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kernel: use lockless list for smp_call_function_single 

Make smp_call_function_single and friends more efficient by using a
lockless list.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Christoph Hellwig 2014-01-30 15:45:47 -08:00 committed by Linus Torvalds
parent 0c692d0784
commit 6897fc22ea
3 changed files with 19 additions and 43 deletions
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5
include/linux/blkdev.h
View File

@ -95,10 +95,7 @@ enum rq_cmd_type_bits {
* as well!
*/
struct request {
union {
struct list_head queuelist;
struct llist_node ll_list;
};
struct list_head queuelist;
union {
struct call_single_data csd;
struct work_struct mq_flush_data;

6
include/linux/smp.h
View File

@ -11,12 +11,16 @@
#include <linux/list.h>
#include <linux/cpumask.h>
#include <linux/init.h>
#include <linux/llist.h>
extern void cpu_idle(void);
typedef void (*smp_call_func_t)(void *info);
struct call_single_data {
struct list_head list;
union {
struct list_head list;
struct llist_node llist;
};
smp_call_func_t func;
void *info;
u16 flags;

51
kernel/smp.c
View File

@ -28,12 +28,7 @@ struct call_function_data {
static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
struct call_single_queue {
struct list_head list;
raw_spinlock_t lock;
};
static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue);
static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
static int
hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
@ -85,12 +80,8 @@ void __init call_function_init(void)
void *cpu = (void *)(long)smp_processor_id();
int i;
for_each_possible_cpu(i) {
struct call_single_queue *q = &per_cpu(call_single_queue, i);
raw_spin_lock_init(&q->lock);
INIT_LIST_HEAD(&q->list);
}
for_each_possible_cpu(i)
init_llist_head(&per_cpu(call_single_queue, i));
hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
register_cpu_notifier(&hotplug_cfd_notifier);
@ -141,18 +132,9 @@ static void csd_unlock(struct call_single_data *csd)
*/
static void generic_exec_single(int cpu, struct call_single_data *csd, int wait)
{
struct call_single_queue *dst = &per_cpu(call_single_queue, cpu);
unsigned long flags;
int ipi;
if (wait)
csd->flags |= CSD_FLAG_WAIT;
raw_spin_lock_irqsave(&dst->lock, flags);
ipi = list_empty(&dst->list);
list_add_tail(&csd->list, &dst->list);
raw_spin_unlock_irqrestore(&dst->lock, flags);
/*
* The list addition should be visible before sending the IPI
* handler locks the list to pull the entry off it because of
@ -164,7 +146,7 @@ static void generic_exec_single(int cpu, struct call_single_data *csd, int wait)
* locking and barrier primitives. Generic code isn't really
* equipped to do the right thing...
*/
if (ipi)
if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
arch_send_call_function_single_ipi(cpu);
if (wait)
@ -177,27 +159,26 @@ static void generic_exec_single(int cpu, struct call_single_data *csd, int wait)
*/
void generic_smp_call_function_single_interrupt(void)
{
struct call_single_queue *q = &__get_cpu_var(call_single_queue);
LIST_HEAD(list);
struct llist_node *entry, *next;
/*
* Shouldn't receive this interrupt on a cpu that is not yet online.
*/
WARN_ON_ONCE(!cpu_online(smp_processor_id()));
raw_spin_lock(&q->lock);
list_replace_init(&q->list, &list);
raw_spin_unlock(&q->lock);
entry = llist_del_all(&__get_cpu_var(call_single_queue));
entry = llist_reverse_order(entry);
while (!list_empty(&list)) {
while (entry) {
struct call_single_data *csd;
csd = list_entry(list.next, struct call_single_data, list);
list_del(&csd->list);
next = entry->next;
csd = llist_entry(entry, struct call_single_data, llist);
csd->func(csd->info);
csd_unlock(csd);
entry = next;
}
}
@ -411,17 +392,11 @@ void smp_call_function_many(const struct cpumask *mask,
for_each_cpu(cpu, cfd->cpumask) {
struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);
struct call_single_queue *dst =
&per_cpu(call_single_queue, cpu);
unsigned long flags;
csd_lock(csd);
csd->func = func;
csd->info = info;
raw_spin_lock_irqsave(&dst->lock, flags);
list_add_tail(&csd->list, &dst->list);
raw_spin_unlock_irqrestore(&dst->lock, flags);
llist_add(&csd->llist, &per_cpu(call_single_queue, cpu));
}
/* Send a message to all CPUs in the map */