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/*
* Fast batching percpu counters.
*/
#include <linux/percpu_counter.h>
#include <linux/notifier.h>
#include <linux/mutex.h>
#include <linux/init.h>
#include <linux/cpu.h>
#include <linux/module.h>
#ifdef CONFIG_HOTPLUG_CPU
static LIST_HEAD(percpu_counters);
static DEFINE_MUTEX(percpu_counters_lock);
#endif
void percpu_counter_mod(struct percpu_counter *fbc, s32 amount)
{
long count;
s32 *pcount;
int cpu = get_cpu();
pcount = per_cpu_ptr(fbc->counters, cpu);
count = *pcount + amount;
if (count >= FBC_BATCH || count <= -FBC_BATCH) {
spin_lock(&fbc->lock);
fbc->count += count;
*pcount = 0;
spin_unlock(&fbc->lock);
} else {
*pcount = count;
}
put_cpu();
}
EXPORT_SYMBOL(percpu_counter_mod);
/*
* Add up all the per-cpu counts, return the result. This is a more accurate
* but much slower version of percpu_counter_read_positive()
*/
s64 percpu_counter_sum(struct percpu_counter *fbc)
{
s64 ret;
int cpu;
spin_lock(&fbc->lock);
ret = fbc->count;
for_each_online_cpu(cpu) {
s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
ret += *pcount;
}
spin_unlock(&fbc->lock);
return ret < 0 ? 0 : ret;
}
EXPORT_SYMBOL(percpu_counter_sum);
void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
{
spin_lock_init(&fbc->lock);
fbc->count = amount;
fbc->counters = alloc_percpu(s32);
#ifdef CONFIG_HOTPLUG_CPU
mutex_lock(&percpu_counters_lock);
list_add(&fbc->list, &percpu_counters);
mutex_unlock(&percpu_counters_lock);
#endif
}
EXPORT_SYMBOL(percpu_counter_init);
void percpu_counter_destroy(struct percpu_counter *fbc)
{
free_percpu(fbc->counters);
#ifdef CONFIG_HOTPLUG_CPU
mutex_lock(&percpu_counters_lock);
list_del(&fbc->list);
mutex_unlock(&percpu_counters_lock);
#endif
}
EXPORT_SYMBOL(percpu_counter_destroy);
#ifdef CONFIG_HOTPLUG_CPU
static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
unsigned long action, void *hcpu)
{
unsigned int cpu;
struct percpu_counter *fbc;
if (action != CPU_DEAD)
return NOTIFY_OK;
cpu = (unsigned long)hcpu;
mutex_lock(&percpu_counters_lock);
list_for_each_entry(fbc, &percpu_counters, list) {
s32 *pcount;
spin_lock(&fbc->lock);
pcount = per_cpu_ptr(fbc->counters, cpu);
fbc->count += *pcount;
*pcount = 0;
spin_unlock(&fbc->lock);
}
mutex_unlock(&percpu_counters_lock);
return NOTIFY_OK;
}
static int __init percpu_counter_startup(void)
{
hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
return 0;
}
module_init(percpu_counter_startup);
#endif
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