/*
 * Remove a waiter from a lock
 *
 * Must be called with lock->wait_lock held
 */
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 boost = 0;

    spin_lock_irqsave(&current->pi_lock, flags);
    plist_del(&waiter->list_entry, &lock->wait_list);
    waiter->task = NULL;
    current->pi_blocked_on = NULL;
    spin_unlock_irqrestore(&current->pi_lock, flags);

    if (first && owner != current) {

        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) {
            boost = 1;
            /* gets dropped in rt_mutex_adjust_prio_chain()! */
            get_task_struct(owner);
        }
        spin_unlock_irqrestore(&owner->pi_lock, flags);
    }

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

    if (!boost)
        return;

    spin_unlock(&lock->wait_lock);

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

    spin_lock(&lock->wait_lock);
}

/**
 * pm_qos_update_target - manages the constraints list and calls the notifiers
 *  if needed
 * @c: constraints data struct
 * @node: request to add to the list, to update or to remove
 * @action: action to take on the constraints list
 * @value: value of the request to add or update
 *
 * This function returns 1 if the aggregated constraint value has changed, 0
 *  otherwise.
 */
int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node,
			 enum pm_qos_req_action action, int value)
{
	unsigned long flags;
	int prev_value, curr_value, new_value;

	spin_lock_irqsave(&pm_qos_lock, flags);
	prev_value = pm_qos_get_value(c);
	if (value == PM_QOS_DEFAULT_VALUE)
		new_value = c->default_value;
	else
		new_value = value;

	switch (action) {
	case PM_QOS_REMOVE_REQ:
		plist_del(node, &c->list);
		break;
	case PM_QOS_UPDATE_REQ:
		/*
		 * to change the list, we atomically remove, reinit
		 * with new value and add, then see if the extremal
		 * changed
		 */
		plist_del(node, &c->list);
	case PM_QOS_ADD_REQ:
		plist_node_init(node, new_value);
		plist_add(node, &c->list);
		break;
	default:
		/* no action */
		;
	}

	curr_value = pm_qos_get_value(c);
	pm_qos_set_value(c, curr_value);

	spin_unlock_irqrestore(&pm_qos_lock, flags);

	if (prev_value != curr_value) {
		blocking_notifier_call_chain(c->notifiers,
					     (unsigned long)curr_value,
					     NULL);
		return 1;
	} else {
		return 0;
	}
}

/*
 * 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,
                                   int detect_deadlock)
{
    struct task_struct *owner = rt_mutex_owner(lock);
    struct rt_mutex_waiter *top_waiter = waiter;
    unsigned long flags;
    int boost = 0, res;

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

    current->pi_blocked_on = waiter;

    spin_unlock_irqrestore(&current->pi_lock, flags);

    if (waiter == rt_mutex_top_waiter(lock)) {
        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) {
            boost = 1;
            /* gets dropped in rt_mutex_adjust_prio_chain()! */
            get_task_struct(owner);
        }
        spin_unlock_irqrestore(&owner->pi_lock, flags);
    }
    else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) {
        spin_lock_irqsave(&owner->pi_lock, flags);
        if (owner->pi_blocked_on) {
            boost = 1;
            /* gets dropped in rt_mutex_adjust_prio_chain()! */
            get_task_struct(owner);
        }
        spin_unlock_irqrestore(&owner->pi_lock, flags);
    }
    if (!boost)
        return 0;

    spin_unlock(&lock->wait_lock);

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

    spin_lock(&lock->wait_lock);

    return res;
}

/*
 * 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 (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;
}

/*
 * Optimization: check if we can steal the lock from the
 * assigned pending owner [which might not have taken the
 * lock yet]:
 */
static inline int try_to_steal_lock(struct rt_mutex *lock,
				    struct task_struct *task)
{
	struct task_struct *pendowner = rt_mutex_owner(lock);
	struct rt_mutex_waiter *next;
	unsigned long flags;

	if (!rt_mutex_owner_pending(lock))
		return 0;

	if (pendowner == task)
		return 1;

	raw_spin_lock_irqsave(&pendowner->pi_lock, flags);
	if (task->prio >= pendowner->prio) {
		raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags);
		return 0;
	}

	/*
	 * Check if a waiter is enqueued on the pending owners
	 * pi_waiters list. Remove it and readjust pending owners
	 * priority.
	 */
	if (likely(!rt_mutex_has_waiters(lock))) {
		raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags);
		return 1;
	}

	/* No chain handling, pending owner is not blocked on anything: */
	next = rt_mutex_top_waiter(lock);
	plist_del(&next->pi_list_entry, &pendowner->pi_waiters);
	__rt_mutex_adjust_prio(pendowner);
	raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags);

	/*
	 * We are going to steal the lock and a waiter was
	 * enqueued on the pending owners pi_waiters queue. So
	 * we have to enqueue this waiter into
	 * task->pi_waiters list. This covers the case,
	 * where task is boosted because it holds another
	 * lock and gets unboosted because the booster is
	 * interrupted, so we would delay a waiter with higher
	 * priority as task->normal_prio.
	 *
	 * Note: in the rare case of a SCHED_OTHER task changing
	 * its priority and thus stealing the lock, next->task
	 * might be task:
	 */
	if (likely(next->task != task)) {
		raw_spin_lock_irqsave(&task->pi_lock, flags);
		plist_add(&next->pi_list_entry, &task->pi_waiters);
		__rt_mutex_adjust_prio(task);
		raw_spin_unlock_irqrestore(&task->pi_lock, flags);
	}
	return 1;
}

static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
{
	plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);

	/* Update the new highest prio pushable task */
	if (has_pushable_tasks(rq)) {
		p = plist_first_entry(&rq->rt.pushable_tasks,
				      struct task_struct, pushable_tasks);
		rq->rt.highest_prio.next = p->prio;
	} else

static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
{
	plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
	plist_node_init(&p->pushable_tasks, p->prio);
	plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);

	/* Update the highest prio pushable task */
	if (p->prio < rq->rt.highest_prio.next)
		rq->rt.highest_prio.next = p->prio;
}

/*
 * 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);
}

/*
 * 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;
}

/*
 * 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);
//.........这里部分代码省略.........

/*
 * 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;

	/*
	 * Early deadlock detection. We really don't want the task to
	 * enqueue on itself just to untangle the mess later. It's not
	 * only an optimization. We drop the locks, so another waiter
	 * can come in before the chain walk detects the deadlock. So
	 * the other will detect the deadlock and return -EDEADLOCK,
	 * which is wrong, as the other waiter is not in a deadlock
	 * situation.
	 */
	if (detect_deadlock && owner == task)
		return -EDEADLK;

	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;
}