/*
   * padata.c - generic interface to process data streams in parallel
   *

   * See Documentation/padata.txt for an api documentation.
   *

   * Copyright (C) 2008, 2009 secunet Security Networks AG
   * Copyright (C) 2008, 2009 Steffen Klassert <steffen.klassert@secunet.com>
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms and conditions of the GNU General Public License,
   * version 2, as published by the Free Software Foundation.
   *
   * This program is distributed in the hope it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
   * more details.
   *
   * You should have received a copy of the GNU General Public License along with
   * this program; if not, write to the Free Software Foundation, Inc.,
   * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
   */

  #include <linux/export.h>

  #include <linux/cpumask.h>
  #include <linux/err.h>
  #include <linux/cpu.h>
  #include <linux/padata.h>
  #include <linux/mutex.h>
  #include <linux/sched.h>

  #include <linux/slab.h>

  #include <linux/sysfs.h>

  #include <linux/rcupdate.h>

  #include <linux/module.h>

  #define MAX_OBJ_NUM 1000

  
  static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index)
  {
  	int cpu, target_cpu;

  	target_cpu = cpumask_first(pd->cpumask.pcpu);

  	for (cpu = 0; cpu < cpu_index; cpu++)

  		target_cpu = cpumask_next(target_cpu, pd->cpumask.pcpu);

  
  	return target_cpu;
  }

  static int padata_cpu_hash(struct parallel_data *pd)

  {

  	unsigned int seq_nr;

  	int cpu_index;

  
  	/*
  	 * Hash the sequence numbers to the cpus by taking
  	 * seq_nr mod. number of cpus in use.
  	 */

  	seq_nr = atomic_inc_return(&pd->seq_nr);
  	cpu_index = seq_nr % cpumask_weight(pd->cpumask.pcpu);

  
  	return padata_index_to_cpu(pd, cpu_index);
  }

  static void padata_parallel_worker(struct work_struct *parallel_work)

  {

  	struct padata_parallel_queue *pqueue;

  	LIST_HEAD(local_list);
  
  	local_bh_disable();

  	pqueue = container_of(parallel_work,
  			      struct padata_parallel_queue, work);

  	spin_lock(&pqueue->parallel.lock);
  	list_replace_init(&pqueue->parallel.list, &local_list);
  	spin_unlock(&pqueue->parallel.lock);

  
  	while (!list_empty(&local_list)) {
  		struct padata_priv *padata;
  
  		padata = list_entry(local_list.next,
  				    struct padata_priv, list);
  
  		list_del_init(&padata->list);
  
  		padata->parallel(padata);
  	}
  
  	local_bh_enable();
  }

  /**

   * padata_do_parallel - padata parallelization function
   *
   * @pinst: padata instance
   * @padata: object to be parallelized
   * @cb_cpu: cpu the serialization callback function will run on,

   *          must be in the serial cpumask of padata(i.e. cpumask.cbcpu).

   *
   * The parallelization callback function will run with BHs off.
   * Note: Every object which is parallelized by padata_do_parallel
   * must be seen by padata_do_serial.
   */
  int padata_do_parallel(struct padata_instance *pinst,
  		       struct padata_priv *padata, int cb_cpu)
  {
  	int target_cpu, err;

  	struct padata_parallel_queue *queue;

  	struct parallel_data *pd;
  
  	rcu_read_lock_bh();

  	pd = rcu_dereference_bh(pinst->pd);

  	err = -EINVAL;

  	if (!(pinst->flags & PADATA_INIT) || pinst->flags & PADATA_INVALID)

  		goto out;

  	if (!cpumask_test_cpu(cb_cpu, pd->cpumask.cbcpu))

  		goto out;
  
  	err =  -EBUSY;
  	if ((pinst->flags & PADATA_RESET))
  		goto out;
  
  	if (atomic_read(&pd->refcnt) >= MAX_OBJ_NUM)
  		goto out;

  	err = 0;

  	atomic_inc(&pd->refcnt);
  	padata->pd = pd;
  	padata->cb_cpu = cb_cpu;

  	target_cpu = padata_cpu_hash(pd);

  	queue = per_cpu_ptr(pd->pqueue, target_cpu);

  
  	spin_lock(&queue->parallel.lock);
  	list_add_tail(&padata->list, &queue->parallel.list);
  	spin_unlock(&queue->parallel.lock);

  	queue_work_on(target_cpu, pinst->wq, &queue->work);

  
  out:
  	rcu_read_unlock_bh();
  
  	return err;
  }
  EXPORT_SYMBOL(padata_do_parallel);

