1 /* SPDX-License-Identifier: GPL-2.0 */
3 * RT Mutexes: blocking mutual exclusion locks with PI support
5 * started by Ingo Molnar and Thomas Gleixner:
7 * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
8 * Copyright (C) 2006, Timesys Corp., Thomas Gleixner <tglx@timesys.com>
10 * This file contains the private data structure and API definitions.
13 #ifndef __KERNEL_RTMUTEX_COMMON_H
14 #define __KERNEL_RTMUTEX_COMMON_H
16 #include <linux/debug_locks.h>
17 #include <linux/rtmutex.h>
18 #include <linux/sched/wake_q.h>
21 * This is the control structure for tasks blocked on a rt_mutex,
22 * which is allocated on the kernel stack on of the blocked task.
24 * @tree_entry: pi node to enqueue into the mutex waiters tree
25 * @pi_tree_entry: pi node to enqueue into the mutex owner waiters tree
26 * @task: task reference to the blocked task
27 * @lock: Pointer to the rt_mutex on which the waiter blocks
28 * @wake_state: Wakeup state to use (TASK_NORMAL or TASK_RTLOCK_WAIT)
29 * @prio: Priority of the waiter
30 * @deadline: Deadline of the waiter if applicable
32 struct rt_mutex_waiter {
33 struct rb_node tree_entry;
34 struct rb_node pi_tree_entry;
35 struct task_struct *task;
36 struct rt_mutex_base *lock;
37 unsigned int wake_state;
43 * rt_wake_q_head - Wrapper around regular wake_q_head to support
44 * "sleeping" spinlocks on RT
45 * @head: The regular wake_q_head for sleeping lock variants
46 * @rtlock_task: Task pointer for RT lock (spin/rwlock) wakeups
48 struct rt_wake_q_head {
49 struct wake_q_head head;
50 struct task_struct *rtlock_task;
53 #define DEFINE_RT_WAKE_Q(name) \
54 struct rt_wake_q_head name = { \
55 .head = WAKE_Q_HEAD_INITIALIZER(name.head), \
56 .rtlock_task = NULL, \
60 * PI-futex support (proxy locking functions, etc.):
62 extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
63 struct task_struct *proxy_owner);
64 extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock);
65 extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
66 struct rt_mutex_waiter *waiter,
67 struct task_struct *task);
68 extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
69 struct rt_mutex_waiter *waiter,
70 struct task_struct *task);
71 extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
72 struct hrtimer_sleeper *to,
73 struct rt_mutex_waiter *waiter);
74 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
75 struct rt_mutex_waiter *waiter);
77 extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
78 extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
80 extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
81 extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
82 struct rt_wake_q_head *wqh);
84 extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh);
87 * Must be guarded because this header is included from rcu/tree_plugin.h
90 #ifdef CONFIG_RT_MUTEXES
91 static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
93 return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
96 static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
98 struct rb_node *leftmost = rb_first_cached(&lock->waiters);
99 struct rt_mutex_waiter *w = NULL;
102 w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
103 BUG_ON(w->lock != lock);
108 static inline int task_has_pi_waiters(struct task_struct *p)
110 return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
113 static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
115 return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
119 #define RT_MUTEX_HAS_WAITERS 1UL
121 static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
123 unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
125 return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
129 * Constants for rt mutex functions which have a selectable deadlock
132 * RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are
133 * no further PI adjustments to be made.
135 * RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full
136 * walk of the lock chain.
138 enum rtmutex_chainwalk {
139 RT_MUTEX_MIN_CHAINWALK,
140 RT_MUTEX_FULL_CHAINWALK,
143 static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
145 raw_spin_lock_init(&lock->wait_lock);
146 lock->waiters = RB_ROOT_CACHED;
150 /* Debug functions */
151 static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock)
153 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
154 DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
157 static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
159 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
160 DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
163 static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
165 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
166 memset(waiter, 0x11, sizeof(*waiter));
169 static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
171 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
172 memset(waiter, 0x22, sizeof(*waiter));
175 static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
177 debug_rt_mutex_init_waiter(waiter);
178 RB_CLEAR_NODE(&waiter->pi_tree_entry);
179 RB_CLEAR_NODE(&waiter->tree_entry);
180 waiter->wake_state = TASK_NORMAL;
184 static inline void rtlock_init_rtmutex_waiter(struct rt_mutex_waiter *waiter)
186 rt_mutex_init_waiter(waiter);
187 waiter->wake_state = TASK_RTLOCK_WAIT;
190 #else /* CONFIG_RT_MUTEXES */
191 /* Used in rcu/tree_plugin.h */
192 static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
196 #endif /* !CONFIG_RT_MUTEXES */