// SPDX-License-Identifier: GPL-2.0-only
/*
 * rtmutex API
 */
#include <linux/spinlock.h>
#include <linux/export.h>

#define RT_MUTEX_BUILD_MUTEX
#include "rtmutex.c"

/*
 * Max number of times we'll walk the boosting chain:
 */
int max_lock_depth = 1024;

static const struct ctl_table rtmutex_sysctl_table[] = {
        {
                .procname       = "max_lock_depth",
                .data           = &max_lock_depth,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
};

static int __init init_rtmutex_sysctl(void)
{
        register_sysctl_init("kernel", rtmutex_sysctl_table);
        return 0;
}

subsys_initcall(init_rtmutex_sysctl);

/*
 * Debug aware fast / slowpath lock,trylock,unlock
 *
 * The atomic acquire/release ops are compiled away, when either the
 * architecture does not support cmpxchg or when debugging is enabled.
 */
static __always_inline int __rt_mutex_lock_common(struct rt_mutex *lock,
                                                  unsigned int state,
                                                  struct lockdep_map *nest_lock,
                                                  unsigned int subclass)
{
        int ret;

        might_sleep();
        mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, _RET_IP_);
        ret = __rt_mutex_lock(&lock->rtmutex, state);
        if (ret)
                mutex_release(&lock->dep_map, _RET_IP_);
        return ret;
}

void rt_mutex_base_init(struct rt_mutex_base *rtb)
{
        __rt_mutex_base_init(rtb);
}
EXPORT_SYMBOL(rt_mutex_base_init);

#ifdef CONFIG_DEBUG_LOCK_ALLOC
/**
 * rt_mutex_lock_nested - lock a rt_mutex
 *
 * @lock: the rt_mutex to be locked
 * @subclass: the lockdep subclass
 */
void __sched rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int subclass)
{
        __rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, NULL, subclass);
}
EXPORT_SYMBOL_GPL(rt_mutex_lock_nested);

void __sched _rt_mutex_lock_nest_lock(struct rt_mutex *lock, struct lockdep_map *nest_lock)
{
        __rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, nest_lock, 0);
}
EXPORT_SYMBOL_GPL(_rt_mutex_lock_nest_lock);

#else /* !CONFIG_DEBUG_LOCK_ALLOC */

/**
 * rt_mutex_lock - lock a rt_mutex
 *
 * @lock: the rt_mutex to be locked
 */
void __sched rt_mutex_lock(struct rt_mutex *lock)
{
        __rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, NULL, 0);
}
EXPORT_SYMBOL_GPL(rt_mutex_lock);
#endif

/**
 * rt_mutex_lock_interruptible - lock a rt_mutex interruptible
 *
 * @lock:               the rt_mutex to be locked
 *
 * Returns:
 *  0           on success
 * -EINTR       when interrupted by a signal
 */
int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock)
{
        return __rt_mutex_lock_common(lock, TASK_INTERRUPTIBLE, NULL, 0);
}
EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);

/**
 * rt_mutex_lock_killable - lock a rt_mutex killable
 *
 * @lock:               the rt_mutex to be locked
 *
 * Returns:
 *  0           on success
 * -EINTR       when interrupted by a signal
 */
int __sched rt_mutex_lock_killable(struct rt_mutex *lock)
{
        return __rt_mutex_lock_common(lock, TASK_KILLABLE, NULL, 0);
}
EXPORT_SYMBOL_GPL(rt_mutex_lock_killable);

/**
 * rt_mutex_trylock - try to lock a rt_mutex
 *
 * @lock:       the rt_mutex to be locked
 *
 * This function can only be called in thread context. It's safe to call it
 * from atomic regions, but not from hard or soft interrupt context.
 *
 * Returns:
 *  1 on success
 *  0 on contention
 */
int __sched rt_mutex_trylock(struct rt_mutex *lock)
{
        int ret;

        if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES) && WARN_ON_ONCE(!in_task()))
                return 0;

        ret = __rt_mutex_trylock(&lock->rtmutex);
        if (ret)
                mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);

        return ret;
}
EXPORT_SYMBOL_GPL(rt_mutex_trylock);

