/* * 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