1 files changed, 194 insertions, 192 deletions

diff --git a/kernel/padata.c b/kernel/padata.c
index c3fec1413295..72777c10bb9c 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -2,7 +2,7 @@
 /*
  * padata.c - generic interface to process data streams in parallel
  *
- * See Documentation/padata.txt for an api documentation.
+ * See Documentation/core-api/padata.rst for more information.
  *
  * Copyright (C) 2008, 2009 secunet Security Networks AG
  * Copyright (C) 2008, 2009 Steffen Klassert <steffen.klassert@secunet.com>
@@ -35,6 +35,8 @@
 
 #define MAX_OBJ_NUM 1000
 
+static void padata_free_pd(struct parallel_data *pd);
+
 static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index)
 {
 	int cpu, target_cpu;
@@ -87,7 +89,7 @@ static void padata_parallel_worker(struct work_struct *parallel_work)
 /**
  * padata_do_parallel - padata parallelization function
  *
- * @pinst: padata instance
+ * @ps: padatashell
  * @padata: object to be parallelized
  * @cb_cpu: pointer to the CPU that the serialization callback function should
  *          run on.  If it's not in the serial cpumask of @pinst
@@ -97,17 +99,20 @@ static void padata_parallel_worker(struct work_struct *parallel_work)
  * 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.
+ *
+ * Return: 0 on success or else negative error code.
  */
-int padata_do_parallel(struct padata_instance *pinst,
+int padata_do_parallel(struct padata_shell *ps,
 		       struct padata_priv *padata, int *cb_cpu)
 {
+	struct padata_instance *pinst = ps->pinst;
 	int i, cpu, cpu_index, target_cpu, err;
 	struct padata_parallel_queue *queue;
 	struct parallel_data *pd;
 
 	rcu_read_lock_bh();
 
-	pd = rcu_dereference_bh(pinst->pd);
+	pd = rcu_dereference_bh(ps->pd);
 
 	err = -EINVAL;
 	if (!(pinst->flags & PADATA_INIT) || pinst->flags & PADATA_INVALID)
@@ -160,14 +165,12 @@ EXPORT_SYMBOL(padata_do_parallel);
 /*
  * padata_find_next - Find 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.
- *
- * NULL, 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.
+ * Return:
+ * * A pointer to the control struct of the next object that needs
+ *   serialization, if present in one of the percpu reorder queues.
+ * * NULL, 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.
  */
 static struct padata_priv *padata_find_next(struct parallel_data *pd,
 					    bool remove_object)
@@ -199,7 +202,6 @@ static struct padata_priv *padata_find_next(struct parallel_data *pd,
 
 	if (remove_object) {
 		list_del_init(&padata->list);
-		atomic_dec(&pd->reorder_objects);
 		++pd->processed;
 		pd->cpu = cpumask_next_wrap(cpu, pd->cpumask.pcpu, -1, false);
 	}
@@ -210,10 +212,10 @@ static struct padata_priv *padata_find_next(struct parallel_data *pd,
 
 static void padata_reorder(struct parallel_data *pd)
 {
+	struct padata_instance *pinst = pd->ps->pinst;
 	int cb_cpu;
 	struct padata_priv *padata;
 	struct padata_serial_queue *squeue;
-	struct padata_instance *pinst = pd->pinst;
 	struct padata_parallel_queue *next_queue;
 
 	/*
@@ -283,6 +285,7 @@ static void padata_serial_worker(struct work_struct *serial_work)
 	struct padata_serial_queue *squeue;
 	struct parallel_data *pd;
 	LIST_HEAD(local_list);
+	int cnt;
 
 	local_bh_disable();
 	squeue = container_of(serial_work, struct padata_serial_queue, work);
@@ -292,6 +295,8 @@ static void padata_serial_worker(struct work_struct *serial_work)
 	list_replace_init(&squeue->serial.list, &local_list);
 	spin_unlock(&squeue->serial.lock);
 
+	cnt = 0;
+
 	while (!list_empty(&local_list)) {
 		struct padata_priv *padata;
 