/**
 * rt_mutex_unlock - unlock a rt_mutex
 *
 * @lock: the rt_mutex to be unlocked
 */
void __sched rt_mutex_unlock(struct rt_mutex *lock)
{
        mutex_release(&lock->dep_map, _RET_IP_);
        __rt_mutex_unlock(&lock->rtmutex);
}
EXPORT_SYMBOL_GPL(rt_mutex_unlock);

/*
 * Futex variants, must not use fastpath.
 */
int __sched rt_mutex_futex_trylock(struct rt_mutex_base *lock)
{
        return rt_mutex_slowtrylock(lock);
}

int __sched __rt_mutex_futex_trylock(struct rt_mutex_base *lock)
{
        return __rt_mutex_slowtrylock(lock);
}

/**
 * __rt_mutex_futex_unlock - Futex variant, that since futex variants
 * do not use the fast-path, can be simple and will not need to retry.
 *
 * @lock:       The rt_mutex to be unlocked
 * @wqh:        The wake queue head from which to get the next lock waiter
 */
bool __sched __rt_mutex_futex_unlock(struct rt_mutex_base *lock,
                                     struct rt_wake_q_head *wqh)
{
        lockdep_assert_held(&lock->wait_lock);

        debug_rt_mutex_unlock(lock);

        if (!rt_mutex_has_waiters(lock)) {
                lock->owner = NULL;
                return false; /* done */
        }

        /*
         * mark_wakeup_next_waiter() deboosts and retains preemption
         * disabled when dropping the wait_lock, to avoid inversion prior
         * to the wakeup.  preempt_disable() therein pairs with the
         * preempt_enable() in rt_mutex_postunlock().
         */
        mark_wakeup_next_waiter(wqh, lock);

        return true; /* call postunlock() */
}

void __sched rt_mutex_futex_unlock(struct rt_mutex_base *lock)
{
        DEFINE_RT_WAKE_Q(wqh);
        unsigned long flags;
        bool postunlock;

        raw_spin_lock_irqsave(&lock->wait_lock, flags);
        postunlock = __rt_mutex_futex_unlock(lock, &wqh);
        raw_spin_unlock_irqrestore(&lock->wait_lock, flags);

        if (postunlock)
                rt_mutex_postunlock(&wqh);
}

/**
 * __rt_mutex_init - initialize the rt_mutex
 *
 * @lock:       The rt_mutex to be initialized
 * @name:       The lock name used for debugging
 * @key:        The lock class key used for debugging
 *
 * Initialize the rt_mutex to unlocked state.
 *
 * Initializing of a locked rt_mutex is not allowed
 */
void __sched __rt_mutex_init(struct rt_mutex *lock, const char *name,
                             struct lock_class_key *key)
{
        debug_check_no_locks_freed((void *)lock, sizeof(*lock));
        __rt_mutex_base_init(&lock->rtmutex);
        lockdep_init_map_wait(&lock->dep_map, name, key, 0, LD_WAIT_SLEEP);
}
EXPORT_SYMBOL_GPL(__rt_mutex_init);

/**
 * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
 *                              proxy owner
 *
 * @lock:       the rt_mutex to be locked
 * @proxy_owner:the task to set as owner
 *
 * No locking. Caller has to do serializing itself
 *
 * Special API call for PI-futex support. This initializes the rtmutex and
 * assigns it to @proxy_owner. Concurrent operations on the rtmutex are not
 * possible at this point because the pi_state which contains the rtmutex
 * is not yet visible to other tasks.
 */
void __sched rt_mutex_init_proxy_locked(struct rt_mutex_base *lock,
                                        struct task_struct *proxy_owner)
{
        static struct lock_class_key pi_futex_key;

        __rt_mutex_base_init(lock);
        /*
         * On PREEMPT_RT the futex hashbucket spinlock becomes 'sleeping'
         * and rtmutex based. That causes a lockdep false positive, because
         * some of the futex functions invoke spin_unlock(&hb->lock) with
         * the wait_lock of the rtmutex associated to the pi_futex held.
         * spin_unlock() in turn takes wait_lock of the rtmutex on which
         * the spinlock is based, which makes lockdep notice a lock
         * recursion. Give the futex/rtmutex wait_lock a separate key.
         */
        lockdep_set_class(&lock->wait_lock, &pi_futex_key);
        rt_mutex_set_owner(lock, proxy_owner);
}

