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/* SPDX-License-Identifier: GPL-2.0 */
/*
* RT Mutexes: blocking mutual exclusion locks with PI support
*
* started by Ingo Molnar and Thomas Gleixner:
*
* Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
* Copyright (C) 2006, Timesys Corp., Thomas Gleixner <tglx@timesys.com>
*
* This file contains the private data structure and API definitions.
*/
#ifndef __KERNEL_RTMUTEX_COMMON_H
#define __KERNEL_RTMUTEX_COMMON_H
#include <linux/debug_locks.h>
#include <linux/rtmutex.h>
#include <linux/sched/wake_q.h>
/*
* This is the control structure for tasks blocked on a rt_mutex,
* which is allocated on the kernel stack on of the blocked task.
*
* @tree_entry: pi node to enqueue into the mutex waiters tree
* @pi_tree_entry: pi node to enqueue into the mutex owner waiters tree
* @task: task reference to the blocked task
* @lock: Pointer to the rt_mutex on which the waiter blocks
* @wake_state: Wakeup state to use (TASK_NORMAL or TASK_RTLOCK_WAIT)
* @prio: Priority of the waiter
* @deadline: Deadline of the waiter if applicable
* @ww_ctx: WW context pointer
*/
struct rt_mutex_waiter {
struct rb_node tree_entry;
struct rb_node pi_tree_entry;
struct task_struct *task;
struct rt_mutex_base *lock;
unsigned int wake_state;
int prio;
u64 deadline;
struct ww_acquire_ctx *ww_ctx;
};
/**
* rt_wake_q_head - Wrapper around regular wake_q_head to support
* "sleeping" spinlocks on RT
* @head: The regular wake_q_head for sleeping lock variants
* @rtlock_task: Task pointer for RT lock (spin/rwlock) wakeups
*/
struct rt_wake_q_head {
struct wake_q_head head;
struct task_struct *rtlock_task;
};
#define DEFINE_RT_WAKE_Q(name) \
struct rt_wake_q_head name = { \
.head = WAKE_Q_HEAD_INITIALIZER(name.head), \
.rtlock_task = NULL, \
}
/*
* PI-futex support (proxy locking functions, etc.):
*/
extern void rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
struct task_struct *proxy_owner);
extern void rt_mutex_proxy_unlock(struct rt_mutex_base *lock);
extern int __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
struct rt_mutex_waiter *waiter,
struct task_struct *task);
extern int rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
struct rt_mutex_waiter *waiter,
struct task_struct *task);
extern int rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
struct hrtimer_sleeper *to,
struct rt_mutex_waiter *waiter);
extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
struct rt_mutex_waiter *waiter);
extern int rt_mutex_futex_trylock(struct rt_mutex_base *l);
extern int __rt_mutex_futex_trylock(struct rt_mutex_base *l);
extern void rt_mutex_futex_unlock(struct rt_mutex_base *lock);
extern bool __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
struct rt_wake_q_head *wqh);
extern void rt_mutex_postunlock(struct rt_wake_q_head *wqh);
/*
* Must be guarded because this header is included from rcu/tree_plugin.h
* unconditionally.
*/
#ifdef CONFIG_RT_MUTEXES
static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock)
{
return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
}
/*
* Lockless speculative check whether @waiter is still the top waiter on
* @lock. This is solely comparing pointers and not derefencing the
* leftmost entry which might be about to vanish.
*/
static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock,
struct rt_mutex_waiter *waiter)
{
struct rb_node *leftmost = rb_first_cached(&lock->waiters);
return rb_entry(leftmost, struct rt_mutex_waiter, tree_entry) == waiter;
}
static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock)
{
struct rb_node *leftmost = rb_first_cached(&lock->waiters);
struct rt_mutex_waiter *w = NULL;
if (leftmost) {
w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
BUG_ON(w->lock != lock);
}
return w;
}
static inline int task_has_pi_waiters(struct task_struct *p)
{
return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
}
static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
{
return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter,
pi_tree_entry);
}
#define RT_MUTEX_HAS_WAITERS 1UL
static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
{
unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
}
/*
* Constants for rt mutex functions which have a selectable deadlock
* detection.
*
* RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are
* no further PI adjustments to be made.
*
* RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full
* walk of the lock chain.
*/
enum rtmutex_chainwalk {
RT_MUTEX_MIN_CHAINWALK,
RT_MUTEX_FULL_CHAINWALK,
};
static inline void __rt_mutex_base_init(struct rt_mutex_base *lock)
{
raw_spin_lock_init(&lock->wait_lock);
lock->waiters = RB_ROOT_CACHED;
lock->owner = NULL;
}
/* Debug functions */
static inline void debug_rt_mutex_unlock(struct rt_mutex_base *lock)
{
if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
}
static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
{
if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
}
static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
{
if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
memset(waiter, 0x11, sizeof(*waiter));
}
static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
{
if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES))
memset(waiter, 0x22, sizeof(*waiter));
}
static inline void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
{
debug_rt_mutex_init_waiter(waiter);
RB_CLEAR_NODE(&waiter->pi_tree_entry);
RB_CLEAR_NODE(&waiter->tree_entry);
waiter->wake_state = TASK_NORMAL;
waiter->task = NULL;
}
static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter)
{
rt_mutex_init_waiter(waiter);
waiter->wake_state = TASK_RTLOCK_WAIT;
}
#else /* CONFIG_RT_MUTEXES */
/* Used in rcu/tree_plugin.h */
static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
{
return NULL;
}
#endif /* !CONFIG_RT_MUTEXES */
#endif
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