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 */ 32 struct 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 */ 52 struct 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 */ 67 struct 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 */ 81 extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock, 82 struct task_struct *proxy_owner) 83 __must_hold(&lock->wait_lock); 84 85 extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock) 86 __must_hold(&lock->wait_lock); 87 88 extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock, 89 struct rt_mutex_waiter *waiter, 90 struct task_struct *task, 91 struct wake_q_head *) 92 __must_hold(&lock->wait_lock); 93 94 extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock, 95 struct rt_mutex_waiter *waiter, 96 struct task_struct *task); 97 extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock, 98 struct hrtimer_sleeper *to, 99 struct rt_mutex_waiter *waiter); 100 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock, 101 struct rt_mutex_waiter *waiter); 102 103 extern int rt_mutex_futex_trylock(struct rt_mutex_base *lock); 104 extern int __rt_mutex_futex_trylock(struct rt_mutex_base *lock) 105 __must_hold(&lock->wait_lock); 106 107 extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock); 108 extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock, 109 struct rt_wake_q_head *wqh); 110 111 extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh); 112 113 /* 114 * Must be guarded because this header is included from rcu/tree_plugin.h 115 * unconditionally. 116 */ 117 #ifdef CONFIG_RT_MUTEXES 118 static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock) 119 __must_hold(&lock->wait_lock) 120 { 121 return !RB_EMPTY_ROOT(&lock->waiters.rb_root); 122 } 123 124 /* 125 * Lockless speculative check whether @waiter is still the top waiter on 126 * @lock. This is solely comparing pointers and not derefencing the 127 * leftmost entry which might be about to vanish. 128 */ 129 static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock, 130 struct rt_mutex_waiter *waiter) 131 __must_hold(&lock->wait_lock) 132 { 133 struct rb_node *leftmost = rb_first_cached(&lock->waiters); 134 135 return rb_entry(leftmost, struct rt_mutex_waiter, tree.entry) == waiter; 136 } 137 138 static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock) 139 __must_hold(&lock->wait_lock) 140 { 141 struct rb_node *leftmost = rb_first_cached(&lock->waiters); 142 struct rt_mutex_waiter *w = NULL; 143 144 lockdep_assert_held(&lock->wait_lock); 145 146 if (leftmost) { 147 w = rb_entry(leftmost, struct rt_mutex_waiter, tree.entry); 148 BUG_ON(w->lock != lock); 149 } 150 return w; 151 } 152 153 static inline int task_has_pi_waiters(struct task_struct *p) 154 { 155 return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root); 156 } 157 158 static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p) 159 { 160 lockdep_assert_held(&p->pi_lock); 161 162 return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter, 163 pi_tree.entry); 164 } 165 166 /* 167 * Constants for rt mutex functions which have a selectable deadlock 168 * detection. 169 * 170 * RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are 171 * no further PI adjustments to be made. 172 * 173 * RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full 174 * walk of the lock chain. 175 */ 176 enum rtmutex_chainwalk { 177 RT_MUTEX_MIN_CHAINWALK, 178 RT_MUTEX_FULL_CHAINWALK, 179 }; 180 181 static inline void __rt_mutex_base_init(struct rt_mutex_base *lock) 182 { 183 scoped_guard (raw_spinlock_init, &lock->wait_lock) { 184 lock->waiters = RB_ROOT_CACHED; 185 lock->owner = NULL; 186 } 187 } 188 189 /* Debug functions */ 190 static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock) 191 { 192 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) 193 DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current); 194 } 195 196 static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock) 197 { 198 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) 199 DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock)); 200 } 201 202 static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter) 203 { 204 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) 205 memset(waiter, 0x11, sizeof(*waiter)); 206 } 207 208 static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter) 209 { 210 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) 211 memset(waiter, 0x22, sizeof(*waiter)); 212 } 213 214 static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter) 215 { 216 debug_rt_mutex_init_waiter(waiter); 217 RB_CLEAR_NODE(&waiter->pi_tree.entry); 218 RB_CLEAR_NODE(&waiter->tree.entry); 219 waiter->wake_state = TASK_NORMAL; 220 waiter->task = NULL; 221 } 222 223 static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter) 224 { 225 rt_mutex_init_waiter(waiter); 226 waiter->wake_state = TASK_RTLOCK_WAIT; 227 } 228 229 #else /* CONFIG_RT_MUTEXES */ 230 /* Used in rcu/tree_plugin.h */ 231 static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock) 232 { 233 return NULL; 234 } 235 #endif /* !CONFIG_RT_MUTEXES */ 236 237 #endif 238