/**
 * rt_mutex_proxy_unlock - release a lock on behalf of owner
 *
 * @lock:       the rt_mutex to be locked
 *
 * No locking. Caller has to do serializing itself
 *
 * Special API call for PI-futex support. This just cleans up the rtmutex
 * (debugging) state. Concurrent operations on this rt_mutex are not
 * possible because it belongs to the pi_state which is about to be freed
 * and it is not longer visible to other tasks.
 */
void __sched rt_mutex_proxy_unlock(struct rt_mutex_base *lock)
{
        debug_rt_mutex_proxy_unlock(lock);
        rt_mutex_clear_owner(lock);
}

/**
 * __rt_mutex_start_proxy_lock() - Start lock acquisition for another task
 * @lock:               the rt_mutex to take
 * @waiter:             the pre-initialized rt_mutex_waiter
 * @task:               the task to prepare
 * @wake_q:             the wake_q to wake tasks after we release the wait_lock
 *
 * Starts the rt_mutex acquire; it enqueues the @waiter and does deadlock
 * detection. It does not wait, see rt_mutex_wait_proxy_lock() for that.
 *
 * NOTE: does _NOT_ remove the @waiter on failure; must either call
 * rt_mutex_wait_proxy_lock() or rt_mutex_cleanup_proxy_lock() after this.
 *
 * Returns:
 *  0 - task blocked on lock
 *  1 - acquired the lock for task, caller should wake it up
 * <0 - error
 *
 * Special API call for PI-futex support.
 */
int __sched __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
                                        struct rt_mutex_waiter *waiter,
                                        struct task_struct *task,
                                        struct wake_q_head *wake_q)
{
        int ret;

        lockdep_assert_held(&lock->wait_lock);

        if (try_to_take_rt_mutex(lock, task, NULL))
                return 1;

        /* We enforce deadlock detection for futexes */
        ret = task_blocks_on_rt_mutex(lock, waiter, task, NULL,
                                      RT_MUTEX_FULL_CHAINWALK, wake_q);

        if (ret && !rt_mutex_owner(lock)) {
                /*
                 * Reset the return value. We might have
                 * returned with -EDEADLK and the owner
                 * released the lock while we were walking the
                 * pi chain.  Let the waiter sort it out.
                 */
                ret = 0;
        }

        return ret;
}

/**
 * rt_mutex_start_proxy_lock() - Start lock acquisition for another task
 * @lock:               the rt_mutex to take
 * @waiter:             the pre-initialized rt_mutex_waiter
 * @task:               the task to prepare
 *
 * Starts the rt_mutex acquire; it enqueues the @waiter and does deadlock
 * detection. It does not wait, see rt_mutex_wait_proxy_lock() for that.
 *
 * NOTE: unlike __rt_mutex_start_proxy_lock this _DOES_ remove the @waiter
 * on failure.
 *
 * Returns:
 *  0 - task blocked on lock
 *  1 - acquired the lock for task, caller should wake it up
 * <0 - error
 *
 * Special API call for PI-futex support.
 */
int __sched rt_mutex_start_proxy_lock(struct rt_mutex_base *lock,
                                      struct rt_mutex_waiter *waiter,
                                      struct task_struct *task)
{
        int ret;
        DEFINE_WAKE_Q(wake_q);

        raw_spin_lock_irq(&lock->wait_lock);
        ret = __rt_mutex_start_proxy_lock(lock, waiter, task, &wake_q);
        if (unlikely(ret))
                remove_waiter(lock, waiter);
        preempt_disable();
        raw_spin_unlock_irq(&lock->wait_lock);
        wake_up_q(&wake_q);
        preempt_enable();

        return ret;
}

/**
 * rt_mutex_wait_proxy_lock() - Wait for lock acquisition
 * @lock:               the rt_mutex we were woken on
 * @to:                 the timeout, null if none. hrtimer should already have
 *                      been started.
 * @waiter:             the pre-initialized rt_mutex_waiter
 *
 * Wait for the lock acquisition started on our behalf by
 * rt_mutex_start_proxy_lock(). Upon failure, the caller must call
 * rt_mutex_cleanup_proxy_lock().
 *
 * Returns:
 *  0 - success
 * <0 - error, one of -EINTR, -ETIMEDOUT
 *
 * Special API call for PI-futex support
 */
int __sched rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
                                     struct hrtimer_sleeper *to,
                                     struct rt_mutex_waiter *waiter)
{
        int ret;

