rtmutex.c

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/*
 * RT-Mutexes: simple blocking mutual exclusion locks with PI support
 *
 * started by Ingo Molnar and Thomas Gleixner.
 *
 *  Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <[email protected]>
 *  Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <[email protected]>
 *  Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt
 *  Copyright (C) 2006 Esben Nielsen
 *
 *  See Documentation/rt-mutex-design.txt for details.
 */
#include <linux/spinlock.h>
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/timer.h>

#include "rtmutex_common.h"

/*
 * lock->owner state tracking:
 *
 * lock->owner holds the task_struct pointer of the owner. Bit 0
 * is used to keep track of the "lock has waiters" state.
 *
 * owner    bit0
 * NULL     0   lock is free (fast acquire possible)
 * NULL     1   lock is free and has waiters and the top waiter
 *              is going to take the lock*
 * taskpointer  0   lock is held (fast release possible)
 * taskpointer  1   lock is held and has waiters**
 *
 * The fast atomic compare exchange based acquire and release is only
 * possible when bit 0 of lock->owner is 0.
 *
 * (*) It also can be a transitional state when grabbing the lock
 * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock,
 * we need to set the bit0 before looking at the lock, and the owner may be
 * NULL in this small time, hence this can be a transitional state.
 *
 * (**) There is a small time when bit 0 is set but there are no
 * waiters. This can happen when grabbing the lock in the slow path.
 * To prevent a cmpxchg of the owner releasing the lock, we need to
 * set this bit before looking at the lock.
 */

static void
rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner)
{
    unsigned long val = (unsigned long)owner;

    if (rt_mutex_has_waiters(lock))
        val |= RT_MUTEX_HAS_WAITERS;

    lock->owner = (struct task_struct *)val;
}

static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)
{
    lock->owner = (struct task_struct *)
            ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS);
}

static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
{
    if (!rt_mutex_has_waiters(lock))
        clear_rt_mutex_waiters(lock);
}

/*
 * We can speed up the acquire/release, if the architecture
 * supports cmpxchg and if there's no debugging state to be set up
 */
#if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
# define rt_mutex_cmpxchg(l,c,n)    (cmpxchg(&l->owner, c, n) == c)
static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
{
    unsigned long owner, *p = (unsigned long *) &lock->owner;

    do {
        owner = *p;
    } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner);
}
#else
# define rt_mutex_cmpxchg(l,c,n)    (0)
static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
{
    lock->owner = (struct task_struct *)
            ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS);
}
#endif

/*
 * Calculate task priority from the waiter list priority
 *
 * Return task->normal_prio when the waiter list is empty or when
 * the waiter is not allowed to do priority boosting
 */
int rt_mutex_getprio(struct task_struct *task)
{
    if (likely(!task_has_pi_waiters(task)))
        return task->normal_prio;

    return min(task_top_pi_waiter(task)->pi_list_entry.prio,
           task->normal_prio);
}

/*
 * Adjust the priority of a task, after its pi_waiters got modified.
 *
 * This can be both boosting and unboosting. task->pi_lock must be held.
 */
static void __rt_mutex_adjust_prio(struct task_struct *task)
{
    int prio = rt_mutex_getprio(task);

    if (task->prio != prio)
        rt_mutex_setprio(task, prio);
}

/*
 * Adjust task priority (undo boosting). Called from the exit path of
 * rt_mutex_slowunlock() and rt_mutex_slowlock().
 *
 * (Note: We do this outside of the protection of lock->wait_lock to
 * allow the lock to be taken while or before we readjust the priority
 * of task. We do not use the spin_xx_mutex() variants here as we are
 * outside of the debug path.)
 */
static void rt_mutex_adjust_prio(struct task_struct *task)
{
    unsigned long flags;

    raw_spin_lock_irqsave(&task->pi_lock, flags);
    __rt_mutex_adjust_prio(task);
    raw_spin_unlock_irqrestore(&task->pi_lock, flags);
}

