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 * @prio: Priority of the waiter
29 * @deadline: Deadline of the waiter if applicable
31 struct rt_mutex_waiter {
32 struct rb_node tree_entry;
33 struct rb_node pi_tree_entry;
34 struct task_struct *task;
35 struct rt_mutex *lock;
41 * Must be guarded because this header is included from rcu/tree_plugin.h
44 #ifdef CONFIG_RT_MUTEXES
45 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
47 return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
50 static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex *lock)
52 struct rb_node *leftmost = rb_first_cached(&lock->waiters);
53 struct rt_mutex_waiter *w = NULL;
56 w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
57 BUG_ON(w->lock != lock);
62 static inline int task_has_pi_waiters(struct task_struct *p)
64 return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
67 static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
69 return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
73 #define RT_MUTEX_HAS_WAITERS 1UL
75 static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
77 unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
79 return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
81 #else /* CONFIG_RT_MUTEXES */
82 /* Used in rcu/tree_plugin.h */
83 static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
87 #endif /* !CONFIG_RT_MUTEXES */
90 * Constants for rt mutex functions which have a selectable deadlock
93 * RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are
94 * no further PI adjustments to be made.
96 * RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full
97 * walk of the lock chain.
99 enum rtmutex_chainwalk {
100 RT_MUTEX_MIN_CHAINWALK,
101 RT_MUTEX_FULL_CHAINWALK,
104 static inline void __rt_mutex_basic_init(struct rt_mutex *lock)
107 raw_spin_lock_init(&lock->wait_lock);
108 lock->waiters = RB_ROOT_CACHED;
112 * PI-futex support (proxy locking functions, etc.):
114 extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
115 struct task_struct *proxy_owner);
116 extern void rt_mutex_proxy_unlock(struct rt_mutex *lock);
117 extern void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter);
118 extern int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
119 struct rt_mutex_waiter *waiter,
120 struct task_struct *task);
121 extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
122 struct rt_mutex_waiter *waiter,
123 struct task_struct *task);
124 extern int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
125 struct hrtimer_sleeper *to,
126 struct rt_mutex_waiter *waiter);
127 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
128 struct rt_mutex_waiter *waiter);
130 extern int rt_mutex_futex_trylock(struct rt_mutex *l);
131 extern int __rt_mutex_futex_trylock(struct rt_mutex *l);
133 extern void rt_mutex_futex_unlock(struct rt_mutex *lock);
134 extern bool __rt_mutex_futex_unlock(struct rt_mutex *lock,
135 struct wake_q_head *wqh);
137 extern void rt_mutex_postunlock(struct wake_q_head *wake_q);
139 /* Debug functions */
140 static inline void debug_rt_mutex_unlock(struct rt_mutex *lock)
142 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
143 DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
146 static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
148 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
149 DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
152 static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
154 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
155 memset(waiter, 0x11, sizeof(*waiter));
158 static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
160 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
161 memset(waiter, 0x22, sizeof(*waiter));