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 
17 /*
18  * This is the control structure for tasks blocked on a rt_mutex,
19  * which is allocated on the kernel stack on of the blocked task.
20  *
21  * @tree_entry:		pi node to enqueue into the mutex waiters tree
22  * @pi_tree_entry:	pi node to enqueue into the mutex owner waiters tree
23  * @task:		task reference to the blocked task
24  */
25 struct rt_mutex_waiter {
26 	struct rb_node          tree_entry;
27 	struct rb_node          pi_tree_entry;
28 	struct task_struct	*task;
29 	struct rt_mutex		*lock;
30 #ifdef CONFIG_DEBUG_RT_MUTEXES
31 	unsigned long		ip;
32 	struct pid		*deadlock_task_pid;
33 	struct rt_mutex		*deadlock_lock;
34 #endif
35 	int prio;
36 };
37 
38 /*
39  * Various helpers to access the waiters-tree:
40  */
41 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
42 {
43 	return !RB_EMPTY_ROOT(&lock->waiters);
44 }
45 
46 static inline struct rt_mutex_waiter *
47 rt_mutex_top_waiter(struct rt_mutex *lock)
48 {
49 	struct rt_mutex_waiter *w;
50 
51 	w = rb_entry(lock->waiters_leftmost, struct rt_mutex_waiter,
52 		     tree_entry);
53 	BUG_ON(w->lock != lock);
54 
55 	return w;
56 }
57 
58 static inline int task_has_pi_waiters(struct task_struct *p)
59 {
60 	return !RB_EMPTY_ROOT(&p->pi_waiters);
61 }
62 
63 static inline struct rt_mutex_waiter *
64 task_top_pi_waiter(struct task_struct *p)
65 {
66 	return rb_entry(p->pi_waiters_leftmost, struct rt_mutex_waiter,
67 			pi_tree_entry);
68 }
69 
70 /*
71  * lock->owner state tracking:
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 
82 /*
83  * Constants for rt mutex functions which have a selectable deadlock
84  * detection.
85  *
86  * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
87  *				no further PI adjustments to be made.
88  *
89  * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
90  *				walk of the lock chain.
91  */
92 enum rtmutex_chainwalk {
93 	RT_MUTEX_MIN_CHAINWALK,
94 	RT_MUTEX_FULL_CHAINWALK,
95 };
96 
97 /*
98  * PI-futex support (proxy locking functions, etc.):
99  */
100 extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
101 extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
102 				       struct task_struct *proxy_owner);
103 extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
104 				  struct task_struct *proxy_owner);
105 extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
106 				     struct rt_mutex_waiter *waiter,
107 				     struct task_struct *task);
108 extern int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
109 				      struct hrtimer_sleeper *to,
110 				      struct rt_mutex_waiter *waiter);
111 extern int rt_mutex_timed_futex_lock(struct rt_mutex *l, struct hrtimer_sleeper *to);
112 extern bool rt_mutex_futex_unlock(struct rt_mutex *lock,
113 				  struct wake_q_head *wqh);
114 extern void rt_mutex_adjust_prio(struct task_struct *task);
115 
116 #ifdef CONFIG_DEBUG_RT_MUTEXES
117 # include "rtmutex-debug.h"
118 #else
119 # include "rtmutex.h"
120 #endif
121 
122 #endif
123