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

/*
 * Adjust the priority chain. Also used for deadlock detection.
 * Decreases task's usage by one - may thus free the task.
 * Returns 0 or -EDEADLK.
 */
static int rt_mutex_adjust_prio_chain(struct task_struct *task,
                      int deadlock_detect,
                      struct rt_mutex *orig_lock,
                      struct rt_mutex_waiter *orig_waiter,
                      struct task_struct *top_task)
{
    struct rt_mutex *lock;
    struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
    int detect_deadlock, ret = 0, depth = 0;
    unsigned long flags;

    detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
                             deadlock_detect);

    /*
     * The (de)boosting is a step by step approach with a lot of
     * pitfalls. We want this to be preemptible and we want hold a
     * maximum of two locks per step. So we have to check
     * carefully whether things change under us.
     */
 again:
    if (++depth > max_lock_depth) {
        static int prev_max;

        /*
         * Print this only once. If the admin changes the limit,
         * print a new message when reaching the limit again.
         */
        if (prev_max != max_lock_depth) {
            prev_max = max_lock_depth;
            printk(KERN_WARNING "Maximum lock depth %d reached "
                   "task: %s (%d)\n", max_lock_depth,
                   top_task->comm, task_pid_nr(top_task));
        }
        put_task_struct(task);

        return deadlock_detect ? -EDEADLK : 0;
    }
 retry:
    /*
     * Task can not go away as we did a get_task() before !
     */
    raw_spin_lock_irqsave(&task->pi_lock, flags);

    waiter = task->pi_blocked_on;
    /*
     * Check whether the end of the boosting chain has been
     * reached or the state of the chain has changed while we
     * dropped the locks.
     */
    if (!waiter)
        goto out_unlock_pi;

    /*
     * Check the orig_waiter state. After we dropped the locks,
     * the previous owner of the lock might have released the lock.
     */
    if (orig_waiter && !rt_mutex_owner(orig_lock))
        goto out_unlock_pi;

    /*
     * Drop out, when the task has no waiters. Note,
     * top_waiter can be NULL, when we are in the deboosting
     * mode!
     */
    if (top_waiter && (!task_has_pi_waiters(task) ||
               top_waiter != task_top_pi_waiter(task)))
        goto out_unlock_pi;

    /*
     * When deadlock detection is off then we check, if further
     * priority adjustment is necessary.
     */
    if (!detect_deadlock && waiter->list_entry.prio == task->prio)
        goto out_unlock_pi;

    lock = waiter->lock;
    if (!raw_spin_trylock(&lock->wait_lock)) {
        raw_spin_unlock_irqrestore(&task->pi_lock, flags);
        cpu_relax();
        goto retry;
    }

    /* Deadlock detection */
    if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
        debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
        raw_spin_unlock(&lock->wait_lock);
        ret = deadlock_detect ? -EDEADLK : 0;
        goto out_unlock_pi;
    }

    top_waiter = rt_mutex_top_waiter(lock);

    /* Requeue the waiter */
    plist_del(&waiter->list_entry, &lock->wait_list);
    waiter->list_entry.prio = task->prio;
    plist_add(&waiter->list_entry, &lock->wait_list);

    /* Release the task */
    raw_spin_unlock_irqrestore(&task->pi_lock, flags);
    if (!rt_mutex_owner(lock)) {
        /*
         * If the requeue above changed the top waiter, then we need
         * to wake the new top waiter up to try to get the lock.
         */

        if (top_waiter != rt_mutex_top_waiter(lock))
            wake_up_process(rt_mutex_top_waiter(lock)->task);
        raw_spin_unlock(&lock->wait_lock);
        goto out_put_task;
    }
    put_task_struct(task);

    /* Grab the next task */
    task = rt_mutex_owner(lock);
    get_task_struct(task);
    raw_spin_lock_irqsave(&task->pi_lock, flags);

    if (waiter == rt_mutex_top_waiter(lock)) {
        /* Boost the owner */
        plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
        waiter->pi_list_entry.prio = waiter->list_entry.prio;
        plist_add(&waiter->pi_list_entry, &task->pi_waiters);
        __rt_mutex_adjust_prio(task);