@@ -301,9 +306,12 @@ static void padata_serial_worker(struct work_struct *serial_work)
 		list_del_init(&padata->list);
 
 		padata->serial(padata);
-		atomic_dec(&pd->refcnt);
+		cnt++;
 	}
 	local_bh_enable();
+
+	if (atomic_sub_and_test(cnt, &pd->refcnt))
+		padata_free_pd(pd);
 }
 
 /**
@@ -327,7 +335,6 @@ void padata_do_serial(struct padata_priv *padata)
 		if (cur->seq_nr < padata->seq_nr)
 			break;
 	list_add(&padata->list, &cur->list);
-	atomic_inc(&pd->reorder_objects);
 	spin_unlock(&pqueue->reorder.lock);
 
 	/*
@@ -341,36 +348,39 @@ void padata_do_serial(struct padata_priv *padata)
 }
 EXPORT_SYMBOL(padata_do_serial);
 
-static int padata_setup_cpumasks(struct parallel_data *pd,
-				 const struct cpumask *pcpumask,
-				 const struct cpumask *cbcpumask)
+static int padata_setup_cpumasks(struct padata_instance *pinst)
 {
 	struct workqueue_attrs *attrs;
+	int err;
+
+	attrs = alloc_workqueue_attrs();
+	if (!attrs)
+		return -ENOMEM;
+
+	/* Restrict parallel_wq workers to pd->cpumask.pcpu. */
+	cpumask_copy(attrs->cpumask, pinst->cpumask.pcpu);
+	err = apply_workqueue_attrs(pinst->parallel_wq, attrs);
+	free_workqueue_attrs(attrs);
+
+	return err;
+}
+
+static int pd_setup_cpumasks(struct parallel_data *pd,
+			     const struct cpumask *pcpumask,
+			     const struct cpumask *cbcpumask)
+{
 	int err = -ENOMEM;
 
 	if (!alloc_cpumask_var(&pd->cpumask.pcpu, GFP_KERNEL))
 		goto out;
-	cpumask_and(pd->cpumask.pcpu, pcpumask, cpu_online_mask);
-
 	if (!alloc_cpumask_var(&pd->cpumask.cbcpu, GFP_KERNEL))
 		goto free_pcpu_mask;
-	cpumask_and(pd->cpumask.cbcpu, cbcpumask, cpu_online_mask);
 
-	attrs = alloc_workqueue_attrs();
-	if (!attrs)
-		goto free_cbcpu_mask;
-
-	/* Restrict parallel_wq workers to pd->cpumask.pcpu. */
-	cpumask_copy(attrs->cpumask, pd->cpumask.pcpu);
-	err = apply_workqueue_attrs(pd->pinst->parallel_wq, attrs);
-	free_workqueue_attrs(attrs);
-	if (err < 0)
-		goto free_cbcpu_mask;
+	cpumask_copy(pd->cpumask.pcpu, pcpumask);
+	cpumask_copy(pd->cpumask.cbcpu, cbcpumask);
 
 	return 0;
 
-free_cbcpu_mask:
-	free_cpumask_var(pd->cpumask.cbcpu);
 free_pcpu_mask:
 	free_cpumask_var(pd->cpumask.pcpu);
 out:
@@ -414,12 +424,16 @@ static void padata_init_pqueues(struct parallel_data *pd)
 }
 
 /* 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)
+static struct parallel_data *padata_alloc_pd(struct padata_shell *ps)
 {
+	struct padata_instance *pinst = ps->pinst;
+	const struct cpumask *cbcpumask;
+	const struct cpumask *pcpumask;
 	struct parallel_data *pd;
 
+	cbcpumask = pinst->rcpumask.cbcpu;
+	pcpumask = pinst->rcpumask.pcpu;
+
 	pd = kzalloc(sizeof(struct parallel_data), GFP_KERNEL);
 	if (!pd)
 		goto err;
@@ -432,15 +446,14 @@ static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst,
 	if (!pd->squeue)
 		goto err_free_pqueue;
 
