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