    } else if (top_waiter == waiter) {
        /* Deboost the owner */
        plist_del(&waiter->pi_list_entry, &task->pi_waiters);
        waiter = rt_mutex_top_waiter(lock);
        waiter->pi_list_entry.prio = waiter->list_entry.prio;
        plist_add(&waiter->pi_list_entry, &task->pi_waiters);
        __rt_mutex_adjust_prio(task);
    }

    raw_spin_unlock_irqrestore(&task->pi_lock, flags);

    top_waiter = rt_mutex_top_waiter(lock);
    raw_spin_unlock(&lock->wait_lock);

    if (!detect_deadlock && waiter != top_waiter)
        goto out_put_task;

    goto again;

 out_unlock_pi:
    raw_spin_unlock_irqrestore(&task->pi_lock, flags);
 out_put_task:
    put_task_struct(task);

    return ret;
}

/*
 * Try to take an rt-mutex
 *
 * Must be called with lock->wait_lock held.
 *
 * @lock:   the lock to be acquired.
 * @task:   the task which wants to acquire the lock
 * @waiter: the waiter that is queued to the lock's wait list. (could be NULL)
 */
static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
        struct rt_mutex_waiter *waiter)
{
    /*
     * We have to be careful here if the atomic speedups are
     * enabled, such that, when
     *  - no other waiter is on the lock
     *  - the lock has been released since we did the cmpxchg
     * the lock can be released or taken while we are doing the
     * checks and marking the lock with RT_MUTEX_HAS_WAITERS.
     *
     * The atomic acquire/release aware variant of
     * mark_rt_mutex_waiters uses a cmpxchg loop. After setting
     * the WAITERS bit, the atomic release / acquire can not
     * happen anymore and lock->wait_lock protects us from the
     * non-atomic case.
     *
     * Note, that this might set lock->owner =
     * RT_MUTEX_HAS_WAITERS in the case the lock is not contended
     * any more. This is fixed up when we take the ownership.
     * This is the transitional state explained at the top of this file.
     */
    mark_rt_mutex_waiters(lock);

    if (rt_mutex_owner(lock))
        return 0;

    /*
     * It will get the lock because of one of these conditions:
     * 1) there is no waiter
     * 2) higher priority than waiters
     * 3) it is top waiter
     */
    if (rt_mutex_has_waiters(lock)) {
        if (task->prio >= rt_mutex_top_waiter(lock)->list_entry.prio) {
            if (!waiter || waiter != rt_mutex_top_waiter(lock))
                return 0;
        }
    }

    if (waiter || rt_mutex_has_waiters(lock)) {
        unsigned long flags;
        struct rt_mutex_waiter *top;

        raw_spin_lock_irqsave(&task->pi_lock, flags);

        /* remove the queued waiter. */
        if (waiter) {
            plist_del(&waiter->list_entry, &lock->wait_list);
            task->pi_blocked_on = NULL;
        }

        /*
         * We have to enqueue the top waiter(if it exists) into
         * task->pi_waiters list.
         */
        if (rt_mutex_has_waiters(lock)) {
            top = rt_mutex_top_waiter(lock);
            top->pi_list_entry.prio = top->list_entry.prio;
            plist_add(&top->pi_list_entry, &task->pi_waiters);
        }
        raw_spin_unlock_irqrestore(&task->pi_lock, flags);
    }

    /* We got the lock. */
    debug_rt_mutex_lock(lock);

    rt_mutex_set_owner(lock, task);

    rt_mutex_deadlock_account_lock(lock, task);

    return 1;
}

/*
 * Task blocks on lock.
 *
 * Prepare waiter and propagate pi chain
 *
 * This must be called with lock->wait_lock held.
 */
static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
                   struct rt_mutex_waiter *waiter,
                   struct task_struct *task,
                   int detect_deadlock)
{
    struct task_struct *owner = rt_mutex_owner(lock);
    struct rt_mutex_waiter *top_waiter = waiter;
    unsigned long flags;
    int chain_walk = 0, res;

    raw_spin_lock_irqsave(&task->pi_lock, flags);
    __rt_mutex_adjust_prio(task);
    waiter->task = task;
    waiter->lock = lock;
    plist_node_init(&waiter->list_entry, task->prio);
    plist_node_init(&waiter->pi_list_entry, task->prio);