  /*
   * padata_get_next - Get the next object that needs serialization.
   *
   * Return values are:
   *
   * A pointer to the control struct of the next object that needs
   * serialization, if present in one of the percpu reorder queues.
   *

   * -EINPROGRESS, if the next object that needs serialization will
   *  be parallel processed by another cpu and is not yet present in
   *  the cpu's reorder queue.
   *
   * -ENODATA, if this cpu has to do the parallel processing for
   *  the next object.
   */

  static struct padata_priv *padata_get_next(struct parallel_data *pd)
  {

  	int cpu, num_cpus;

  	unsigned int next_nr, next_index;

  	struct padata_parallel_queue *next_queue;

  	struct padata_priv *padata;
  	struct padata_list *reorder;

  	num_cpus = cpumask_weight(pd->cpumask.pcpu);

  	/*
  	 * Calculate the percpu reorder queue and the sequence
  	 * number of the next object.
  	 */
  	next_nr = pd->processed;
  	next_index = next_nr % num_cpus;
  	cpu = padata_index_to_cpu(pd, next_index);

  	next_queue = per_cpu_ptr(pd->pqueue, cpu);

  	reorder = &next_queue->reorder;

  	spin_lock(&reorder->lock);

  	if (!list_empty(&reorder->list)) {
  		padata = list_entry(reorder->list.next,
  				    struct padata_priv, list);

  		list_del_init(&padata->list);
  		atomic_dec(&pd->reorder_objects);

  		pd->processed++;

  		spin_unlock(&reorder->lock);

  		goto out;
  	}

  	spin_unlock(&reorder->lock);

  	if (__this_cpu_read(pd->pqueue->cpu_index) == next_queue->cpu_index) {

  		padata = ERR_PTR(-ENODATA);
  		goto out;
  	}
  
  	padata = ERR_PTR(-EINPROGRESS);
  out:
  	return padata;
  }
  
  static void padata_reorder(struct parallel_data *pd)
  {

  	int cb_cpu;

  	struct padata_priv *padata;

  	struct padata_serial_queue *squeue;

  	struct padata_instance *pinst = pd->pinst;

  	/*
  	 * We need to ensure that only one cpu can work on dequeueing of
  	 * the reorder queue the time. Calculating in which percpu reorder
  	 * queue the next object will arrive takes some time. A spinlock
  	 * would be highly contended. Also it is not clear in which order
  	 * the objects arrive to the reorder queues. So a cpu could wait to
  	 * get the lock just to notice that there is nothing to do at the
  	 * moment. Therefore we use a trylock and let the holder of the lock
  	 * care for all the objects enqueued during the holdtime of the lock.
  	 */

  	if (!spin_trylock_bh(&pd->lock))

  		return;

  
  	while (1) {
  		padata = padata_get_next(pd);

  		/*

  		 * If the next object that needs serialization is parallel
  		 * processed by another cpu and is still on it's way to the
  		 * cpu's reorder queue, nothing to do for now.

  		 */

  		if (PTR_ERR(padata) == -EINPROGRESS)

  			break;

  		/*
  		 * This cpu has to do the parallel processing of the next
  		 * object. It's waiting in the cpu's parallelization queue,

  		 * so exit immediately.

  		 */

  		if (PTR_ERR(padata) == -ENODATA) {

  			del_timer(&pd->timer);

  			spin_unlock_bh(&pd->lock);

  			return;

  		}

  		cb_cpu = padata->cb_cpu;
  		squeue = per_cpu_ptr(pd->squeue, cb_cpu);

  		spin_lock(&squeue->serial.lock);
  		list_add_tail(&padata->list, &squeue->serial.list);
  		spin_unlock(&squeue->serial.lock);

  		queue_work_on(cb_cpu, pinst->wq, &squeue->work);

  	}
  
  	spin_unlock_bh(&pd->lock);

  	/*
  	 * The next object that needs serialization might have arrived to
  	 * the reorder queues in the meantime, we will be called again

  	 * from the timer function if no one else cares for it.

