provide a way to init percpu_counters that are supposed to be used from irq
safe contexts.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 include/linux/percpu_counter.h |    4 ++++
 lib/percpu_counter.c           |    8 ++++++++
 2 files changed, 12 insertions(+)

Index: linux-2.6/include/linux/percpu_counter.h
===================================================================
--- linux-2.6.orig/include/linux/percpu_counter.h
+++ linux-2.6/include/linux/percpu_counter.h
@@ -31,6 +31,8 @@ struct percpu_counter {
 #endif
 
 void percpu_counter_init(struct percpu_counter *fbc, s64 amount);
+void percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount);
+
 void percpu_counter_destroy(struct percpu_counter *fbc);
 void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
 void __percpu_counter_mod(struct percpu_counter *fbc, s32 amount, s32 batch);
@@ -89,6 +91,8 @@ static inline void percpu_counter_init(s
 	fbc->count = amount;
 }
 
+#define percpu_counter_init_irq percpu_counter_init
+
 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
 {
 }
Index: linux-2.6/lib/percpu_counter.c
===================================================================
--- linux-2.6.orig/lib/percpu_counter.c
+++ linux-2.6/lib/percpu_counter.c
@@ -87,6 +87,8 @@ s64 __percpu_counter_sum(struct percpu_c
 }
 EXPORT_SYMBOL(__percpu_counter_sum);
 
+static struct lock_class_key percpu_counter_irqsafe;
+
 void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
 {
 	spin_lock_init(&fbc->lock);
@@ -100,6 +102,12 @@ void percpu_counter_init(struct percpu_c
 }
 EXPORT_SYMBOL(percpu_counter_init);
 
+void percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount)
+{
+	percpu_counter_init(fbc, amount);
+	lockdep_set_class(&fbc->lock, &percpu_counter_irqsafe);
+}
+
 void percpu_counter_destroy(struct percpu_counter *fbc)
 {
 	free_percpu(fbc->counters);

--