Line data    Source code

       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             :  * @wake_state:         Wakeup state to use (TASK_NORMAL or TASK_RTLOCK_WAIT)
      29             :  * @prio:               Priority of the waiter
      30             :  * @deadline:           Deadline of the waiter if applicable
      31             :  * @ww_ctx:             WW context pointer
      32             :  */
      33             : struct rt_mutex_waiter {
      34             :         struct rb_node          tree_entry;
      35             :         struct rb_node          pi_tree_entry;
      36             :         struct task_struct      *task;
      37             :         struct rt_mutex_base    *lock;
      38             :         unsigned int            wake_state;
      39             :         int                     prio;
      40             :         u64                     deadline;
      41             :         struct ww_acquire_ctx   *ww_ctx;
      42             : };
      43             : 
      44             : /**
      45             :  * rt_wake_q_head - Wrapper around regular wake_q_head to support
      46             :  *                  "sleeping" spinlocks on RT
      47             :  * @head:               The regular wake_q_head for sleeping lock variants
      48             :  * @rtlock_task:        Task pointer for RT lock (spin/rwlock) wakeups
      49             :  */
      50             : struct rt_wake_q_head {
      51             :         struct wake_q_head      head;
      52             :         struct task_struct      *rtlock_task;
      53             : };
      54             : 
      55             : #define DEFINE_RT_WAKE_Q(name)                                          \
      56             :         struct rt_wake_q_head name = {                                  \
      57             :                 .head           = WAKE_Q_HEAD_INITIALIZER(name.head),   \
      58             :                 .rtlock_task    = NULL,                                 \
      59             :         }
      60             : 
      61             : /*
      62             :  * PI-futex support (proxy locking functions, etc.):
      63             :  */
      64             : extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
      65             :                                        struct task_struct *proxy_owner);
      66             : extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock);
      67             : extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
      68             :                                      struct rt_mutex_waiter *waiter,
      69             :                                      struct task_struct *task);
      70             : extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
      71             :                                      struct rt_mutex_waiter *waiter,
      72             :                                      struct task_struct *task);
      73             : extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
      74             :                                struct hrtimer_sleeper *to,
      75             :                                struct rt_mutex_waiter *waiter);
      76             : extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
      77             :                                  struct rt_mutex_waiter *waiter);
      78             : 
      79             : extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
      80             : extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
      81             : 
      82             : extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
      83             : extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
      84             :                                 struct rt_wake_q_head *wqh);
      85             : 
      86             : extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh);
      87             : 
      88             : /*
      89             :  * Must be guarded because this header is included from rcu/tree_plugin.h
      90             :  * unconditionally.
      91             :  */
      92             : #ifdef CONFIG_RT_MUTEXES
      93             : static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
      94             : {
      95           0 :         return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
      96             : }
      97             : 
      98             : /*
      99             :  * Lockless speculative check whether @waiter is still the top waiter on
     100             :  * @lock. This is solely comparing pointers and not derefencing the
     101             :  * leftmost entry which might be about to vanish.
     102             :  */
     103             : static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock,
     104             :                                                  struct rt_mutex_waiter *waiter)
     105             : {
     106             :         struct rb_node *leftmost = rb_first_cached(&lock->waiters);
     107             : 
     108             :         return rb_entry(leftmost, struct rt_mutex_waiter, tree_entry) == waiter;
     109             : }
     110             : 
     111           0 : static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
     112             : {
     113           0 :         struct rb_node *leftmost = rb_first_cached(&lock->waiters);
     114           0 :         struct rt_mutex_waiter *w = NULL;
     115             : 
     116           0 :         if (leftmost) {
     117           0 :                 w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
     118           0 :                 BUG_ON(w->lock != lock);
     119             :         }
     120           0 :         return w;
     121             : }
     122             : 
     123             : static inline int task_has_pi_waiters(struct task_struct *p)
     124             : {
     125           0 :         return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
     126             : }
     127             : 
     128             : static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
     129             : {
     130           0 :         return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
     131             :                         pi_tree_entry);
     132             : }
     133             : 
     134             : #define RT_MUTEX_HAS_WAITERS    1UL
     135             : 
     136             : static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
     137             : {
     138           0 :         unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
     139             : 
     140           0 :         return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
     141             : }
     142             : 
     143             : /*
     144             :  * Constants for rt mutex functions which have a selectable deadlock
     145             :  * detection.
     146             :  *
     147             :  * RT_MUTEX_MIN_CHAINWALK:      Stops the lock chain walk when there are
     148             :  *                              no further PI adjustments to be made.
     149             :  *
     150             :  * RT_MUTEX_FULL_CHAINWALK:     Invoke deadlock detection with a full
     151             :  *                              walk of the lock chain.
     152             :  */
     153             : enum rtmutex_chainwalk {
     154             :         RT_MUTEX_MIN_CHAINWALK,
     155             :         RT_MUTEX_FULL_CHAINWALK,
     156             : };
     157             : 
     158             : static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
     159             : {
     160             :         raw_spin_lock_init(&lock->wait_lock);
     161           0 :         lock->waiters = RB_ROOT_CACHED;
     162           0 :         lock->owner = NULL;
     163             : }
     164             : 
     165             : /* Debug functions */
     166             : static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock)
     167             : {
     168             :         if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
     169             :                 DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
     170             : }
     171             : 
     172             : static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
     173             : {
     174             :         if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
     175             :                 DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
     176             : }
     177             : 
     178             : static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
     179             : {
     180             :         if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
     181             :                 memset(waiter, 0x11, sizeof(*waiter));
     182             : }
     183             : 
     184             : static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
     185             : {
     186             :         if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
     187             :                 memset(waiter, 0x22, sizeof(*waiter));
     188             : }
     189             : 
     190             : static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
     191             : {
     192           0 :         debug_rt_mutex_init_waiter(waiter);
     193           0 :         RB_CLEAR_NODE(&waiter->pi_tree_entry);
     194           0 :         RB_CLEAR_NODE(&waiter->tree_entry);
     195           0 :         waiter->wake_state = TASK_NORMAL;
     196           0 :         waiter->task = NULL;
     197             : }
     198             : 
     199             : static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter)
     200             : {
     201             :         rt_mutex_init_waiter(waiter);
     202             :         waiter->wake_state = TASK_RTLOCK_WAIT;
     203             : }
     204             : 
     205             : #else /* CONFIG_RT_MUTEXES */
     206             : /* Used in rcu/tree_plugin.h */
     207             : static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
     208             : {
     209             :         return NULL;
     210             : }
     211             : #endif  /* !CONFIG_RT_MUTEXES */
     212             : 
     213             : #endif