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 */ 33 struct 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 */ 50 struct 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 */ 64 extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock, 65 struct task_struct *proxy_owner); 66 extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock); 67 extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock, 68 struct rt_mutex_waiter *waiter, 69 struct task_struct *task); 70 extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock, 71 struct rt_mutex_waiter *waiter, 72 struct task_struct *task); 73 extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock, 74 struct hrtimer_sleeper *to, 75 struct rt_mutex_waiter *waiter); 76 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock, 77 struct rt_mutex_waiter *waiter); 78 79 extern int rt_mutex_futex_trylock(struct rt_mutex_base *l); 80 extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l); 81 82 extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock); 83 extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock, 84 struct rt_wake_q_head *wqh); 85 86 extern 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 93 static 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 */ 103 static 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 } 110 111 static 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 } 122 123 static inline int task_has_pi_waiters(struct task_struct *p) 124 { 125 return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root); 126 } 127 128 static 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 135 136 static 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 */ 153 enum rtmutex_chainwalk { 154 RT_MUTEX_MIN_CHAINWALK, 155 RT_MUTEX_FULL_CHAINWALK, 156 }; 157 158 static 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 */ 166 static 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 } 171 172 static 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 } 177 178 static 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 } 183 184 static 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 } 189 190 static 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 } 198 199 static 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 */ 207 static 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 214