    /* Get the top priority waiter on the lock */
    if (rt_mutex_has_waiters(lock))
        top_waiter = rt_mutex_top_waiter(lock);
    plist_add(&waiter->list_entry, &lock->wait_list);

    task->pi_blocked_on = waiter;

    raw_spin_unlock_irqrestore(&task->pi_lock, flags);

    if (!owner)
        return 0;

    if (waiter == rt_mutex_top_waiter(lock)) {
        raw_spin_lock_irqsave(&owner->pi_lock, flags);
        plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
        plist_add(&waiter->pi_list_entry, &owner->pi_waiters);

        __rt_mutex_adjust_prio(owner);
        if (owner->pi_blocked_on)
            chain_walk = 1;
        raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
    }
    else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock))
        chain_walk = 1;

    if (!chain_walk)
        return 0;

    /*
     * The owner can't disappear while holding a lock,
     * so the owner struct is protected by wait_lock.
     * Gets dropped in rt_mutex_adjust_prio_chain()!
     */
    get_task_struct(owner);

    raw_spin_unlock(&lock->wait_lock);

    res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
                     task);

    raw_spin_lock(&lock->wait_lock);

    return res;
}

/*
 * Wake up the next waiter on the lock.
 *
 * Remove the top waiter from the current tasks waiter list and wake it up.
 *
 * Called with lock->wait_lock held.
 */
static void wakeup_next_waiter(struct rt_mutex *lock)
{
    struct rt_mutex_waiter *waiter;
    unsigned long flags;

    raw_spin_lock_irqsave(&current->pi_lock, flags);

    waiter = rt_mutex_top_waiter(lock);

    /*
     * Remove it from current->pi_waiters. We do not adjust a
     * possible priority boost right now. We execute wakeup in the
     * boosted mode and go back to normal after releasing
     * lock->wait_lock.
     */
    plist_del(&waiter->pi_list_entry, &current->pi_waiters);

    rt_mutex_set_owner(lock, NULL);

    raw_spin_unlock_irqrestore(&current->pi_lock, flags);

    wake_up_process(waiter->task);
}

/*
 * Remove a waiter from a lock and give up
 *
 * Must be called with lock->wait_lock held and
 * have just failed to try_to_take_rt_mutex().
 */
static void remove_waiter(struct rt_mutex *lock,
              struct rt_mutex_waiter *waiter)
{
    int first = (waiter == rt_mutex_top_waiter(lock));
    struct task_struct *owner = rt_mutex_owner(lock);
    unsigned long flags;
    int chain_walk = 0;

    raw_spin_lock_irqsave(&current->pi_lock, flags);
    plist_del(&waiter->list_entry, &lock->wait_list);
    current->pi_blocked_on = NULL;
    raw_spin_unlock_irqrestore(&current->pi_lock, flags);

    if (!owner)
        return;

    if (first) {

        raw_spin_lock_irqsave(&owner->pi_lock, flags);

        plist_del(&waiter->pi_list_entry, &owner->pi_waiters);

        if (rt_mutex_has_waiters(lock)) {
            struct rt_mutex_waiter *next;

            next = rt_mutex_top_waiter(lock);
            plist_add(&next->pi_list_entry, &owner->pi_waiters);
        }
        __rt_mutex_adjust_prio(owner);

        if (owner->pi_blocked_on)
            chain_walk = 1;

        raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
    }

    WARN_ON(!plist_node_empty(&waiter->pi_list_entry));

    if (!chain_walk)
        return;

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

    raw_spin_unlock(&lock->wait_lock);

    rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);

    raw_spin_lock(&lock->wait_lock);
}

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

    raw_spin_lock_irqsave(&task->pi_lock, flags);

    waiter = task->pi_blocked_on;
    if (!waiter || waiter->list_entry.prio == task->prio) {
        raw_spin_unlock_irqrestore(&task->pi_lock, flags);
        return;
    }

    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, 0, NULL, NULL, task);
}

static int __sched
__rt_mutex_slowlock(struct rt_mutex *lock, int state,
            struct hrtimer_sleeper *timeout,
            struct rt_mutex_waiter *waiter)
{
    int ret = 0;

    for (;;) {
        /* Try to acquire the lock: */
        if (try_to_take_rt_mutex(lock, current, waiter))
            break;

