Merge tag 'sound-4.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai...

[mirror_ubuntu-artful-kernel.git] / lib / percpu_counter.c

diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
index 8ee7e5ec21be23f658323a9cea840e3d7fb41ce6..3bf4a9984f4cb094b7d74550be1897c20ac292a6 100644 (file)
--- a/lib/percpu_counter.c
+++ b/lib/percpu_counter.c
@@ -72,6 +72,13 @@ void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
 }
 EXPORT_SYMBOL(percpu_counter_set);
 
+/**
+ * This function is both preempt and irq safe. The former is due to explicit
+ * preemption disable. The latter is guaranteed by the fact that the slow path
+ * is explicitly protected by an irq-safe spinlock whereas the fast patch uses
+ * this_cpu_add which is irq-safe by definition. Hence there is no need muck
+ * with irq state before calling this one
+ */
 void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch)
 {
        s64 count;