![Steffen Klassert](/assets/img/avatar_default.png)
padata_get_next needs to check whether the next object that need serialization must be parallel processed by the local cpu. This check was wrong implemented and returned always true, so the try_again loop in padata_reorder was never taken. This can lead to object leaks in some rare cases due to a race that appears with the trylock in padata_reorder. The try_again loop was not a good idea after all, because a cpu could take that loop frequently, so we handle this with a timer instead. This patch adds a timer to handle the race that appears with the trylock. If cpu1 queues an object to the reorder queue while cpu2 holds the pd->lock but left the while loop in padata_reorder already, cpu2 can't care for this object and cpu1 exits because it can't get the lock. Usually the next cpu that takes the lock cares for this object too. We need the timer just if this object was the last one that arrives to the reorder queues. The timer function sends it out in this case. Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
709 lines
15 KiB
C
709 lines
15 KiB
C
/*
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* padata.c - generic interface to process data streams in parallel
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*
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* Copyright (C) 2008, 2009 secunet Security Networks AG
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* Copyright (C) 2008, 2009 Steffen Klassert <steffen.klassert@secunet.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <linux/module.h>
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#include <linux/cpumask.h>
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#include <linux/err.h>
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#include <linux/cpu.h>
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#include <linux/padata.h>
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#include <linux/mutex.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/rcupdate.h>
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#define MAX_SEQ_NR INT_MAX - NR_CPUS
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#define MAX_OBJ_NUM 1000
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static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index)
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{
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int cpu, target_cpu;
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target_cpu = cpumask_first(pd->cpumask);
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for (cpu = 0; cpu < cpu_index; cpu++)
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target_cpu = cpumask_next(target_cpu, pd->cpumask);
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return target_cpu;
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}
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static int padata_cpu_hash(struct padata_priv *padata)
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{
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int cpu_index;
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struct parallel_data *pd;
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pd = padata->pd;
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/*
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* Hash the sequence numbers to the cpus by taking
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* seq_nr mod. number of cpus in use.
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*/
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cpu_index = padata->seq_nr % cpumask_weight(pd->cpumask);
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return padata_index_to_cpu(pd, cpu_index);
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}
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static void padata_parallel_worker(struct work_struct *work)
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{
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struct padata_queue *queue;
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struct parallel_data *pd;
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struct padata_instance *pinst;
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LIST_HEAD(local_list);
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local_bh_disable();
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queue = container_of(work, struct padata_queue, pwork);
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pd = queue->pd;
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pinst = pd->pinst;
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spin_lock(&queue->parallel.lock);
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list_replace_init(&queue->parallel.list, &local_list);
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spin_unlock(&queue->parallel.lock);
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while (!list_empty(&local_list)) {
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struct padata_priv *padata;
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padata = list_entry(local_list.next,
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struct padata_priv, list);
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list_del_init(&padata->list);
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padata->parallel(padata);
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}
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local_bh_enable();
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}
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/*
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* padata_do_parallel - padata parallelization function
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*
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* @pinst: padata instance
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* @padata: object to be parallelized
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* @cb_cpu: cpu the serialization callback function will run on,
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* must be in the cpumask of padata.
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*
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* The parallelization callback function will run with BHs off.
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* Note: Every object which is parallelized by padata_do_parallel
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* must be seen by padata_do_serial.