        /*
         * TASK_INTERRUPTIBLE checks for signals and
         * timeout. Ignored otherwise.
         */
        if (unlikely(state == TASK_INTERRUPTIBLE)) {
            /* Signal pending? */
            if (signal_pending(current))
                ret = -EINTR;
            if (timeout && !timeout->task)
                ret = -ETIMEDOUT;
            if (ret)
                break;
        }

        raw_spin_unlock(&lock->wait_lock);

        debug_rt_mutex_print_deadlock(waiter);

        schedule_rt_mutex(lock);

        raw_spin_lock(&lock->wait_lock);
        set_current_state(state);
    }

    return ret;
}

/*
 * Slow path lock function:
 */
static int __sched
rt_mutex_slowlock(struct rt_mutex *lock, int state,
          struct hrtimer_sleeper *timeout,
          int detect_deadlock)
{
    struct rt_mutex_waiter waiter;
    int ret = 0;

    debug_rt_mutex_init_waiter(&waiter);

    raw_spin_lock(&lock->wait_lock);

    /* Try to acquire the lock again: */
    if (try_to_take_rt_mutex(lock, current, NULL)) {
        raw_spin_unlock(&lock->wait_lock);
        return 0;
    }

    set_current_state(state);

    /* Setup the timer, when timeout != NULL */
    if (unlikely(timeout)) {
        hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
        if (!hrtimer_active(&timeout->timer))
            timeout->task = NULL;
    }

    ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock);

    if (likely(!ret))
        ret = __rt_mutex_slowlock(lock, state, timeout, &waiter);

    set_current_state(TASK_RUNNING);

    if (unlikely(ret))
        remove_waiter(lock, &waiter);

    /*
     * try_to_take_rt_mutex() sets the waiter bit
     * unconditionally. We might have to fix that up.
     */
    fixup_rt_mutex_waiters(lock);

    raw_spin_unlock(&lock->wait_lock);

    /* Remove pending timer: */
    if (unlikely(timeout))
        hrtimer_cancel(&timeout->timer);

    debug_rt_mutex_free_waiter(&waiter);

    return ret;
}

/*
 * Slow path try-lock function:
 */
static inline int
rt_mutex_slowtrylock(struct rt_mutex *lock)
{
    int ret = 0;

    raw_spin_lock(&lock->wait_lock);

    if (likely(rt_mutex_owner(lock) != current)) {

        ret = try_to_take_rt_mutex(lock, current, NULL);
        /*
         * try_to_take_rt_mutex() sets the lock waiters
         * bit unconditionally. Clean this up.
         */
        fixup_rt_mutex_waiters(lock);
    }

    raw_spin_unlock(&lock->wait_lock);

    return ret;
}

/*
 * Slow path to release a rt-mutex:
 */
static void __sched
rt_mutex_slowunlock(struct rt_mutex *lock)
{
    raw_spin_lock(&lock->wait_lock);

    debug_rt_mutex_unlock(lock);

    rt_mutex_deadlock_account_unlock(current);

    if (!rt_mutex_has_waiters(lock)) {
        lock->owner = NULL;
        raw_spin_unlock(&lock->wait_lock);
        return;
    }

    wakeup_next_waiter(lock);

    raw_spin_unlock(&lock->wait_lock);

    /* Undo pi boosting if necessary: */
    rt_mutex_adjust_prio(current);
}

/*
 * 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 inline int
rt_mutex_fastlock(struct rt_mutex *lock, int state,
          int detect_deadlock,
          int (*slowfn)(struct rt_mutex *lock, int state,
                struct hrtimer_sleeper *timeout,
                int detect_deadlock))
{
    if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
        rt_mutex_deadlock_account_lock(lock, current);
        return 0;
    } else
        return slowfn(lock, state, NULL, detect_deadlock);
}

static inline int
rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
            struct hrtimer_sleeper *timeout, int detect_deadlock,
            int (*slowfn)(struct rt_mutex *lock, int state,
                      struct hrtimer_sleeper *timeout,
                      int detect_deadlock))
{
    if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
        rt_mutex_deadlock_account_lock(lock, current);
        return 0;
    } else
        return slowfn(lock, state, timeout, detect_deadlock);
}