  	 */

  	if (atomic_read(&pd->reorder_objects)
  			&& !(pinst->flags & PADATA_RESET))
  		mod_timer(&pd->timer, jiffies + HZ);
  	else
  		del_timer(&pd->timer);

  	return;
  }

  static void padata_reorder_timer(unsigned long arg)
  {
  	struct parallel_data *pd = (struct parallel_data *)arg;
  
  	padata_reorder(pd);
  }

  static void padata_serial_worker(struct work_struct *serial_work)

  {

  	struct padata_serial_queue *squeue;

  	struct parallel_data *pd;
  	LIST_HEAD(local_list);
  
  	local_bh_disable();

  	squeue = container_of(serial_work, struct padata_serial_queue, work);
  	pd = squeue->pd;

  	spin_lock(&squeue->serial.lock);
  	list_replace_init(&squeue->serial.list, &local_list);
  	spin_unlock(&squeue->serial.lock);

  
  	while (!list_empty(&local_list)) {
  		struct padata_priv *padata;
  
  		padata = list_entry(local_list.next,
  				    struct padata_priv, list);
  
  		list_del_init(&padata->list);
  
  		padata->serial(padata);
  		atomic_dec(&pd->refcnt);
  	}
  	local_bh_enable();
  }

  /**

   * padata_do_serial - padata serialization function
   *
   * @padata: object to be serialized.
   *
   * padata_do_serial must be called for every parallelized object.
   * The serialization callback function will run with BHs off.
   */
  void padata_do_serial(struct padata_priv *padata)
  {
  	int cpu;

  	struct padata_parallel_queue *pqueue;

  	struct parallel_data *pd;
  
  	pd = padata->pd;
  
  	cpu = get_cpu();

  	pqueue = per_cpu_ptr(pd->pqueue, cpu);

  	spin_lock(&pqueue->reorder.lock);

  	atomic_inc(&pd->reorder_objects);

  	list_add_tail(&padata->list, &pqueue->reorder.list);
  	spin_unlock(&pqueue->reorder.lock);

  
  	put_cpu();
  
  	padata_reorder(pd);
  }
  EXPORT_SYMBOL(padata_do_serial);

  static int padata_setup_cpumasks(struct parallel_data *pd,
  				 const struct cpumask *pcpumask,
  				 const struct cpumask *cbcpumask)

  {

  	if (!alloc_cpumask_var(&pd->cpumask.pcpu, GFP_KERNEL))
  		return -ENOMEM;

  	cpumask_and(pd->cpumask.pcpu, pcpumask, cpu_online_mask);

  	if (!alloc_cpumask_var(&pd->cpumask.cbcpu, GFP_KERNEL)) {

  		free_cpumask_var(pd->cpumask.pcpu);

  		return -ENOMEM;
  	}

  	cpumask_and(pd->cpumask.cbcpu, cbcpumask, cpu_online_mask);

  	return 0;
  }

  static void __padata_list_init(struct padata_list *pd_list)
  {
  	INIT_LIST_HEAD(&pd_list->list);
  	spin_lock_init(&pd_list->lock);
  }

  /* Initialize all percpu queues used by serial workers */
  static void padata_init_squeues(struct parallel_data *pd)
  {
  	int cpu;
  	struct padata_serial_queue *squeue;

  	for_each_cpu(cpu, pd->cpumask.cbcpu) {
  		squeue = per_cpu_ptr(pd->squeue, cpu);
  		squeue->pd = pd;
  		__padata_list_init(&squeue->serial);
  		INIT_WORK(&squeue->work, padata_serial_worker);
  	}
  }

  /* Initialize all percpu queues used by parallel workers */
  static void padata_init_pqueues(struct parallel_data *pd)
  {

  	int cpu_index, cpu;

  	struct padata_parallel_queue *pqueue;

  	cpu_index = 0;
  	for_each_cpu(cpu, pd->cpumask.pcpu) {
  		pqueue = per_cpu_ptr(pd->pqueue, cpu);
  		pqueue->pd = pd;
  		pqueue->cpu_index = cpu_index;

  		cpu_index++;

  		__padata_list_init(&pqueue->reorder);
  		__padata_list_init(&pqueue->parallel);
  		INIT_WORK(&pqueue->work, padata_parallel_worker);
  		atomic_set(&pqueue->num_obj, 0);