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*/
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int padata_do_parallel(struct padata_instance *pinst,
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struct padata_priv *padata, int cb_cpu)
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{
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int target_cpu, err;
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struct padata_queue *queue;
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struct parallel_data *pd;
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rcu_read_lock_bh();
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pd = rcu_dereference(pinst->pd);
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err = 0;
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if (!(pinst->flags & PADATA_INIT))
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goto out;
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err = -EBUSY;
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if ((pinst->flags & PADATA_RESET))
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goto out;
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if (atomic_read(&pd->refcnt) >= MAX_OBJ_NUM)
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goto out;
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err = -EINVAL;
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if (!cpumask_test_cpu(cb_cpu, pd->cpumask))
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goto out;
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err = -EINPROGRESS;
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atomic_inc(&pd->refcnt);
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padata->pd = pd;
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padata->cb_cpu = cb_cpu;
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if (unlikely(atomic_read(&pd->seq_nr) == pd->max_seq_nr))
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atomic_set(&pd->seq_nr, -1);
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padata->seq_nr = atomic_inc_return(&pd->seq_nr);
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target_cpu = padata_cpu_hash(padata);
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queue = per_cpu_ptr(pd->queue, target_cpu);
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spin_lock(&queue->parallel.lock);
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list_add_tail(&padata->list, &queue->parallel.list);
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spin_unlock(&queue->parallel.lock);
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queue_work_on(target_cpu, pinst->wq, &queue->pwork);
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out:
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rcu_read_unlock_bh();
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return err;
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}
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EXPORT_SYMBOL(padata_do_parallel);
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static struct padata_priv *padata_get_next(struct parallel_data *pd)
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{
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int cpu, num_cpus, empty, calc_seq_nr;
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int seq_nr, next_nr, overrun, next_overrun;
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struct padata_queue *queue, *next_queue;
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struct padata_priv *padata;
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struct padata_list *reorder;
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empty = 0;
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next_nr = -1;
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next_overrun = 0;
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next_queue = NULL;
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num_cpus = cpumask_weight(pd->cpumask);
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for_each_cpu(cpu, pd->cpumask) {
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queue = per_cpu_ptr(pd->queue, cpu);
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reorder = &queue->reorder;
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/*
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* Calculate the seq_nr of the object that should be
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* next in this queue.
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*/
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overrun = 0;
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calc_seq_nr = (atomic_read(&queue->num_obj) * num_cpus)
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+ queue->cpu_index;
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if (unlikely(calc_seq_nr > pd->max_seq_nr)) {
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calc_seq_nr = calc_seq_nr - pd->max_seq_nr - 1;
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overrun = 1;
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}
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if (!list_empty(&reorder->list)) {
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padata = list_entry(reorder->list.next,
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struct padata_priv, list);
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seq_nr = padata->seq_nr;
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BUG_ON(calc_seq_nr != seq_nr);
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} else {
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seq_nr = calc_seq_nr;
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empty++;
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}
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if (next_nr < 0 || seq_nr < next_nr
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|| (next_overrun && !overrun)) {
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next_nr = seq_nr;
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next_overrun = overrun;
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next_queue = queue;
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}
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}
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padata = NULL;
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if (empty == num_cpus)
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goto out;
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reorder = &next_queue->reorder;
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if (!list_empty(&reorder->list)) {
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padata = list_entry(reorder->list.next,
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struct padata_priv, list);
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if (unlikely(next_overrun)) {
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for_each_cpu(cpu, pd->cpumask) {
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queue = per_cpu_ptr(pd->queue, cpu);
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atomic_set(&queue->num_obj, 0);
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}
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}
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spin_lock(&reorder->lock);
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list_del_init(&padata->list);
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atomic_dec(&pd->reorder_objects);
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spin_unlock(&reorder->lock);
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atomic_inc(&next_queue->num_obj);
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goto out;
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}
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queue = per_cpu_ptr(pd->queue, smp_processor_id());
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if (queue->cpu_index == next_queue->cpu_index) {
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padata = ERR_PTR(-ENODATA);
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goto out;
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}
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padata = ERR_PTR(-EINPROGRESS);
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out:
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return padata;
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}
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static void padata_reorder(struct parallel_data *pd)
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{
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struct padata_priv *padata;
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struct padata_queue *queue;
