlock
115  * detection.
116  *
117  * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
118  *				no further PI adjustments to be made.
119  *
120  * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
121  *				walk of the lock chain.
122  */
123 enum rtmutex_chainwalk {
124 	RT_MUTEX_MIN_CHAINWALK,
125 	RT_MUTEX_FULL_CHAINWALK,
126 };
127 
128 /*
129  * PI-futex support (proxy locking functions, etc.):
130  */
131 extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
132 extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
133 				       struct task_struct *proxy_owner);
134 extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
135 				  struct task_struct *proxy_owner);
136 extern void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter);
137 extern int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
138 				     struct rt_mutex_waiter *waiter,
139 				     struct task_struct *task);
140 extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
141 				     struct rt_mutex_waiter *waiter,
142 				     struct task_struct *task);
143 extern int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
144 			       struct hrtimer_sleeper *to,
145 			       struct rt_mutex_waiter *waiter);
146 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
147 				 struct rt_mutex_waiter *waiter);
148 
149 extern int rt_mutex_futex_trylock(struct rt_mutex *l);
150 
151 extern void rt_mutex_futex_unlock(struct rt_mutex *lock);
152 extern bool __rt_mutex_futex_unlock(struct rt_mutex *lock,
153 				 struct wake_q_head *wqh);
154 
155 extern void rt_mutex_postunlock(struct wake_q_head *wake_q);
156 
157 #ifdef CONFIG_DEBUG_RT_MUTEXES
158 # include "rtmutex-debug.h"
159 #else
160 # include "rtmutex.h"
161 #endif
162 
163 #endif
164