  	}

  }

  /* Allocate and initialize the internal cpumask dependend resources. */
  static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst,
  					     const struct cpumask *pcpumask,
  					     const struct cpumask *cbcpumask)
  {
  	struct parallel_data *pd;

  	pd = kzalloc(sizeof(struct parallel_data), GFP_KERNEL);
  	if (!pd)
  		goto err;

  	pd->pqueue = alloc_percpu(struct padata_parallel_queue);
  	if (!pd->pqueue)
  		goto err_free_pd;
  
  	pd->squeue = alloc_percpu(struct padata_serial_queue);
  	if (!pd->squeue)
  		goto err_free_pqueue;
  	if (padata_setup_cpumasks(pd, pcpumask, cbcpumask) < 0)
  		goto err_free_squeue;

  	padata_init_pqueues(pd);
  	padata_init_squeues(pd);

  	setup_timer(&pd->timer, padata_reorder_timer, (unsigned long)pd);

  	atomic_set(&pd->seq_nr, -1);

  	atomic_set(&pd->reorder_objects, 0);
  	atomic_set(&pd->refcnt, 0);
  	pd->pinst = pinst;
  	spin_lock_init(&pd->lock);
  
  	return pd;

  err_free_squeue:
  	free_percpu(pd->squeue);
  err_free_pqueue:
  	free_percpu(pd->pqueue);

  err_free_pd:
  	kfree(pd);
  err:
  	return NULL;
  }
  
  static void padata_free_pd(struct parallel_data *pd)
  {

  	free_cpumask_var(pd->cpumask.pcpu);
  	free_cpumask_var(pd->cpumask.cbcpu);
  	free_percpu(pd->pqueue);
  	free_percpu(pd->squeue);

  	kfree(pd);
  }

  /* Flush all objects out of the padata queues. */

  static void padata_flush_queues(struct parallel_data *pd)
  {
  	int cpu;

  	struct padata_parallel_queue *pqueue;
  	struct padata_serial_queue *squeue;

  	for_each_cpu(cpu, pd->cpumask.pcpu) {
  		pqueue = per_cpu_ptr(pd->pqueue, cpu);
  		flush_work(&pqueue->work);

  	}
  
  	del_timer_sync(&pd->timer);
  
  	if (atomic_read(&pd->reorder_objects))
  		padata_reorder(pd);

  	for_each_cpu(cpu, pd->cpumask.cbcpu) {
  		squeue = per_cpu_ptr(pd->squeue, cpu);
  		flush_work(&squeue->work);

  	}
  
  	BUG_ON(atomic_read(&pd->refcnt) != 0);
  }

  static void __padata_start(struct padata_instance *pinst)
  {
  	pinst->flags |= PADATA_INIT;
  }

  static void __padata_stop(struct padata_instance *pinst)
  {
  	if (!(pinst->flags & PADATA_INIT))
  		return;
  
  	pinst->flags &= ~PADATA_INIT;
  
  	synchronize_rcu();
  
  	get_online_cpus();
  	padata_flush_queues(pinst->pd);
  	put_online_cpus();
  }

  /* Replace the internal control structure with a new one. */

  static void padata_replace(struct padata_instance *pinst,
  			   struct parallel_data *pd_new)
  {
  	struct parallel_data *pd_old = pinst->pd;

  	int notification_mask = 0;

  
  	pinst->flags |= PADATA_RESET;
  
  	rcu_assign_pointer(pinst->pd, pd_new);
  
  	synchronize_rcu();

  	if (!cpumask_equal(pd_old->cpumask.pcpu, pd_new->cpumask.pcpu))
  		notification_mask |= PADATA_CPU_PARALLEL;
  	if (!cpumask_equal(pd_old->cpumask.cbcpu, pd_new->cpumask.cbcpu))
  		notification_mask |= PADATA_CPU_SERIAL;

  	padata_flush_queues(pd_old);

  	padata_free_pd(pd_old);

  	if (notification_mask)
  		blocking_notifier_call_chain(&pinst->cpumask_change_notifier,

  					     notification_mask,
  					     &pd_new->cpumask);

  
  	pinst->flags &= ~PADATA_RESET;
  }

  /**

   * padata_register_cpumask_notifier - Registers a notifier that will be called
   *                             if either pcpu or cbcpu or both cpumasks change.

   *

   * @pinst: A poineter to padata instance
   * @nblock: A pointer to notifier block.