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struct padata_instance *pinst = pd->pinst;
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if (!spin_trylock_bh(&pd->lock))
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return;
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while (1) {
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padata = padata_get_next(pd);
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if (!padata || PTR_ERR(padata) == -EINPROGRESS)
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break;
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if (PTR_ERR(padata) == -ENODATA) {
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del_timer(&pd->timer);
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spin_unlock_bh(&pd->lock);
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return;
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}
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queue = per_cpu_ptr(pd->queue, padata->cb_cpu);
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spin_lock(&queue->serial.lock);
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list_add_tail(&padata->list, &queue->serial.list);
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spin_unlock(&queue->serial.lock);
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queue_work_on(padata->cb_cpu, pinst->wq, &queue->swork);
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}
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spin_unlock_bh(&pd->lock);
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if (atomic_read(&pd->reorder_objects)
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&& !(pinst->flags & PADATA_RESET))
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mod_timer(&pd->timer, jiffies + HZ);
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else
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del_timer(&pd->timer);
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return;
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}
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static void padata_reorder_timer(unsigned long arg)
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{
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struct parallel_data *pd = (struct parallel_data *)arg;
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padata_reorder(pd);
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}
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static void padata_serial_worker(struct work_struct *work)
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{
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struct padata_queue *queue;
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struct parallel_data *pd;
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LIST_HEAD(local_list);
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local_bh_disable();
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queue = container_of(work, struct padata_queue, swork);
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pd = queue->pd;
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spin_lock(&queue->serial.lock);
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list_replace_init(&queue->serial.list, &local_list);
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spin_unlock(&queue->serial.lock);
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while (!list_empty(&local_list)) {
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struct padata_priv *padata;
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padata = list_entry(local_list.next,
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struct padata_priv, list);
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list_del_init(&padata->list);
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padata->serial(padata);
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atomic_dec(&pd->refcnt);
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}
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local_bh_enable();
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}
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/*
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* padata_do_serial - padata serialization function
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*
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* @padata: object to be serialized.
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*
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* padata_do_serial must be called for every parallelized object.
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* The serialization callback function will run with BHs off.
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*/
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void padata_do_serial(struct padata_priv *padata)
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{
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int cpu;
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struct padata_queue *queue;
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struct parallel_data *pd;
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pd = padata->pd;
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cpu = get_cpu();
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queue = per_cpu_ptr(pd->queue, cpu);
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spin_lock(&queue->reorder.lock);
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atomic_inc(&pd->reorder_objects);
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list_add_tail(&padata->list, &queue->reorder.list);
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spin_unlock(&queue->reorder.lock);
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put_cpu();
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padata_reorder(pd);
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}
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EXPORT_SYMBOL(padata_do_serial);
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static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst,
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const struct cpumask *cpumask)
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{
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int cpu, cpu_index, num_cpus;
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struct padata_queue *queue;
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struct parallel_data *pd;
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cpu_index = 0;
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pd = kzalloc(sizeof(struct parallel_data), GFP_KERNEL);
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if (!pd)
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goto err;
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pd->queue = alloc_percpu(struct padata_queue);
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if (!pd->queue)
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goto err_free_pd;
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if (!alloc_cpumask_var(&pd->cpumask, GFP_KERNEL))
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goto err_free_queue;
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cpumask_and(pd->cpumask, cpumask, cpu_active_mask);
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for_each_cpu(cpu, pd->cpumask) {
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queue = per_cpu_ptr(pd->queue, cpu);
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queue->pd = pd;
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queue->cpu_index = cpu_index;
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cpu_index++;
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INIT_LIST_HEAD(&queue->reorder.list);
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INIT_LIST_HEAD(&queue->parallel.list);
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INIT_LIST_HEAD(&queue->serial.list);
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spin_lock_init(&queue->reorder.lock);
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spin_lock_init(&queue->parallel.lock);
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spin_lock_init(&queue->serial.lock);
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INIT_WORK(&queue->pwork, padata_parallel_worker);
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INIT_WORK(&queue->swork, padata_serial_worker);
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atomic_set(&queue->num_obj, 0);
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}
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num_cpus = cpumask_weight(pd->cpumask);
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pd->max_seq_nr = (MAX_SEQ_NR / num_cpus) * num_cpus - 1;
