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 };
38 
39 /*
40  * Various helpers to access the waiters-tree:
41  */
42 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
43 {
44 	return !RB_EMPTY_ROOT(&lock->waiters);
45 }
46 
47 static inline struct rt_mutex_waiter *
48 rt_mutex_top_waiter(struct rt_mutex *lock)
49 {
50 	struct rt_mutex_waiter *w;
51 
52 	w = rb_entry(lock->waiters_leftmost, struct rt_mutex_waiter,
53 		     tree_entry);
54 	BUG_ON(w->lock != lock);
55 
56 	return w;
57 }
58 
59 static inline int task_has_pi_waiters(struct task_struct *p)
60 {
61 	return !RB_EMPTY_ROOT(&p->pi_waiters);
62 }
63 
64 static inline struct rt_mutex_waiter *
65 task_top_pi_waiter(struct task_struct *p)
66 {
67 	return rb_entry(p->pi_waiters_leftmost, struct rt_mutex_waiter,
68 			pi_tree_entry);
69 }
70 
71 /*
72  * lock->owner state tracking:
73  */
74 #define RT_MUTEX_HAS_WAITERS	1UL
75 
76 static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
77 {
78 	unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
79 
80 	return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
81 }
82 
83 /*
84  * Constants for rt mutex functions which have a selectable deadlock
85  * detection.
86  *
87  * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
88  *				no further PI adjustments to be made.
89  *
90  * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
91  *				walk of the lock chain.
92  */
93 enum rtmutex_chainwalk {
94 	RT_MUTEX_MIN_CHAINWALK,
95 	RT_MUTEX_FULL_CHAINWALK,
96 };
97 
98 /*
99  * PI-futex support (proxy locking functions, etc.):
100  */
101 extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
102 extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
103 				       struct task_struct *proxy_owner);
104 extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
105 				  struct task_struct *proxy_owner);
106 extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
107 				     struct rt_mutex_waiter *waiter,
108 				     struct task_struct *task);
109 extern int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
110 				      struct hrtimer_sleeper *to,
111 				      struct rt_mutex_waiter *waiter);
112 extern int rt_mutex_timed_futex_lock(struct rt_mutex *l, struct hrtimer_sleeper *to);
113 extern bool rt_mutex_futex_unlock(struct rt_mutex *lock,
114 				  struct wake_q_head *wqh);
115 extern void rt_mutex_adjust_prio(struct task_struct *task);
116 
117 #ifdef CONFIG_DEBUG_RT_MUTEXES
118 # include "rtmutex-debug.h"
119 #else
120 # include "rtmutex.h"
121 #endif
122 
123 #endif
124