   */

  int padata_register_cpumask_notifier(struct padata_instance *pinst,
  				     struct notifier_block *nblock)

  {

  	return blocking_notifier_chain_register(&pinst->cpumask_change_notifier,
  						nblock);
  }
  EXPORT_SYMBOL(padata_register_cpumask_notifier);
  
  /**
   * padata_unregister_cpumask_notifier - Unregisters cpumask notifier
   *        registered earlier  using padata_register_cpumask_notifier
   *
   * @pinst: A pointer to data instance.
   * @nlock: A pointer to notifier block.
   */
  int padata_unregister_cpumask_notifier(struct padata_instance *pinst,
  				       struct notifier_block *nblock)
  {
  	return blocking_notifier_chain_unregister(
  		&pinst->cpumask_change_notifier,
  		nblock);
  }
  EXPORT_SYMBOL(padata_unregister_cpumask_notifier);

  /* If cpumask contains no active cpu, we mark the instance as invalid. */
  static bool padata_validate_cpumask(struct padata_instance *pinst,
  				    const struct cpumask *cpumask)
  {

  	if (!cpumask_intersects(cpumask, cpu_online_mask)) {

  		pinst->flags |= PADATA_INVALID;
  		return false;
  	}
  
  	pinst->flags &= ~PADATA_INVALID;
  	return true;
  }

  static int __padata_set_cpumasks(struct padata_instance *pinst,
  				 cpumask_var_t pcpumask,
  				 cpumask_var_t cbcpumask)
  {
  	int valid;

  	struct parallel_data *pd;

  
  	valid = padata_validate_cpumask(pinst, pcpumask);
  	if (!valid) {
  		__padata_stop(pinst);
  		goto out_replace;
  	}
  
  	valid = padata_validate_cpumask(pinst, cbcpumask);
  	if (!valid)
  		__padata_stop(pinst);
  
  out_replace:
  	pd = padata_alloc_pd(pinst, pcpumask, cbcpumask);
  	if (!pd)
  		return -ENOMEM;
  
  	cpumask_copy(pinst->cpumask.pcpu, pcpumask);
  	cpumask_copy(pinst->cpumask.cbcpu, cbcpumask);
  
  	padata_replace(pinst, pd);
  
  	if (valid)
  		__padata_start(pinst);
  
  	return 0;
  }
  
  /**

   * padata_set_cpumask: Sets specified by @cpumask_type cpumask to the value
   *                     equivalent to @cpumask.

   *
   * @pinst: padata instance

   * @cpumask_type: PADATA_CPU_SERIAL or PADATA_CPU_PARALLEL corresponding
   *                to parallel and serial cpumasks respectively.

   * @cpumask: the cpumask to use
   */

  int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type,
  		       cpumask_var_t cpumask)
  {
  	struct cpumask *serial_mask, *parallel_mask;

  	int err = -EINVAL;
  
  	mutex_lock(&pinst->lock);

  	get_online_cpus();

  	switch (cpumask_type) {
  	case PADATA_CPU_PARALLEL:
  		serial_mask = pinst->cpumask.cbcpu;
  		parallel_mask = cpumask;
  		break;
  	case PADATA_CPU_SERIAL:
  		parallel_mask = pinst->cpumask.pcpu;
  		serial_mask = cpumask;
  		break;
  	default:

  		 goto out;

  	}

  	err =  __padata_set_cpumasks(pinst, parallel_mask, serial_mask);

  
  out:

  	put_online_cpus();

  	mutex_unlock(&pinst->lock);
  
  	return err;
  }
  EXPORT_SYMBOL(padata_set_cpumask);

  /**
   * padata_start - start the parallel processing
   *
   * @pinst: padata instance to start
   */
  int padata_start(struct padata_instance *pinst)
  {
  	int err = 0;
  
  	mutex_lock(&pinst->lock);
  
  	if (pinst->flags & PADATA_INVALID)
  		err = -EINVAL;
  
  	 __padata_start(pinst);
  
  	mutex_unlock(&pinst->lock);
  
  	return err;
  }
  EXPORT_SYMBOL(padata_start);
  
  /**
   * padata_stop - stop the parallel processing
   *
   * @pinst: padata instance to stop
   */
  void padata_stop(struct padata_instance *pinst)
  {
  	mutex_lock(&pinst->lock);
  	__padata_stop(pinst);
  	mutex_unlock(&pinst->lock);
  }
  EXPORT_SYMBOL(padata_stop);
  
