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/debug_locks.h>
 17#include <linux/rtmutex.h>
 18#include <linux/sched/wake_q.h>
 19
 20/*
 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.
 23 *
 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
 31 * @ww_ctx:		WW context pointer
 32 */
 33struct rt_mutex_waiter {
 34	struct rb_node		tree_entry;
 35	struct rb_node		pi_tree_entry;
 36	struct task_struct	*task;
 37	struct rt_mutex_base	*lock;
 38	unsigned int		wake_state;
 39	int			prio;
 40	u64			deadline;
 41	struct ww_acquire_ctx	*ww_ctx;
 42};
 43
 44/**
 45 * rt_wake_q_head - Wrapper around regular wake_q_head to support
 46 *		    "sleeping" spinlocks on RT
 47 * @head:		The regular wake_q_head for sleeping lock variants
 48 * @rtlock_task:	Task pointer for RT lock (spin/rwlock) wakeups
 49 */
 50struct rt_wake_q_head {
 51	struct wake_q_head	head;
 52	struct task_struct	*rtlock_task;
 53};
 54
 55#define DEFINE_RT_WAKE_Q(name)						\
 56	struct rt_wake_q_head name = {					\
 57		.head		= WAKE_Q_HEAD_INITIALIZER(name.head),	\
 58		.rtlock_task	= NULL,					\
 59	}
 60
 61/*
 62 * PI-futex support (proxy locking functions, etc.):
 63 */
 64extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
 65				       struct task_struct *proxy_owner);
 66extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock);
 67extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
 68				     struct rt_mutex_waiter *waiter,
 69				     struct task_struct *task);
 70extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
 71				     struct rt_mutex_waiter *waiter,
 72				     struct task_struct *task);
 73extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
 74			       struct hrtimer_sleeper *to,
 75			       struct rt_mutex_waiter *waiter);
 76extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
 77				 struct rt_mutex_waiter *waiter);
 78
 79extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
 80extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
 81
 82extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
 83extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
 84				struct rt_wake_q_head *wqh);
 85
 86extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh);
 87
 88/*
 89 * Must be guarded because this header is included from rcu/tree_plugin.h
 90 * unconditionally.
 91 */
 92#ifdef CONFIG_RT_MUTEXES
 93static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
 94{
 95	return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
 96}
 97
 98/*
 99 * Lockless speculative check whether @waiter is still the top waiter on
100 * @lock. This is solely comparing pointers and not derefencing the
101 * leftmost entry which might be about to vanish.
102 */
103static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock,
104						 struct rt_mutex_waiter *waiter)
105{
106	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
107
108	return rb_entry(leftmost, struct rt_mutex_waiter, tree_entry) == waiter;
109}
110
111static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
112{
113	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
114	struct rt_mutex_waiter *w = NULL;
115
116	if (leftmost) {
117		w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
118		BUG_ON(w->lock != lock);
119	}
120	return w;
121}
122
123static inline int task_has_pi_waiters(struct task_struct *p)
124{
125	return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
126}
127
128static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
129{
130	return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
131			pi_tree_entry);
132}
133
134#define RT_MUTEX_HAS_WAITERS	1UL
135
136static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
137{
138	unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
139
140	return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
141}
142
143/*
144 * Constants for rt mutex functions which have a selectable deadlock
145 * detection.
146 *
147 * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
148 *				no further PI adjustments to be made.
149 *
150 * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
151 *				walk of the lock chain.
152 */
153enum rtmutex_chainwalk {
154	RT_MUTEX_MIN_CHAINWALK,
155	RT_MUTEX_FULL_CHAINWALK,
156};
157
158static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
159{
160	raw_spin_lock_init(&lock->wait_lock);
161	lock->waiters = RB_ROOT_CACHED;
162	lock->owner = NULL;
163}
164
165/* Debug functions */
166static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock)
167{
168	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
169		DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
170}
171
172static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
173{
174	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
175		DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
176}
177
178static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
179{
180	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
181		memset(waiter, 0x11, sizeof(*waiter));
182}
183
184static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
185{
186	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
187		memset(waiter, 0x22, sizeof(*waiter));
188}
189
190static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
191{
192	debug_rt_mutex_init_waiter(waiter);
193	RB_CLEAR_NODE(&waiter->pi_tree_entry);
194	RB_CLEAR_NODE(&waiter->tree_entry);
195	waiter->wake_state = TASK_NORMAL;
196	waiter->task = NULL;
197}
198
199static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter)
200{
201	rt_mutex_init_waiter(waiter);
202	waiter->wake_state = TASK_RTLOCK_WAIT;
203}
204
205#else /* CONFIG_RT_MUTEXES */
206/* Used in rcu/tree_plugin.h */
207static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
208{
209	return NULL;
210}
211#endif  /* !CONFIG_RT_MUTEXES */
212
213#endif