linux/kernel/padata.c
Steffen Klassert ee83655512 padata: Block until the instance is unused on stop
This patch makes padata_stop to block until the padata
instance is unused. Also we split padata_stop to a locked
and a unlocked version. This is in preparation to be able
to change the cpumask after a call to patata stop.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2010-07-14 20:29:29 +08:00

797 lines
17 KiB
C

/*
* 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);
}
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 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
*/
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_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)
{
#ifdef CONFIG_HOTPLUG_CPU
unregister_hotcpu_notifier(&pinst->cpu_notifier);
#endif
padata_stop(pinst);
padata_free_pd(pinst->pd);
free_cpumask_var(pinst->cpumask);
kfree(pinst);
}
EXPORT_SYMBOL(padata_free);