  #ifdef CONFIG_HOTPLUG_CPU

  static int __padata_add_cpu(struct padata_instance *pinst, int cpu)
  {
  	struct parallel_data *pd;

  	if (cpumask_test_cpu(cpu, cpu_online_mask)) {

  		pd = padata_alloc_pd(pinst, pinst->cpumask.pcpu,
  				     pinst->cpumask.cbcpu);

  		if (!pd)
  			return -ENOMEM;
  
  		padata_replace(pinst, pd);

  		if (padata_validate_cpumask(pinst, pinst->cpumask.pcpu) &&
  		    padata_validate_cpumask(pinst, pinst->cpumask.cbcpu))

  			__padata_start(pinst);

  	}
  
  	return 0;
  }

  static int __padata_remove_cpu(struct padata_instance *pinst, int cpu)
  {

  	struct parallel_data *pd = NULL;

  
  	if (cpumask_test_cpu(cpu, cpu_online_mask)) {

  		if (!padata_validate_cpumask(pinst, pinst->cpumask.pcpu) ||

  		    !padata_validate_cpumask(pinst, pinst->cpumask.cbcpu))

  			__padata_stop(pinst);

  		pd = padata_alloc_pd(pinst, pinst->cpumask.pcpu,
  				     pinst->cpumask.cbcpu);

  		if (!pd)
  			return -ENOMEM;
  
  		padata_replace(pinst, pd);

  
  		cpumask_clear_cpu(cpu, pd->cpumask.cbcpu);
  		cpumask_clear_cpu(cpu, pd->cpumask.pcpu);

  	}
  
  	return 0;
  }

   /**

   * padata_remove_cpu - remove a cpu from the one or both(serial and parallel)

   *                     padata cpumasks.

   *
   * @pinst: padata instance
   * @cpu: cpu to remove

   * @mask: bitmask specifying from which cpumask @cpu should be removed
   *        The @mask may be any combination of the following flags:
   *          PADATA_CPU_SERIAL   - serial cpumask
   *          PADATA_CPU_PARALLEL - parallel cpumask

   */

  int padata_remove_cpu(struct padata_instance *pinst, int cpu, int mask)

  {
  	int err;

  	if (!(mask & (PADATA_CPU_SERIAL | PADATA_CPU_PARALLEL)))
  		return -EINVAL;

  	mutex_lock(&pinst->lock);

  	get_online_cpus();

  	if (mask & PADATA_CPU_SERIAL)
  		cpumask_clear_cpu(cpu, pinst->cpumask.cbcpu);
  	if (mask & PADATA_CPU_PARALLEL)
  		cpumask_clear_cpu(cpu, pinst->cpumask.pcpu);

  	err = __padata_remove_cpu(pinst, cpu);

  	put_online_cpus();

  
  	mutex_unlock(&pinst->lock);
  
  	return err;
  }
  EXPORT_SYMBOL(padata_remove_cpu);

  static inline int pinst_has_cpu(struct padata_instance *pinst, int cpu)
  {
  	return cpumask_test_cpu(cpu, pinst->cpumask.pcpu) ||
  		cpumask_test_cpu(cpu, pinst->cpumask.cbcpu);
  }

  static int padata_cpu_online(unsigned int cpu, struct hlist_node *node)

  {

  	struct padata_instance *pinst;

  	int ret;

  	pinst = hlist_entry_safe(node, struct padata_instance, node);
  	if (!pinst_has_cpu(pinst, cpu))
  		return 0;

  	mutex_lock(&pinst->lock);
  	ret = __padata_add_cpu(pinst, cpu);
  	mutex_unlock(&pinst->lock);
  	return ret;
  }

  static int padata_cpu_prep_down(unsigned int cpu, struct hlist_node *node)
  {
  	struct padata_instance *pinst;
  	int ret;
  
  	pinst = hlist_entry_safe(node, struct padata_instance, node);
  	if (!pinst_has_cpu(pinst, cpu))
  		return 0;

  	mutex_lock(&pinst->lock);
  	ret = __padata_remove_cpu(pinst, cpu);
  	mutex_unlock(&pinst->lock);
  	return ret;

  }

  
  static enum cpuhp_state hp_online;

  #endif

  static void __padata_free(struct padata_instance *pinst)
  {
  #ifdef CONFIG_HOTPLUG_CPU

  	cpuhp_state_remove_instance_nocalls(hp_online, &pinst->node);

