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
rt_mutex_has_waiters(struct rt_mutex * lock)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 *
rt_mutex_top_waiter(struct rt_mutex * lock)53 rt_mutex_top_waiter(struct rt_mutex *lock)
54 {
55 struct rb_node *leftmost = rb_first_cached(&lock->waiters);
56 struct rt_mutex_waiter *w = NULL;
57
58 if (leftmost) {
59 w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
60 BUG_ON(w->lock != lock);
61 }
62 return w;
63 }
64
task_has_pi_waiters(struct task_struct * p)65 static inline int task_has_pi_waiters(struct task_struct *p)
66 {
67 return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
68 }
69
70 static inline struct rt_mutex_waiter *
task_top_pi_waiter(struct task_struct * p)71 task_top_pi_waiter(struct task_struct *p)
72 {
73 return rb_entry(p->pi_waiters.rb_leftmost,
74 struct rt_mutex_waiter, pi_tree_entry);
75 }
76
77 #else
78
rt_mutex_has_waiters(struct rt_mutex * lock)79 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
80 {
81 return false;
82 }
83
84 static inline struct rt_mutex_waiter *
rt_mutex_top_waiter(struct rt_mutex * lock)85 rt_mutex_top_waiter(struct rt_mutex *lock)
86 {
87 return NULL;
88 }
89
task_has_pi_waiters(struct task_struct * p)90 static inline int task_has_pi_waiters(struct task_struct *p)
91 {
92 return false;
93 }
94
95 static inline struct rt_mutex_waiter *
task_top_pi_waiter(struct task_struct * p)96 task_top_pi_waiter(struct task_struct *p)
97 {
98 return NULL;
99 }
100
101 #endif
102
103 /*
104 * lock->owner state tracking:
105 */
106 #define RT_MUTEX_HAS_WAITERS 1UL
107
rt_mutex_owner(struct rt_mutex * lock)108 static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
109 {
110 unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
111
112 return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
113 }
114
115 /*
116 * Constants for rt mutex functions which have a selectable deadlock
117 * detection.
118 *
119 * RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are
120 * no further PI adjustments to be made.
121 *
122 * RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full
123 * walk of the lock chain.
124 */
125 enum rtmutex_chainwalk {
126 RT_MUTEX_MIN_CHAINWALK,
127 RT_MUTEX_FULL_CHAINWALK,
128 };
129
130 /*
131 * PI-futex support (proxy locking functions, etc.):
132 */
133 extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
134 extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
135 struct task_struct *proxy_owner);
136 extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
137 struct task_struct *proxy_owner);
138 extern void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter);
139 extern int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
140 struct rt_mutex_waiter *waiter,
141 struct task_struct *task);
142 extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
143 struct rt_mutex_waiter *waiter,
144 struct task_struct *task);
145 extern int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
146 struct hrtimer_sleeper *to,
147 struct rt_mutex_waiter *waiter);
148 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
149 struct rt_mutex_waiter *waiter);
150
151 extern int rt_mutex_futex_trylock(struct rt_mutex *l);
152 extern int __rt_mutex_futex_trylock(struct rt_mutex *l);
153
154 extern void rt_mutex_futex_unlock(struct rt_mutex *lock);
155 extern bool __rt_mutex_futex_unlock(struct rt_mutex *lock,
156 struct wake_q_head *wqh);
157
158 extern void rt_mutex_postunlock(struct wake_q_head *wake_q);
159
160 #ifdef CONFIG_DEBUG_RT_MUTEXES
161 # include "rtmutex-debug.h"
162 #else
163 # include "rtmutex.h"
164 #endif
165
166 #endif
167