        raw_spin_lock_irq(&lock->wait_lock);
        /* sleep on the mutex */
        set_current_state(TASK_INTERRUPTIBLE);
        ret = rt_mutex_slowlock_block(lock, NULL, TASK_INTERRUPTIBLE, to, waiter, NULL);
        /*
         * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
         * have to fix that up.
         */
        fixup_rt_mutex_waiters(lock, true);
        raw_spin_unlock_irq(&lock->wait_lock);

        return ret;
}

/**
 * rt_mutex_cleanup_proxy_lock() - Cleanup failed lock acquisition
 * @lock:               the rt_mutex we were woken on
 * @waiter:             the pre-initialized rt_mutex_waiter
 *
 * Attempt to clean up after a failed __rt_mutex_start_proxy_lock() or
 * rt_mutex_wait_proxy_lock().
 *
 * Unless we acquired the lock; we're still enqueued on the wait-list and can
 * in fact still be granted ownership until we're removed. Therefore we can
 * find we are in fact the owner and must disregard the
 * rt_mutex_wait_proxy_lock() failure.
 *
 * Returns:
 *  true  - did the cleanup, we done.
 *  false - we acquired the lock after rt_mutex_wait_proxy_lock() returned,
 *          caller should disregards its return value.
 *
 * Special API call for PI-futex support
 */
bool __sched rt_mutex_cleanup_proxy_lock(struct rt_mutex_base *lock,
                                         struct rt_mutex_waiter *waiter)
{
        bool cleanup = false;

        raw_spin_lock_irq(&lock->wait_lock);
        /*
         * Do an unconditional try-lock, this deals with the lock stealing
         * state where __rt_mutex_futex_unlock() -> mark_wakeup_next_waiter()
         * sets a NULL owner.
         *
         * We're not interested in the return value, because the subsequent
         * test on rt_mutex_owner() will infer that. If the trylock succeeded,
         * we will own the lock and it will have removed the waiter. If we
         * failed the trylock, we're still not owner and we need to remove
         * ourselves.
         */
        try_to_take_rt_mutex(lock, current, waiter);
        /*
         * Unless we're the owner; we're still enqueued on the wait_list.
         * So check if we became owner, if not, take us off the wait_list.
         */
        if (rt_mutex_owner(lock) != current) {
                remove_waiter(lock, waiter);
                cleanup = true;
        }
        /*
         * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
         * have to fix that up.
         */
        fixup_rt_mutex_waiters(lock, false);

        raw_spin_unlock_irq(&lock->wait_lock);

        return cleanup;
}

/*
 * Recheck the pi chain, in case we got a priority setting
 *
 * Called from sched_setscheduler
 */
void __sched rt_mutex_adjust_pi(struct task_struct *task)
{
        struct rt_mutex_waiter *waiter;
        struct rt_mutex_base *next_lock;
        unsigned long flags;

        raw_spin_lock_irqsave(&task->pi_lock, flags);

        waiter = task->pi_blocked_on;
        if (!waiter || rt_waiter_node_equal(&waiter->tree, task_to_waiter_node(task))) {
                raw_spin_unlock_irqrestore(&task->pi_lock, flags);
                return;
        }
        next_lock = waiter->lock;
        raw_spin_unlock_irqrestore(&task->pi_lock, flags);

        /* gets dropped in rt_mutex_adjust_prio_chain()! */
        get_task_struct(task);

        rt_mutex_adjust_prio_chain(task, RT_MUTEX_MIN_CHAINWALK, NULL,
                                   next_lock, NULL, task);
}

/*
 * Performs the wakeup of the top-waiter and re-enables preemption.
 */
void __sched rt_mutex_postunlock(struct rt_wake_q_head *wqh)
{
        rt_mutex_wake_up_q(wqh);
}

#ifdef CONFIG_DEBUG_RT_MUTEXES
void rt_mutex_debug_task_free(struct task_struct *task)
{
        DEBUG_LOCKS_WARN_ON(!RB_EMPTY_ROOT(&task->pi_waiters.rb_root));
        DEBUG_LOCKS_WARN_ON(task->pi_blocked_on);
}
#endif

