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/rtmutex.h>
  17 #include <linux/sched/wake_q.h>
  18
  19 /*
  20  * This is the control structure for tasks blocked on a rt_mutex,
  21  * which is allocated on the kernel stack on of the blocked task.
  22  *
  23  * @tree_entry:         pi node to enqueue into the mutex waiters tree
  24  * @pi_tree_entry:      pi node to enqueue into the mutex owner waiters tree
  25  * @task:               task reference to the blocked task
  26  */
  27 struct rt_mutex_waiter {
  28         struct rb_node          tree_entry;
  29         struct rb_node          pi_tree_entry;
  30         struct task_struct      *task;
  31         struct rt_mutex         *lock;
  32 #ifdef CONFIG_DEBUG_RT_MUTEXES
  33         unsigned long           ip;
  34         struct pid              *deadlock_task_pid;
  35         struct rt_mutex         *deadlock_lock;
  36 #endif
  37         int prio;
  38         u64 deadline;
  39 };
  40
  41 /*
  42  * Various helpers to access the waiters-tree:
  43  */
  44
  45 #ifdef CONFIG_RT_MUTEXES
  46
  47 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
  48 {
  49         return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
  50 }
  51
  52 static inline struct rt_mutex_waiter *
  53 rt_mutex_top_waiter(struct rt_mutex *lock)
  54 {
  55         struct rt_mutex_waiter *w;
  56
  57         w = rb_entry(lock->waiters.rb_leftmost,
  58                      struct rt_mutex_waiter, tree_entry);
  59         BUG_ON(w->lock != lock);
  60
  61         return w;
  62 }
  63
  64 static inline int task_has_pi_waiters(struct task_struct *p)
  65 {
  66         return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
  67 }
  68
  69 static inline struct rt_mutex_waiter *
  70 task_top_pi_waiter(struct task_struct *p)
  71 {
  72         return rb_entry(p->pi_waiters.rb_leftmost,
  73                         struct rt_mutex_waiter, pi_tree_entry);
  74 }
  75
  76 #else
  77
  78 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
  79 {
  80         return false;
  81 }
  82
  83 static inline struct rt_mutex_waiter *
  84 rt_mutex_top_waiter(struct rt_mutex *lock)
  85 {
  86         return NULL;
  87 }
  88
  89 static inline int task_has_pi_waiters(struct task_struct *p)
  90 {
  91         return false;
  92 }
  93
  94 static inline struct rt_mutex_waiter *
  95 task_top_pi_waiter(struct task_struct *p)
  96 {
  97         return NULL;
  98 }
  99
 100 #endif
 101
 102 /*
 103  * lock->owner state tracking:
 104  */
 105 #define RT_MUTEX_HAS_WAITERS    1UL
 106
 107 static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock)
 108 {
 109         unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
 110
 111         return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
 112 }
 113
 114 /*
 115  * Constants for rt mutex functions which have a selectable deadlock
 116  * detection.
 117  *
 118  * RT_MUTEX_MIN_CHAINWALK:      Stops the lock chain walk when there are
 119  *                              no further PI adjustments to be made.
 120  *
 121  * RT_MUTEX_FULL_CHAINWALK:     Invoke deadlock detection with a full
 122  *                              walk of the lock chain.
 123  */
 124 enum rtmutex_chainwalk {
 125         RT_MUTEX_MIN_CHAINWALK,
 126         RT_MUTEX_FULL_CHAINWALK,
 127 };
 128
 129 /*
 130  * PI-futex support (proxy locking functions, etc.):
 131  */
 132 extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock);
 133 extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
 134                                        struct task_struct *proxy_owner);
 135 extern void rt_mutex_proxy_unlock(struct rt_mutex *lock,
 136                                   struct task_struct *proxy_owner);
 137 extern void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter);
 138 extern int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
 139                                      struct rt_mutex_waiter *waiter,
 140                                      struct task_struct *task);
 141 extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
 142                                      struct rt_mutex_waiter *waiter,
 143                                      struct task_struct *task);
 144 extern int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
 145                                struct hrtimer_sleeper *to,
 146                                struct rt_mutex_waiter *waiter);
 147 extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
 148                                  struct rt_mutex_waiter *waiter);
 149
 150 extern int rt_mutex_futex_trylock(struct rt_mutex *l);
 151
 152 extern void rt_mutex_futex_unlock(struct rt_mutex *lock);
 153 extern bool __rt_mutex_futex_unlock(struct rt_mutex *lock,
 154                                  struct wake_q_head *wqh);
 155
 156 extern void rt_mutex_postunlock(struct wake_q_head *wake_q);
 157
 158 #ifdef CONFIG_DEBUG_RT_MUTEXES
 159 # include "rtmutex-debug.h"
 160 #else
 161 # include "rtmutex.h"
 162 #endif
 163
 164 #endif