/* * padata.c - generic interface to process data streams in parallel * * 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/module.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/rcupdate.h> #define MAX_SEQ_NR INT_MAX - NR_CPUS #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); for (cpu = 0; cpu < cpu_index; cpu++) target_cpu = cpumask_next(target_cpu, pd->cpumask); return target_cpu; } static int padata_cpu_hash(struct padata_priv *padata) { int cpu_index; struct parallel_data *pd; pd = padata->pd; /* * Hash the sequence numbers to the cpus by taking * seq_nr mod. number of cpus in use. */ cpu_index = padata->seq_nr % cpumask_weight(pd->cpumask); return padata_index_to_cpu(pd, cpu_index); } static void padata_parallel_worker(struct work_struct *work) { struct padata_queue *queue; struct parallel_data *pd; struct padata_instance *pinst; LIST_HEAD(local_list); local_bh_disable(); queue = container_of(work, struct padata_queue, pwork); pd = queue->pd; pinst = pd->pinst; spin_lock(&queue->parallel.lock); list_replace_init(&queue->parallel.list, &local_list); spin_unlock(&queue->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 cpumask of padata. * * 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_queue *queue; struct parallel_data *pd; rcu_read_lock_bh(); pd = rcu_dereference(pinst->pd); err = 0; if (!(pinst->flags & PADATA_INIT)) goto out; err = -EBUSY; if ((pinst->flags & PADATA_RESET)) goto out; if (atomic_read(&pd->refcnt) >= MAX_OBJ_NUM) goto out; err = -EINVAL; if (!cpumask_test_cpu(cb_cpu, pd->cpumask)) goto out; err = -EINPROGRESS; atomic_inc(&pd->refcnt); padata->pd = pd; padata->cb_cpu = cb_cpu; if (unlikely(atomic_read(&pd->seq_nr) == pd->max_seq_nr)) atomic_set(&pd->seq_nr, -1); padata->seq_nr = atomic_inc_return(&pd->seq_nr); target_cpu = padata_cpu_hash(padata); queue = per_cpu_ptr(pd->queue, 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->pwork); 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. * * NULL, if all percpu reorder queues are empty. * * -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, empty, calc_seq_nr; int seq_nr, next_nr, overrun, next_overrun; struct padata_queue *queue, *next_queue; struct padata_priv *padata; struct padata_list *reorder; empty = 0; next_nr = -1; next_overrun = 0; next_queue = NULL; num_cpus = cpumask_weight(pd->cpumask); for_each_cpu(cpu, pd->cpumask) { queue = per_cpu_ptr(pd->queue, cpu); reorder = &queue->reorder; /* * Calculate the seq_nr of the object that should be * next in this reorder queue. */ overrun = 0; calc_seq_nr = (atomic_read(&queue->num_obj) * num_cpus) + queue->cpu_index; if (unlikely(calc_seq_nr > pd->max_seq_nr)) { calc_seq_nr = calc_seq_nr - pd->max_seq_nr - 1; overrun = 1; } if (!list_empty(&reorder->list)) { padata = list_entry(reorder->list.next, struct padata_priv, list); seq_nr = padata->seq_nr; BUG_ON(calc_seq_nr != seq_nr); } else { seq_nr = calc_seq_nr; empty++; } if (next_nr < 0 || seq_nr < next_nr || (next_overrun && !overrun)) { next_nr = seq_nr; next_overrun = overrun; next_queue = queue; } } padata = NULL; if (empty == num_cpus) goto out; reorder = &next_queue->reorder; if (!list_empty(&reorder->list)) { padata = list_entry(reorder->list.next, struct padata_priv, list); if (unlikely(next_overrun)) { for_each_cpu(cpu, pd->cpumask) { queue = per_cpu_ptr(pd->queue, cpu); atomic_set(&queue->num_obj, 0); } } spin_lock(&reorder->lock); list_del_init(&padata->list); atomic_dec(&pd->reorder_objects); spin_unlock(&reorder->lock); atomic_inc(&next_queue->num_obj); goto out; } queue = per_cpu_ptr(pd->queue, smp_processor_id()); if (queue->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) { struct padata_priv *padata; struct padata_queue *queue; 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); /* * All reorder queues are empty, or 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 (!padata || 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 imediately. */ if (PTR_ERR(padata) == -ENODATA) { del_timer(&pd->timer); spin_unlock_bh(&pd->lock); return; } queue = per_cpu_ptr(pd->queue, padata->cb_cpu); spin_lock(&queue->serial.lock); list_add_tail(&padata->list, &queue->serial.list); spin_unlock(&queue->serial.lock); queue_work_on(padata->cb_cpu, pinst->wq, &queue->swork); } 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 noone 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 *work) { struct padata_queue *queue; struct parallel_data *pd; LIST_HEAD(local_list); local_bh_disable(); queue = container_of(work, struct padata_queue, swork); pd = queue->pd; spin_lock(&queue->serial.lock); list_replace_init(&queue->serial.list, &local_list); spin_unlock(&queue->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_queue *queue; struct parallel_data *pd; pd = padata->pd; cpu = get_cpu(); queue = per_cpu_ptr(pd->queue, cpu); spin_lock(&queue->reorder.lock); atomic_inc(&pd->reorder_objects); list_add_tail(&padata->list, &queue->reorder.list); spin_unlock(&queue->reorder.lock); put_cpu(); padata_reorder(pd); } EXPORT_SYMBOL(padata_do_serial); /* Allocate and initialize the internal cpumask dependend resources. */ static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst, const struct cpumask *cpumask) { int cpu, cpu_index, num_cpus; struct padata_queue *queue; struct parallel_data *pd; cpu_index = 0; pd = kzalloc(sizeof(struct parallel_data), GFP_KERNEL); if (!pd) goto err; pd->queue = alloc_percpu(struct padata_queue); if (!pd->queue) goto err_free_pd; if (!alloc_cpumask_var(&pd->cpumask, GFP_KERNEL)) goto err_free_queue; cpumask_and(pd->cpumask, cpumask, cpu_active_mask); for_each_cpu(cpu, pd->cpumask) { queue = per_cpu_ptr(pd->queue, cpu); queue->pd = pd; queue->cpu_index = cpu_index; cpu_index++; INIT_LIST_HEAD(&queue->reorder.list); INIT_LIST_HEAD(&queue->parallel.list); INIT_LIST_HEAD(&queue->serial.list); spin_lock_init(&queue->reorder.lock); spin_lock_init(&queue->parallel.lock); spin_lock_init(&queue->serial.lock); INIT_WORK(&queue->pwork, padata_parallel_worker); INIT_WORK(&queue->swork, padata_serial_worker); atomic_set(&queue->num_obj, 0); } num_cpus = cpumask_weight(pd->cpumask); pd->max_seq_nr = (MAX_SEQ_NR / num_cpus) * num_cpus - 1; 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_queue: free_percpu(pd->queue); err_free_pd: kfree(pd); err: return NULL; } static void padata_free_pd(struct parallel_data *pd) { free_cpumask_var(pd->cpumask); free_percpu(pd->queue); kfree(pd); } /* Flush all objects out of the padata queues. */ static void padata_flush_queues(struct parallel_data *pd) { int cpu; struct padata_queue *queue; for_each_cpu(cpu, pd->cpumask) { queue = per_cpu_ptr(pd->queue, cpu); flush_work(&queue->pwork); } del_timer_sync(&pd->timer); if (atomic_read(&pd->reorder_objects)) padata_reorder(pd); for_each_cpu(cpu, pd->cpumask) { queue = per_cpu_ptr(pd->queue, cpu); flush_work(&queue->swork); } BUG_ON(atomic_read(&pd->refcnt) != 0); } /* Replace the internal control stucture with a new one. */ static void padata_replace(struct padata_instance *pinst, struct parallel_data *pd_new) { struct parallel_data *pd_old = pinst->pd; pinst->flags |= PADATA_RESET; rcu_assign_pointer(pinst->pd, pd_new); synchronize_rcu(); padata_flush_queues(pd_old); padata_free_pd(pd_old); pinst->flags &= ~PADATA_RESET; } /** * padata_set_cpumask - set the cpumask that padata should use * * @pinst: padata instance * @cpumask: the cpumask to use */ int padata_set_cpumask(struct padata_instance *pinst, cpumask_var_t cpumask) { struct parallel_data *pd; int err = 0; mutex_lock(&pinst->lock); get_online_cpus(); pd = padata_alloc_pd(pinst, cpumask); if (!pd) { err = -ENOMEM; goto out; } cpumask_copy(pinst->cpumask, cpumask); padata_replace(pinst, pd); out: put_online_cpus(); mutex_unlock(&pinst->lock); return err; } EXPORT_SYMBOL(padata_set_cpumask); static int __padata_add_cpu(struct padata_instance *pinst, int cpu) { struct parallel_data *pd; if (cpumask_test_cpu(cpu, cpu_active_mask)) { pd = padata_alloc_pd(pinst, pinst->cpumask); if (!pd) return -ENOMEM; padata_replace(pinst, pd); } return 0; } /** * padata_add_cpu - add a cpu to the padata cpumask * * @pinst: padata instance * @cpu: cpu to add */ int padata_add_cpu(struct padata_instance *pinst, int cpu) { int err; mutex_lock(&pinst->lock); get_online_cpus(); cpumask_set_cpu(cpu, pinst->cpumask); err = __padata_add_cpu(pinst, cpu); put_online_cpus(); mutex_unlock(&pinst->lock); return err; } EXPORT_SYMBOL(padata_add_cpu); static int __padata_remove_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); if (!pd) return -ENOMEM; padata_replace(pinst, pd); } return 0; } /** * padata_remove_cpu - remove a cpu from the padata cpumask * * @pinst: padata instance * @cpu: cpu to remove */ int padata_remove_cpu(struct padata_instance *pinst, int cpu) { int err; mutex_lock(&pinst->lock); get_online_cpus(); cpumask_clear_cpu(cpu, pinst->cpumask); err = __padata_remove_cpu(pinst, cpu); put_online_cpus(); mutex_unlock(&pinst->lock); return err; } EXPORT_SYMBOL(padata_remove_cpu); /** * padata_start - start the parallel processing * * @pinst: padata instance to start */ void padata_start(struct padata_instance *pinst) { mutex_lock(&pinst->lock); pinst->flags |= PADATA_INIT; mutex_unlock(&pinst->lock); } 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); pinst->flags &= ~PADATA_INIT; mutex_unlock(&pinst->lock); } EXPORT_SYMBOL(padata_stop); #ifdef CONFIG_HOTPLUG_CPU static int padata_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) { int err; struct padata_instance *pinst; int cpu = (unsigned long)hcpu; pinst = container_of(nfb, struct padata_instance, cpu_notifier); switch (action) { case CPU_ONLINE: case CPU_ONLINE_FROZEN: if (!cpumask_test_cpu(cpu, pinst->cpumask)) break; mutex_lock(&pinst->lock); err = __padata_add_cpu(pinst, cpu); mutex_unlock(&pinst->lock); if (err) return notifier_from_errno(err); break; case CPU_DOWN_PREPARE: case CPU_DOWN_PREPARE_FROZEN: if (!cpumask_test_cpu(cpu, pinst->cpumask)) break; mutex_lock(&pinst->lock); err = __padata_remove_cpu(pinst, cpu); mutex_unlock(&pinst->lock); if (err) return notifier_from_errno(err); break; case CPU_UP_CANCELED: case CPU_UP_CANCELED_FROZEN: if (!cpumask_test_cpu(cpu, pinst->cpumask)) break; mutex_lock(&pinst->lock); __padata_remove_cpu(pinst, cpu); mutex_unlock(&pinst->lock); case CPU_DOWN_FAILED: case CPU_DOWN_FAILED_FROZEN: if (!cpumask_test_cpu(cpu, pinst->cpumask)) break; mutex_lock(&pinst->lock); __padata_add_cpu(pinst, cpu); mutex_unlock(&pinst->lock); } return NOTIFY_OK; } #endif /** * padata_alloc - allocate and initialize a padata instance * * @cpumask: cpumask that padata uses for parallelization * @wq: workqueue to use for the allocated padata instance */ struct padata_instance *padata_alloc(const struct cpumask *cpumask, struct workqueue_struct *wq) { struct padata_instance *pinst; struct parallel_data *pd; pinst = kzalloc(sizeof(struct padata_instance), GFP_KERNEL); if (!pinst) goto err; get_online_cpus(); pd = padata_alloc_pd(pinst, cpumask); if (!pd) goto err_free_inst; if (!alloc_cpumask_var(&pinst->cpumask, GFP_KERNEL)) goto err_free_pd; rcu_assign_pointer(pinst->pd, pd); pinst->wq = wq; cpumask_copy(pinst->cpumask, cpumask); pinst->flags = 0; #ifdef CONFIG_HOTPLUG_CPU pinst->cpu_notifier.notifier_call = padata_cpu_callback; pinst->cpu_notifier.priority = 0; register_hotcpu_notifier(&pinst->cpu_notifier); #endif put_online_cpus(); mutex_init(&pinst->lock); return pinst; err_free_pd: padata_free_pd(pd); err_free_inst: kfree(pinst); put_online_cpus(); err: return NULL; } EXPORT_SYMBOL(padata_alloc); /** * padata_free - free a padata instance * * @padata_inst: padata instance to free */ void padata_free(struct padata_instance *pinst) { padata_stop(pinst); synchronize_rcu(); #ifdef CONFIG_HOTPLUG_CPU unregister_hotcpu_notifier(&pinst->cpu_notifier); #endif get_online_cpus(); padata_flush_queues(pinst->pd); put_online_cpus(); padata_free_pd(pinst->pd); free_cpumask_var(pinst->cpumask); kfree(pinst); } EXPORT_SYMBOL(padata_free);