-	pd->pinst = pinst;
-	if (padata_setup_cpumasks(pd, pcpumask, cbcpumask) < 0)
+	pd->ps = ps;
+	if (pd_setup_cpumasks(pd, pcpumask, cbcpumask))
 		goto err_free_squeue;
 
 	padata_init_pqueues(pd);
 	padata_init_squeues(pd);
 	atomic_set(&pd->seq_nr, -1);
-	atomic_set(&pd->reorder_objects, 0);
-	atomic_set(&pd->refcnt, 0);
+	atomic_set(&pd->refcnt, 1);
 	spin_lock_init(&pd->lock);
 	pd->cpu = cpumask_first(pd->cpumask.pcpu);
 	INIT_WORK(&pd->reorder_work, invoke_padata_reorder);
@@ -466,29 +479,6 @@ static void padata_free_pd(struct parallel_data *pd)
 	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);
-	}
-
-	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;
@@ -502,72 +492,52 @@ static void __padata_stop(struct padata_instance *pinst)
 	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)
+static int padata_replace_one(struct padata_shell *ps)
+{
+	struct parallel_data *pd_new;
+
+	pd_new = padata_alloc_pd(ps);
+	if (!pd_new)
+		return -ENOMEM;
+
+	ps->opd = rcu_dereference_protected(ps->pd, 1);
+	rcu_assign_pointer(ps->pd, pd_new);
+
+	return 0;
+}
+
+static int padata_replace(struct padata_instance *pinst)
 {
-	struct parallel_data *pd_old = pinst->pd;
-	int notification_mask = 0;
+	struct padata_shell *ps;
+	int err;
 
 	pinst->flags |= PADATA_RESET;
 
-	rcu_assign_pointer(pinst->pd, pd_new);
+	cpumask_and(pinst->rcpumask.pcpu, pinst->cpumask.pcpu,
+		    cpu_online_mask);
 
-	synchronize_rcu();
+	cpumask_and(pinst->rcpumask.cbcpu, pinst->cpumask.cbcpu,
+		    cpu_online_mask);
 
-	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;
+	list_for_each_entry(ps, &pinst->pslist, list) {
+		err = padata_replace_one(ps);
+		if (err)
+			break;
+	}
 
-	padata_flush_queues(pd_old);
-	padata_free_pd(pd_old);
+	synchronize_rcu();
 
-	if (notification_mask)
-		blocking_notifier_call_chain(&pinst->cpumask_change_notifier,
-					     notification_mask,
-					     &pd_new->cpumask);
+	list_for_each_entry_continue_reverse(ps, &pinst->pslist, list)
+		if (atomic_dec_and_test(&ps->opd->refcnt))
+			padata_free_pd(ps->opd);
 
 	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);
+	return err;
 }
-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,
@@ -587,7 +557,7 @@ static int __padata_set_cpumasks(struct padata_instance *pinst,
 				 cpumask_var_t cbcpumask)
 {
 	int valid;
-	struct parallel_data *pd;
+	int err;
 
 	valid = padata_validate_cpumask(pinst, pcpumask);
 	if (!valid) {
@@ -600,29 +570,26 @@ static int __padata_set_cpumasks(struct padata_instance *pinst,
 		__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);
+	err = padata_setup_cpumasks(pinst) ?: padata_replace(pinst);
 
 	if (valid)
 		__padata_start(pinst);
 
-	return 0;
+	return err;
 }
 
 /**
- * padata_set_cpumask: Sets specified by @cpumask_type cpumask to the value
- *                     equivalent to @cpumask.
- *
+ * 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
+ *
+ * Return: 0 on success or negative error code
  */
 int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type,
 		       cpumask_var_t cpumask)
@@ -630,8 +597,8 @@ int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type,
 	struct cpumask *serial_mask, *parallel_mask;
 	int err = -EINVAL;
 
