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>
diff --git a/kernel/smp.c b/kernel/smp.c
index bd9f940..4ad913e 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -28,12 +28,7 @@
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 *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 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 @@
* 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 @@
*/
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 @@
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 */