#ifdef CONFIG_PREEMPT_RT
/* Mutexes */
static void __mutex_rt_init_generic(struct mutex *mutex)
{
        rt_mutex_base_init(&mutex->rtmutex);
        debug_check_no_locks_freed((void *)mutex, sizeof(*mutex));
}

static __always_inline int __mutex_lock_common(struct mutex *lock,
                                               unsigned int state,
                                               unsigned int subclass,
                                               struct lockdep_map *nest_lock,
                                               unsigned long ip)
{
        int ret;

        might_sleep();
        mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
        ret = __rt_mutex_lock(&lock->rtmutex, state);
        if (ret)
                mutex_release(&lock->dep_map, ip);
        else
                lock_acquired(&lock->dep_map, ip);
        return ret;
}

#ifdef CONFIG_DEBUG_LOCK_ALLOC
void mutex_rt_init_lockdep(struct mutex *mutex, const char *name, struct lock_class_key *key)
{
        __mutex_rt_init_generic(mutex);
        lockdep_init_map_wait(&mutex->dep_map, name, key, 0, LD_WAIT_SLEEP);
}
EXPORT_SYMBOL(mutex_rt_init_lockdep);

void __sched mutex_lock_nested(struct mutex *lock, unsigned int subclass)
{
        __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
}
EXPORT_SYMBOL_GPL(mutex_lock_nested);

void __sched _mutex_lock_nest_lock(struct mutex *lock,
                                   struct lockdep_map *nest_lock)
{
        __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, nest_lock, _RET_IP_);
}
EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);

int __sched mutex_lock_interruptible_nested(struct mutex *lock,
                                            unsigned int subclass)
{
        return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, subclass, NULL, _RET_IP_);
}
EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);

int __sched _mutex_lock_killable(struct mutex *lock, unsigned int subclass,
                                 struct lockdep_map *nest_lock)
{
        return __mutex_lock_common(lock, TASK_KILLABLE, subclass, nest_lock, _RET_IP_);
}
EXPORT_SYMBOL_GPL(_mutex_lock_killable);

void __sched mutex_lock_io_nested(struct mutex *lock, unsigned int subclass)
{
        int token;

        might_sleep();

        token = io_schedule_prepare();
        __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
        io_schedule_finish(token);
}
EXPORT_SYMBOL_GPL(mutex_lock_io_nested);

int __sched _mutex_trylock_nest_lock(struct mutex *lock,
                                     struct lockdep_map *nest_lock)
{
        int ret;

        if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES) && WARN_ON_ONCE(!in_task()))
                return 0;

        ret = __rt_mutex_trylock(&lock->rtmutex);
        if (ret)
                mutex_acquire_nest(&lock->dep_map, 0, 1, nest_lock, _RET_IP_);

        return ret;
}
EXPORT_SYMBOL_GPL(_mutex_trylock_nest_lock);
#else /* CONFIG_DEBUG_LOCK_ALLOC */

void mutex_rt_init_generic(struct mutex *mutex)
{
        __mutex_rt_init_generic(mutex);
}
EXPORT_SYMBOL(mutex_rt_init_generic);

void __sched mutex_lock(struct mutex *lock)
{
        __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
}
EXPORT_SYMBOL(mutex_lock);

int __sched mutex_lock_interruptible(struct mutex *lock)
{
        return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_);
}
EXPORT_SYMBOL(mutex_lock_interruptible);

int __sched mutex_lock_killable(struct mutex *lock)
{
        return __mutex_lock_common(lock, TASK_KILLABLE, 0, NULL, _RET_IP_);
}
EXPORT_SYMBOL(mutex_lock_killable);

void __sched mutex_lock_io(struct mutex *lock)
{
        int token = io_schedule_prepare();

        __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
        io_schedule_finish(token);
}
EXPORT_SYMBOL(mutex_lock_io);

int __sched mutex_trylock(struct mutex *lock)
{
        if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES) && WARN_ON_ONCE(!in_task()))
                return 0;

        return __rt_mutex_trylock(&lock->rtmutex);
}
EXPORT_SYMBOL(mutex_trylock);
#endif /* !CONFIG_DEBUG_LOCK_ALLOC */

void __sched mutex_unlock(struct mutex *lock)
{
        mutex_release(&lock->dep_map, _RET_IP_);
        __rt_mutex_unlock(&lock->rtmutex);
}
EXPORT_SYMBOL(mutex_unlock);

#endif /* CONFIG_PREEMPT_RT */