-	mutex_lock(&pinst->lock);
 	get_online_cpus();
+	mutex_lock(&pinst->lock);
 
 	switch (cpumask_type) {
 	case PADATA_CPU_PARALLEL:
@@ -649,8 +616,8 @@ int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type,
 	err =  __padata_set_cpumasks(pinst, parallel_mask, serial_mask);
 
 out:
-	put_online_cpus();
 	mutex_unlock(&pinst->lock);
+	put_online_cpus();
 
 	return err;
 }
@@ -660,6 +627,8 @@ EXPORT_SYMBOL(padata_set_cpumask);
  * padata_start - start the parallel processing
  *
  * @pinst: padata instance to start
+ *
+ * Return: 0 on success or negative error code
  */
 int padata_start(struct padata_instance *pinst)
 {
@@ -695,82 +664,33 @@ EXPORT_SYMBOL(padata_stop);
 
 static int __padata_add_cpu(struct padata_instance *pinst, int cpu)
 {
-	struct parallel_data *pd;
+	int err = 0;
 
 	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);
+		err = padata_replace(pinst);
 
 		if (padata_validate_cpumask(pinst, pinst->cpumask.pcpu) &&
 		    padata_validate_cpumask(pinst, pinst->cpumask.cbcpu))
 			__padata_start(pinst);
 	}
 
-	return 0;
+	return err;
 }
 
 static int __padata_remove_cpu(struct padata_instance *pinst, int cpu)
 {
-	struct parallel_data *pd = NULL;
-
-	if (cpumask_test_cpu(cpu, cpu_online_mask)) {
+	int err = 0;
 
+	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);
+		err = padata_replace(pinst);
 	}
 
-	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)
 {
@@ -793,7 +713,7 @@ static int padata_cpu_online(unsigned int cpu, struct hlist_node *node)
 	return ret;
 }
 
-static int padata_cpu_prep_down(unsigned int cpu, struct hlist_node *node)
+static int padata_cpu_dead(unsigned int cpu, struct hlist_node *node)
 {
 	struct padata_instance *pinst;
 	int ret;
@@ -814,11 +734,15 @@ static enum cpuhp_state hp_online;
 static void __padata_free(struct padata_instance *pinst)
 {
 #ifdef CONFIG_HOTPLUG_CPU
+	cpuhp_state_remove_instance_nocalls(CPUHP_PADATA_DEAD, &pinst->node);
 	cpuhp_state_remove_instance_nocalls(hp_online, &pinst->node);
 #endif
 
+	WARN_ON(!list_empty(&pinst->pslist));
+
 	padata_stop(pinst);
-	padata_free_pd(pinst->pd);
+	free_cpumask_var(pinst->rcpumask.cbcpu);
+	free_cpumask_var(pinst->rcpumask.pcpu);
 	free_cpumask_var(pinst->cpumask.pcpu);
 	free_cpumask_var(pinst->cpumask.cbcpu);
 	destroy_workqueue(pinst->serial_wq);
@@ -959,13 +883,14 @@ static struct kobj_type padata_attr_type = {
  * @name: used to identify the instance
  * @pcpumask: cpumask that will be used for padata parallelization
  * @cbcpumask: cpumask that will be used for padata serialization
+ *
+ * Return: new instance on success, NULL on error
  */
 static struct padata_instance *padata_alloc(const char *name,
 					    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)
@@ -993,29 +918,40 @@ static struct padata_instance *padata_alloc(const char *name,
 	    !padata_validate_cpumask(pinst, cbcpumask))
 		goto err_free_masks;
 
-	pd = padata_alloc_pd(pinst, pcpumask, cbcpumask);
-	if (!pd)
+	if (!alloc_cpumask_var(&pinst->rcpumask.pcpu, GFP_KERNEL))
 		goto err_free_masks;
+	if (!alloc_cpumask_var(&pinst->rcpumask.cbcpu, GFP_KERNEL))
+		goto err_free_rcpumask_pcpu;
 
-	rcu_assign_pointer(pinst->pd, pd);
+	INIT_LIST_HEAD(&pinst->pslist);
 
 	cpumask_copy(pinst->cpumask.pcpu, pcpumask);
 	cpumask_copy(pinst->cpumask.cbcpu, cbcpumask);
+	cpumask_and(pinst->rcpumask.pcpu, pcpumask, cpu_online_mask);
+	cpumask_and(pinst->rcpumask.cbcpu, cbcpumask, cpu_online_mask);
+
+	if (padata_setup_cpumasks(pinst))
+		goto err_free_rcpumask_cbcpu;
 
