rtmutex_common.h

  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/*
 22 * This is a helper for the struct rt_mutex_waiter below. A waiter goes in two
 23 * separate trees and they need their own copy of the sort keys because of
 24 * different locking requirements.
 25 *
 26 * @entry:		rbtree node to enqueue into the waiters tree
 27 * @prio:		Priority of the waiter
 28 * @deadline:		Deadline of the waiter if applicable
 29 *
 30 * See rt_waiter_node_less() and waiter_*_prio().
 31 */
 32struct rt_waiter_node {
 33	struct rb_node	entry;
 34	int		prio;
 35	u64		deadline;
 36};
 37
 38/*
 39 * This is the control structure for tasks blocked on a rt_mutex,
 40 * which is allocated on the kernel stack on of the blocked task.
 41 *
 42 * @tree:		node to enqueue into the mutex waiters tree
 43 * @pi_tree:		node to enqueue into the mutex owner waiters tree
 44 * @task:		task reference to the blocked task
 45 * @lock:		Pointer to the rt_mutex on which the waiter blocks
 46 * @wake_state:		Wakeup state to use (TASK_NORMAL or TASK_RTLOCK_WAIT)
 47 * @ww_ctx:		WW context pointer
 48 *
 49 * @tree is ordered by @lock->wait_lock
 50 * @pi_tree is ordered by rt_mutex_owner(@lock)->pi_lock
 51 */
 52struct rt_mutex_waiter {
 53	struct rt_waiter_node	tree;
 54	struct rt_waiter_node	pi_tree;
 55	struct task_struct	*task;
 56	struct rt_mutex_base	*lock;
 57	unsigned int		wake_state;
 58	struct ww_acquire_ctx	*ww_ctx;
 59};
 60
 61/**
 62 * struct rt_wake_q_head - Wrapper around regular wake_q_head to support
 63 *			   "sleeping" spinlocks on RT
 64 * @head:		The regular wake_q_head for sleeping lock variants
 65 * @rtlock_task:	Task pointer for RT lock (spin/rwlock) wakeups
 66 */
 67struct rt_wake_q_head {
 68	struct wake_q_head	head;
 69	struct task_struct	*rtlock_task;
 70};
 71
 72#define DEFINE_RT_WAKE_Q(name)						\
 73	struct rt_wake_q_head name = {					\
 74		.head		= WAKE_Q_HEAD_INITIALIZER(name.head),	\
 75		.rtlock_task	= NULL,					\
 76	}
 77
 78/*
 79 * PI-futex support (proxy locking functions, etc.):
 80 */
 81extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
 82				       struct task_struct *proxy_owner);
 83extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock);
 84extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
 85				     struct rt_mutex_waiter *waiter,
 86				     struct task_struct *task,
 87				     struct wake_q_head *);
 88extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
 89				     struct rt_mutex_waiter *waiter,
 90				     struct task_struct *task);
 91extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
 92			       struct hrtimer_sleeper *to,
 93			       struct rt_mutex_waiter *waiter);
 94extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
 95				 struct rt_mutex_waiter *waiter);
 96
 97extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
 98extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
 99
100extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
101extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
102				struct rt_wake_q_head *wqh);
103
104extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh);
105
106/*
107 * Must be guarded because this header is included from rcu/tree_plugin.h
108 * unconditionally.
109 */
110#ifdef CONFIG_RT_MUTEXES
111static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
112{
113	return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
114}
115
116/*
117 * Lockless speculative check whether @waiter is still the top waiter on
118 * @lock. This is solely comparing pointers and not derefencing the
119 * leftmost entry which might be about to vanish.
120 */
121static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock,
122						 struct rt_mutex_waiter *waiter)
123{
124	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
125
126	return rb_entry(leftmost, struct rt_mutex_waiter, tree.entry) == waiter;
127}
128
129static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
130{
131	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
132	struct rt_mutex_waiter *w = NULL;
133
134	lockdep_assert_held(&lock->wait_lock);
135
136	if (leftmost) {
137		w = rb_entry(leftmost, struct rt_mutex_waiter, tree.entry);
138		BUG_ON(w->lock != lock);
139	}
140	return w;
141}
142
143static inline int task_has_pi_waiters(struct task_struct *p)
144{
145	return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
146}
147
148static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
149{
150	lockdep_assert_held(&p->pi_lock);
151
152	return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
153			pi_tree.entry);
154}
155
156/*
157 * Constants for rt mutex functions which have a selectable deadlock
158 * detection.
159 *
160 * RT_MUTEX_MIN_CHAINWALK:	Stops the lock chain walk when there are
161 *				no further PI adjustments to be made.
162 *
163 * RT_MUTEX_FULL_CHAINWALK:	Invoke deadlock detection with a full
164 *				walk of the lock chain.
165 */
166enum rtmutex_chainwalk {
167	RT_MUTEX_MIN_CHAINWALK,
168	RT_MUTEX_FULL_CHAINWALK,
169};
170
171static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
172{
173	raw_spin_lock_init(&lock->wait_lock);
174	lock->waiters = RB_ROOT_CACHED;
175	lock->owner = NULL;
176}
177
178/* Debug functions */
179static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock)
180{
181	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
182		DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
183}
184
185static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
186{
187	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
188		DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
189}
190
191static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
192{
193	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
194		memset(waiter, 0x11, sizeof(*waiter));
195}
196
197static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
198{
199	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
200		memset(waiter, 0x22, sizeof(*waiter));
201}
202
203static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
204{
205	debug_rt_mutex_init_waiter(waiter);
206	RB_CLEAR_NODE(&waiter->pi_tree.entry);
207	RB_CLEAR_NODE(&waiter->tree.entry);
208	waiter->wake_state = TASK_NORMAL;
209	waiter->task = NULL;
210}
211
212static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter)
213{
214	rt_mutex_init_waiter(waiter);
215	waiter->wake_state = TASK_RTLOCK_WAIT;
216}
217
218#else /* CONFIG_RT_MUTEXES */
219/* Used in rcu/tree_plugin.h */
220static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
221{
222	return NULL;
223}
224#endif  /* !CONFIG_RT_MUTEXES */
225
226#endif