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setup_timer(&pd->timer, padata_reorder_timer, (unsigned long)pd);
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atomic_set(&pd->seq_nr, -1);
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atomic_set(&pd->reorder_objects, 0);
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atomic_set(&pd->refcnt, 0);
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pd->pinst = pinst;
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spin_lock_init(&pd->lock);
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return pd;
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err_free_queue:
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free_percpu(pd->queue);
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err_free_pd:
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kfree(pd);
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err:
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return NULL;
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}
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static void padata_free_pd(struct parallel_data *pd)
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{
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free_cpumask_var(pd->cpumask);
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free_percpu(pd->queue);
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kfree(pd);
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}
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static void padata_replace(struct padata_instance *pinst,
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struct parallel_data *pd_new)
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{
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struct parallel_data *pd_old = pinst->pd;
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pinst->flags |= PADATA_RESET;
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rcu_assign_pointer(pinst->pd, pd_new);
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synchronize_rcu();
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while (atomic_read(&pd_old->refcnt) != 0)
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yield();
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flush_workqueue(pinst->wq);
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padata_free_pd(pd_old);
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pinst->flags &= ~PADATA_RESET;
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}
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/*
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* padata_set_cpumask - set the cpumask that padata should use
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*
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* @pinst: padata instance
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* @cpumask: the cpumask to use
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*/
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int padata_set_cpumask(struct padata_instance *pinst,
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cpumask_var_t cpumask)
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{
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struct parallel_data *pd;
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int err = 0;
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mutex_lock(&pinst->lock);
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get_online_cpus();
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pd = padata_alloc_pd(pinst, cpumask);
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if (!pd) {
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err = -ENOMEM;
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goto out;
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}
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cpumask_copy(pinst->cpumask, cpumask);
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padata_replace(pinst, pd);
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out:
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put_online_cpus();
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mutex_unlock(&pinst->lock);
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return err;
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}
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EXPORT_SYMBOL(padata_set_cpumask);
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static int __padata_add_cpu(struct padata_instance *pinst, int cpu)
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{
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struct parallel_data *pd;
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if (cpumask_test_cpu(cpu, cpu_active_mask)) {
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pd = padata_alloc_pd(pinst, pinst->cpumask);
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if (!pd)
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return -ENOMEM;
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padata_replace(pinst, pd);
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}
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return 0;
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}
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/*
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* padata_add_cpu - add a cpu to the padata cpumask
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*
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* @pinst: padata instance
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* @cpu: cpu to add
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*/
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int padata_add_cpu(struct padata_instance *pinst, int cpu)
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{
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int err;
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mutex_lock(&pinst->lock);
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get_online_cpus();
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cpumask_set_cpu(cpu, pinst->cpumask);
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err = __padata_add_cpu(pinst, cpu);
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put_online_cpus();
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mutex_unlock(&pinst->lock);
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return err;
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}
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EXPORT_SYMBOL(padata_add_cpu);
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static int __padata_remove_cpu(struct padata_instance *pinst, int cpu)
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{
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struct parallel_data *pd;
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if (cpumask_test_cpu(cpu, cpu_online_mask)) {
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pd = padata_alloc_pd(pinst, pinst->cpumask);
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if (!pd)
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return -ENOMEM;
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padata_replace(pinst, pd);
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}
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return 0;
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}
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/*
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* padata_remove_cpu - remove a cpu from the padata cpumask
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*
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* @pinst: padata instance
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* @cpu: cpu to remove
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*/
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int padata_remove_cpu(struct padata_instance *pinst, int cpu)
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{
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int err;
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mutex_lock(&pinst->lock);
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get_online_cpus();
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cpumask_clear_cpu(cpu, pinst->cpumask);
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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 NOTIFY_BAD;
|
|
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 NOTIFY_BAD;
|
|
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();
|
|
|
|
while (atomic_read(&pinst->pd->refcnt) != 0)
|
|
yield();
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
unregister_hotcpu_notifier(&pinst->cpu_notifier);
|
|
#endif
|
|
padata_free_pd(pinst->pd);
|
|
free_cpumask_var(pinst->cpumask);
|
|
kfree(pinst);
|
|
}
|
|
EXPORT_SYMBOL(padata_free);
|