 	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);
+	cpuhp_state_add_instance_nocalls_cpuslocked(CPUHP_PADATA_DEAD,
+						    &pinst->node);
 #endif
 
 	put_online_cpus();
 
 	return pinst;
 
+err_free_rcpumask_cbcpu:
+	free_cpumask_var(pinst->rcpumask.cbcpu);
+err_free_rcpumask_pcpu:
+	free_cpumask_var(pinst->rcpumask.pcpu);
 err_free_masks:
 	free_cpumask_var(pinst->cpumask.pcpu);
 	free_cpumask_var(pinst->cpumask.cbcpu);
@@ -1036,6 +972,8 @@ err:
  *                         parallel workers.
  *
  * @name: used to identify the instance
+ *
+ * Return: new instance on success, NULL on error
  */
 struct padata_instance *padata_alloc_possible(const char *name)
 {
@@ -1046,7 +984,7 @@ EXPORT_SYMBOL(padata_alloc_possible);
 /**
  * padata_free - free a padata instance
  *
- * @padata_inst: padata instance to free
+ * @pinst: padata instance to free
  */
 void padata_free(struct padata_instance *pinst)
 {
@@ -1054,6 +992,63 @@ void padata_free(struct padata_instance *pinst)
 }
 EXPORT_SYMBOL(padata_free);
 
+/**
+ * padata_alloc_shell - Allocate and initialize padata shell.
+ *
+ * @pinst: Parent padata_instance object.
+ *
+ * Return: new shell on success, NULL on error
+ */
+struct padata_shell *padata_alloc_shell(struct padata_instance *pinst)
+{
+	struct parallel_data *pd;
+	struct padata_shell *ps;
+
+	ps = kzalloc(sizeof(*ps), GFP_KERNEL);
+	if (!ps)
+		goto out;
+
+	ps->pinst = pinst;
+
+	get_online_cpus();
+	pd = padata_alloc_pd(ps);
+	put_online_cpus();
+
+	if (!pd)
+		goto out_free_ps;
+
+	mutex_lock(&pinst->lock);
+	RCU_INIT_POINTER(ps->pd, pd);
+	list_add(&ps->list, &pinst->pslist);
+	mutex_unlock(&pinst->lock);
+
+	return ps;
+
+out_free_ps:
+	kfree(ps);
+out:
+	return NULL;
+}
+EXPORT_SYMBOL(padata_alloc_shell);
+
+/**
+ * padata_free_shell - free a padata shell
+ *
+ * @ps: padata shell to free
+ */
+void padata_free_shell(struct padata_shell *ps)
+{
+	struct padata_instance *pinst = ps->pinst;
+
+	mutex_lock(&pinst->lock);
+	list_del(&ps->list);
+	padata_free_pd(rcu_dereference_protected(ps->pd, 1));
+	mutex_unlock(&pinst->lock);
+
+	kfree(ps);
+}
+EXPORT_SYMBOL(padata_free_shell);
+
 #ifdef CONFIG_HOTPLUG_CPU
 
 static __init int padata_driver_init(void)
@@ -1061,17 +1056,24 @@ 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);
+				      padata_cpu_online, NULL);
 	if (ret < 0)
 		return ret;
 	hp_online = ret;
+
+	ret = cpuhp_setup_state_multi(CPUHP_PADATA_DEAD, "padata:dead",
+				      NULL, padata_cpu_dead);
+	if (ret < 0) {
+		cpuhp_remove_multi_state(hp_online);
+		return ret;
+	}
 	return 0;
 }
 module_init(padata_driver_init);
 
 static __exit void padata_driver_exit(void)
 {
+	cpuhp_remove_multi_state(CPUHP_PADATA_DEAD);
 	cpuhp_remove_multi_state(hp_online);
 }
 module_exit(padata_driver_exit);