1 files changed, 146 insertions, 0 deletions

diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
new file mode 100644
index 0000000..b255b93
--- /dev/null
+++ b/lib/percpu_counter.c
@@ -0,0 +1,146 @@
+/*
+ * 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_set(struct percpu_counter *fbc, s64 amount)
+{
+	int cpu;
+
+	spin_lock(&fbc->lock);
+	for_each_possible_cpu(cpu) {
+		s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
+		*pcount = 0;
+	}
+	fbc->count = amount;
+	spin_unlock(&fbc->lock);
+}
+EXPORT_SYMBOL(percpu_counter_set);
+
+void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
+{
+	s64 count;
+	s32 *pcount;
+	int cpu = get_cpu();
+
+	pcount = per_cpu_ptr(fbc->counters, cpu);
+	count = *pcount + amount;
+	if (count >= batch || count <= -batch) {
+		spin_lock(&fbc->lock);
+		fbc->count += count;
+		*pcount = 0;
+		spin_unlock(&fbc->lock);
+	} else {
+		*pcount = count;
+	}
+	put_cpu();
+}
+EXPORT_SYMBOL(__percpu_counter_add);
+
+/*
+ * 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;
+}
+EXPORT_SYMBOL(__percpu_counter_sum);
+
+static struct lock_class_key percpu_counter_irqsafe;
+
+int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
+{
+	spin_lock_init(&fbc->lock);
+	fbc->count = amount;
+	fbc->counters = alloc_percpu(s32);
+	if (!fbc->counters)
+		return -ENOMEM;
+#ifdef CONFIG_HOTPLUG_CPU
+	mutex_lock(&percpu_counters_lock);
+	list_add(&fbc->list, &percpu_counters);
+	mutex_unlock(&percpu_counters_lock);
+#endif
+	return 0;
+}
+EXPORT_SYMBOL(percpu_counter_init);
+
+int percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount)
+{
+	int err;
+
+	err = percpu_counter_init(fbc, amount);
+	if (!err)
+		lockdep_set_class(&fbc->lock, &percpu_counter_irqsafe);
+	return err;
+}
+
+void percpu_counter_destroy(struct percpu_counter *fbc)
+{
+	if (!fbc->counters)
+		return;
+
+#ifdef CONFIG_HOTPLUG_CPU
+	mutex_lock(&percpu_counters_lock);
+	list_del(&fbc->list);
+	mutex_unlock(&percpu_counters_lock);
+#endif
+	free_percpu(fbc->counters);
+	fbc->counters = NULL;
+}
+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;
+		unsigned long flags;
+
+		spin_lock_irqsave(&fbc->lock, flags);
+		pcount = per_cpu_ptr(fbc->counters, cpu);
+		fbc->count += *pcount;
+		*pcount = 0;
+		spin_unlock_irqrestore(&fbc->lock, flags);
+	}
+	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