| 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 | * 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 | extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock); |
| 84 | extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock, |
| 85 | struct rt_mutex_waiter *waiter, |
| 86 | struct task_struct *task); |
| 87 | extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock, |
| 88 | struct rt_mutex_waiter *waiter, |
| 89 | struct task_struct *task); |
| 90 | extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock, |
| 91 | struct hrtimer_sleeper *to, |
| 92 | struct rt_mutex_waiter *waiter); |
| 93 | extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock, |
| 94 | struct rt_mutex_waiter *waiter); |
| 95 | |
| 96 | extern int rt_mutex_futex_trylock(struct rt_mutex_base *l); |
| 97 | extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l); |
| 98 | |
| 99 | extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock); |
| 100 | extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock, |
| 101 | struct rt_wake_q_head *wqh); |
| 102 | |
| 103 | extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh); |
| 104 | |
| 105 | /* |
| 106 | * Must be guarded because this header is included from rcu/tree_plugin.h |
| 107 | * unconditionally. |
| 108 | */ |
| 109 | #ifdef CONFIG_RT_MUTEXES |
| 110 | static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock) |
| 111 | { |
| 112 | return !RB_EMPTY_ROOT(&lock->waiters.rb_root); |
| 113 | } |
| 114 | |
| 115 | /* |
| 116 | * Lockless speculative check whether @waiter is still the top waiter on |
| 117 | * @lock. This is solely comparing pointers and not derefencing the |
| 118 | * leftmost entry which might be about to vanish. |
| 119 | */ |
| 120 | static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock, |
| 121 | struct rt_mutex_waiter *waiter) |
| 122 | { |
| 123 | struct rb_node *leftmost = rb_first_cached(&lock->waiters); |
| 124 | |
| 125 | return rb_entry(leftmost, struct rt_mutex_waiter, tree.entry) == waiter; |
| 126 | } |
| 127 | |
| 128 | static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock) |
| 129 | { |
| 130 | struct rb_node *leftmost = rb_first_cached(&lock->waiters); |
| 131 | struct rt_mutex_waiter *w = NULL; |
| 132 | |
| 133 | lockdep_assert_held(&lock->wait_lock); |
| 134 | |
| 135 | if (leftmost) { |
| 136 | w = rb_entry(leftmost, struct rt_mutex_waiter, tree.entry); |
| 137 | BUG_ON(w->lock != lock); |
| 138 | } |
| 139 | return w; |
| 140 | } |
| 141 | |
| 142 | static inline int task_has_pi_waiters(struct task_struct *p) |
| 143 | { |
| 144 | return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root); |
| 145 | } |
| 146 | |
| 147 | static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p) |
| 148 | { |
| 149 | lockdep_assert_held(&p->pi_lock); |
| 150 | |
| 151 | return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter, |
| 152 | pi_tree.entry); |
| 153 | } |
| 154 | |
| 155 | #define RT_MUTEX_HAS_WAITERS 1UL |
| 156 | |
| 157 | static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock) |
| 158 | { |
| 159 | unsigned long owner = (unsigned long) READ_ONCE(lock->owner); |
| 160 | |
| 161 | return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS); |
| 162 | } |
| 163 | |
| 164 | /* |
| 165 | * Constants for rt mutex functions which have a selectable deadlock |
| 166 | * detection. |
| 167 | * |
| 168 | * RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are |
| 169 | * no further PI adjustments to be made. |
| 170 | * |
| 171 | * RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full |
| 172 | * walk of the lock chain. |
| 173 | */ |
| 174 | enum rtmutex_chainwalk { |
| 175 | RT_MUTEX_MIN_CHAINWALK, |
| 176 | RT_MUTEX_FULL_CHAINWALK, |
| 177 | }; |
| 178 | |
| 179 | static inline void __rt_mutex_base_init(struct rt_mutex_base *lock) |
| 180 | { |
| 181 | raw_spin_lock_init(&lock->wait_lock); |
| 182 | lock->waiters = RB_ROOT_CACHED; |
| 183 | lock->owner = NULL; |
| 184 | } |
| 185 | |
| 186 | /* Debug functions */ |
| 187 | static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock) |
| 188 | { |
| 189 | if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) |
| 190 | DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current); |
| 191 | } |
| 192 | |
| 193 | static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock) |
| 194 | { |
| 195 | if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) |
| 196 | DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock)); |
| 197 | } |
| 198 | |
| 199 | static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter) |
| 200 | { |
| 201 | if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) |
| 202 | memset(waiter, 0x11, sizeof(*waiter)); |
| 203 | } |
| 204 | |
| 205 | static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter) |
| 206 | { |
| 207 | if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) |
| 208 | memset(waiter, 0x22, sizeof(*waiter)); |
| 209 | } |
| 210 | |
| 211 | static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter) |
| 212 | { |
| 213 | debug_rt_mutex_init_waiter(waiter); |
| 214 | RB_CLEAR_NODE(&waiter->pi_tree.entry); |
| 215 | RB_CLEAR_NODE(&waiter->tree.entry); |
| 216 | waiter->wake_state = TASK_NORMAL; |
| 217 | waiter->task = NULL; |
| 218 | } |
| 219 | |
| 220 | static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter) |
| 221 | { |
| 222 | rt_mutex_init_waiter(waiter); |
| 223 | waiter->wake_state = TASK_RTLOCK_WAIT; |
| 224 | } |
| 225 | |
| 226 | #else /* CONFIG_RT_MUTEXES */ |
| 227 | /* Used in rcu/tree_plugin.h */ |
| 228 | static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock) |
| 229 | { |
| 230 | return NULL; |
| 231 | } |
| 232 | #endif /* !CONFIG_RT_MUTEXES */ |
| 233 | |
| 234 | #endif |