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 * @prio: Priority of the waiter 29 * @deadline: Deadline of the waiter if applicable 30 */ 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; 36 int prio; 37 u64 deadline; 38 }; 39 40 /* 41 * Must be guarded because this header is included from rcu/tree_plugin.h 42 * unconditionally. 43 */ 44 #ifdef CONFIG_RT_MUTEXES 45 static inline int rt_mutex_has_waiters(struct rt_mutex *lock) 46 { 47 return !RB_EMPTY_ROOT(&lock->waiters.rb_root); 48 } 49 50 static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex *lock) 51 { 52 struct rb_node *leftmost = rb_first_cached(&lock->waiters); 53 struct rt_mutex_waiter *w = NULL; 54 55 if (leftmost) { 56 w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry); 57 BUG_ON(w->lock != lock); 58 } 59 return w; 60 } 61 62 static inline int task_has_pi_waiters(struct task_struct *p) 63 { 64 return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root); 65 } 66 67 static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p) 68 { 69 return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter, 70 pi_tree_entry); 71 } 72 73 #define RT_MUTEX_HAS_WAITERS 1UL 74 75 static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock) 76 { 77 unsigned long owner = (unsigned long) READ_ONCE(lock->owner); 78 79 return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS); 80 } 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) 84 { 85 return NULL; 86 } 87 #endif /* !CONFIG_RT_MUTEXES */ 88 89 /* 90 * Constants for rt mutex functions which have a selectable deadlock 91 * detection. 92 * 93 * RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are 94 * no further PI adjustments to be made. 95 * 96 * RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full 97 * walk of the lock chain. 98 */ 99 enum rtmutex_chainwalk { 100 RT_MUTEX_MIN_CHAINWALK, 101 RT_MUTEX_FULL_CHAINWALK, 102 }; 103 104 static inline void __rt_mutex_basic_init(struct rt_mutex *lock) 105 { 106 lock->owner = NULL; 107 raw_spin_lock_init(&lock->wait_lock); 108 lock->waiters = RB_ROOT_CACHED; 109 } 110 111 /* 112 * PI-futex support (proxy locking functions, etc.): 113 */ 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); 129 130 extern int rt_mutex_futex_trylock(struct rt_mutex *l); 131 extern int __rt_mutex_futex_trylock(struct rt_mutex *l); 132 133 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); 136 137 extern void rt_mutex_postunlock(struct wake_q_head *wake_q); 138 139 /* Debug functions */ 140 static inline void debug_rt_mutex_unlock(struct rt_mutex *lock) 141 { 142 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) 143 DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current); 144 } 145 146 static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock) 147 { 148 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) 149 DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock)); 150 } 151 152 static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter) 153 { 154 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) 155 memset(waiter, 0x11, sizeof(*waiter)); 156 } 157 158 static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter) 159 { 160 if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) 161 memset(waiter, 0x22, sizeof(*waiter)); 162 } 163 164 #endif 165