  #endif
  
  	padata_stop(pinst);
  	padata_free_pd(pinst->pd);
  	free_cpumask_var(pinst->cpumask.pcpu);
  	free_cpumask_var(pinst->cpumask.cbcpu);
  	kfree(pinst);
  }
  
  #define kobj2pinst(_kobj)					\
  	container_of(_kobj, struct padata_instance, kobj)
  #define attr2pentry(_attr)					\
  	container_of(_attr, struct padata_sysfs_entry, attr)
  
  static void padata_sysfs_release(struct kobject *kobj)
  {
  	struct padata_instance *pinst = kobj2pinst(kobj);
  	__padata_free(pinst);
  }
  
  struct padata_sysfs_entry {
  	struct attribute attr;
  	ssize_t (*show)(struct padata_instance *, struct attribute *, char *);
  	ssize_t (*store)(struct padata_instance *, struct attribute *,
  			 const char *, size_t);
  };
  
  static ssize_t show_cpumask(struct padata_instance *pinst,
  			    struct attribute *attr,  char *buf)
  {
  	struct cpumask *cpumask;
  	ssize_t len;
  
  	mutex_lock(&pinst->lock);
  	if (!strcmp(attr->name, "serial_cpumask"))
  		cpumask = pinst->cpumask.cbcpu;
  	else
  		cpumask = pinst->cpumask.pcpu;

  	len = snprintf(buf, PAGE_SIZE, "%*pb
  ",
  		       nr_cpu_ids, cpumask_bits(cpumask));

  	mutex_unlock(&pinst->lock);

  	return len < PAGE_SIZE ? len : -EINVAL;

  }
  
  static ssize_t store_cpumask(struct padata_instance *pinst,
  			     struct attribute *attr,
  			     const char *buf, size_t count)
  {
  	cpumask_var_t new_cpumask;
  	ssize_t ret;
  	int mask_type;
  
  	if (!alloc_cpumask_var(&new_cpumask, GFP_KERNEL))
  		return -ENOMEM;
  
  	ret = bitmap_parse(buf, count, cpumask_bits(new_cpumask),
  			   nr_cpumask_bits);
  	if (ret < 0)
  		goto out;
  
  	mask_type = !strcmp(attr->name, "serial_cpumask") ?
  		PADATA_CPU_SERIAL : PADATA_CPU_PARALLEL;
  	ret = padata_set_cpumask(pinst, mask_type, new_cpumask);
  	if (!ret)
  		ret = count;
  
  out:
  	free_cpumask_var(new_cpumask);
  	return ret;
  }
  
  #define PADATA_ATTR_RW(_name, _show_name, _store_name)		\
  	static struct padata_sysfs_entry _name##_attr =		\
  		__ATTR(_name, 0644, _show_name, _store_name)
  #define PADATA_ATTR_RO(_name, _show_name)		\
  	static struct padata_sysfs_entry _name##_attr = \
  		__ATTR(_name, 0400, _show_name, NULL)
  
  PADATA_ATTR_RW(serial_cpumask, show_cpumask, store_cpumask);
  PADATA_ATTR_RW(parallel_cpumask, show_cpumask, store_cpumask);
  
  /*
   * Padata sysfs provides the following objects:
   * serial_cpumask   [RW] - cpumask for serial workers
   * parallel_cpumask [RW] - cpumask for parallel workers
   */
  static struct attribute *padata_default_attrs[] = {
  	&serial_cpumask_attr.attr,
  	&parallel_cpumask_attr.attr,
  	NULL,
  };
  
  static ssize_t padata_sysfs_show(struct kobject *kobj,
  				 struct attribute *attr, char *buf)
  {
  	struct padata_instance *pinst;
  	struct padata_sysfs_entry *pentry;
  	ssize_t ret = -EIO;
  
  	pinst = kobj2pinst(kobj);
  	pentry = attr2pentry(attr);
  	if (pentry->show)
  		ret = pentry->show(pinst, attr, buf);
  
  	return ret;
  }
  
  static ssize_t padata_sysfs_store(struct kobject *kobj, struct attribute *attr,
  				  const char *buf, size_t count)
  {
  	struct padata_instance *pinst;
  	struct padata_sysfs_entry *pentry;
  	ssize_t ret = -EIO;
  
  	pinst = kobj2pinst(kobj);
  	pentry = attr2pentry(attr);
  	if (pentry->show)
  		ret = pentry->store(pinst, attr, buf, count);
  
  	return ret;
  }
  
  static const struct sysfs_ops padata_sysfs_ops = {
  	.show = padata_sysfs_show,
  	.store = padata_sysfs_store,
  };
  
  static struct kobj_type padata_attr_type = {
  	.sysfs_ops = &padata_sysfs_ops,
  	.default_attrs = padata_default_attrs,
  	.release = padata_sysfs_release,
  };

