kernel/locking/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  */
  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