static inline int
rt_mutex_fasttrylock(struct rt_mutex *lock,
             int (*slowfn)(struct rt_mutex *lock))
{
    if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
        rt_mutex_deadlock_account_lock(lock, current);
        return 1;
    }
    return slowfn(lock);
}

static inline void
rt_mutex_fastunlock(struct rt_mutex *lock,
            void (*slowfn)(struct rt_mutex *lock))
{
    if (likely(rt_mutex_cmpxchg(lock, current, NULL)))
        rt_mutex_deadlock_account_unlock(current);
    else
        slowfn(lock);
}

void __sched rt_mutex_lock(struct rt_mutex *lock)
{
    might_sleep();

    rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock);
}
EXPORT_SYMBOL_GPL(rt_mutex_lock);

int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock,
                         int detect_deadlock)
{
    might_sleep();

    return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE,
                 detect_deadlock, rt_mutex_slowlock);
}
EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);

int
rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout,
            int detect_deadlock)
{
    might_sleep();

    return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
                       detect_deadlock, rt_mutex_slowlock);
}
EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);

int __sched rt_mutex_trylock(struct rt_mutex *lock)
{
    return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
}
EXPORT_SYMBOL_GPL(rt_mutex_trylock);

void __sched rt_mutex_unlock(struct rt_mutex *lock)
{
    rt_mutex_fastunlock(lock, rt_mutex_slowunlock);
}
EXPORT_SYMBOL_GPL(rt_mutex_unlock);

void rt_mutex_destroy(struct rt_mutex *lock)
{
    WARN_ON(rt_mutex_is_locked(lock));
#ifdef CONFIG_DEBUG_RT_MUTEXES
    lock->magic = NULL;
#endif
}

EXPORT_SYMBOL_GPL(rt_mutex_destroy);

void __rt_mutex_init(struct rt_mutex *lock, const char *name)
{
    lock->owner = NULL;
    raw_spin_lock_init(&lock->wait_lock);
    plist_head_init(&lock->wait_list);

    debug_rt_mutex_init(lock, name);
}
EXPORT_SYMBOL_GPL(__rt_mutex_init);

void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
                struct task_struct *proxy_owner)
{
    __rt_mutex_init(lock, NULL);
    debug_rt_mutex_proxy_lock(lock, proxy_owner);
    rt_mutex_set_owner(lock, proxy_owner);
    rt_mutex_deadlock_account_lock(lock, proxy_owner);
}

void rt_mutex_proxy_unlock(struct rt_mutex *lock,
               struct task_struct *proxy_owner)
{
    debug_rt_mutex_proxy_unlock(lock);
    rt_mutex_set_owner(lock, NULL);
    rt_mutex_deadlock_account_unlock(proxy_owner);
}

int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
                  struct rt_mutex_waiter *waiter,
                  struct task_struct *task, int detect_deadlock)
{
    int ret;

    raw_spin_lock(&lock->wait_lock);

    if (try_to_take_rt_mutex(lock, task, NULL)) {
        raw_spin_unlock(&lock->wait_lock);
        return 1;
    }

    ret = task_blocks_on_rt_mutex(lock, waiter, task, detect_deadlock);

    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;
    }

    if (unlikely(ret))
        remove_waiter(lock, waiter);

    raw_spin_unlock(&lock->wait_lock);

    debug_rt_mutex_print_deadlock(waiter);

    return ret;
}

struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock)
{
    if (!rt_mutex_has_waiters(lock))
        return NULL;

    return rt_mutex_top_waiter(lock)->task;
}

int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
                   struct hrtimer_sleeper *to,
                   struct rt_mutex_waiter *waiter,
                   int detect_deadlock)
{
    int ret;

    raw_spin_lock(&lock->wait_lock);

    set_current_state(TASK_INTERRUPTIBLE);

    ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter);

    set_current_state(TASK_RUNNING);

    if (unlikely(ret))
        remove_waiter(lock, waiter);

    /*
     * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
     * have to fix that up.
     */
    fixup_rt_mutex_waiters(lock);

    raw_spin_unlock(&lock->wait_lock);

    return ret;
}