  /**

   * padata_alloc - allocate and initialize a padata instance and specify
   *                cpumasks for serial and parallel workers.

   *

   * @wq: workqueue to use for the allocated padata instance

   * @pcpumask: cpumask that will be used for padata parallelization
   * @cbcpumask: cpumask that will be used for padata serialization

   *
   * Must be called from a cpus_read_lock() protected region

   */

  static struct padata_instance *padata_alloc(struct workqueue_struct *wq,
  					    const struct cpumask *pcpumask,
  					    const struct cpumask *cbcpumask)

  {

  	struct padata_instance *pinst;

  	struct parallel_data *pd = NULL;

  
  	pinst = kzalloc(sizeof(struct padata_instance), GFP_KERNEL);
  	if (!pinst)
  		goto err;

  	if (!alloc_cpumask_var(&pinst->cpumask.pcpu, GFP_KERNEL))

  		goto err_free_inst;

  	if (!alloc_cpumask_var(&pinst->cpumask.cbcpu, GFP_KERNEL)) {
  		free_cpumask_var(pinst->cpumask.pcpu);

  		goto err_free_inst;

  	}

  	if (!padata_validate_cpumask(pinst, pcpumask) ||
  	    !padata_validate_cpumask(pinst, cbcpumask))
  		goto err_free_masks;

  	pd = padata_alloc_pd(pinst, pcpumask, cbcpumask);
  	if (!pd)
  		goto err_free_masks;

  	rcu_assign_pointer(pinst->pd, pd);
  
  	pinst->wq = wq;

  	cpumask_copy(pinst->cpumask.pcpu, pcpumask);
  	cpumask_copy(pinst->cpumask.cbcpu, cbcpumask);

  
  	pinst->flags = 0;

  	BLOCKING_INIT_NOTIFIER_HEAD(&pinst->cpumask_change_notifier);

  	kobject_init(&pinst->kobj, &padata_attr_type);

  	mutex_init(&pinst->lock);

  #ifdef CONFIG_HOTPLUG_CPU

  	cpuhp_state_add_instance_nocalls_cpuslocked(hp_online, &pinst->node);

  #endif

  	return pinst;

  err_free_masks:
  	free_cpumask_var(pinst->cpumask.pcpu);
  	free_cpumask_var(pinst->cpumask.cbcpu);

  err_free_inst:
  	kfree(pinst);
  err:
  	return NULL;
  }

  /**

   * padata_alloc_possible - Allocate and initialize padata instance.
   *                         Use the cpu_possible_mask for serial and
   *                         parallel workers.
   *
   * @wq: workqueue to use for the allocated padata instance

   *
   * Must be called from a cpus_read_lock() protected region

   */
  struct padata_instance *padata_alloc_possible(struct workqueue_struct *wq)
  {

  	lockdep_assert_cpus_held();

  	return padata_alloc(wq, cpu_possible_mask, cpu_possible_mask);
  }
  EXPORT_SYMBOL(padata_alloc_possible);
  
  /**

   * padata_free - free a padata instance
   *

   * @padata_inst: padata instance to free

   */
  void padata_free(struct padata_instance *pinst)
  {

  	kobject_put(&pinst->kobj);

  }
  EXPORT_SYMBOL(padata_free);

  
  #ifdef CONFIG_HOTPLUG_CPU
  
  static __init int padata_driver_init(void)
  {
  	int ret;
  
  	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "padata:online",
  				      padata_cpu_online,
  				      padata_cpu_prep_down);
  	if (ret < 0)
  		return ret;
  	hp_online = ret;
  	return 0;
  }
  module_init(padata_driver_init);
  
  static __exit void padata_driver_exit(void)
  {
  	cpuhp_remove_multi_state(hp_online);
  }
  module_exit(padata_driver_exit);
  #endif