diff --git a/kernel/proc.c b/kernel/proc.c
index 4354ec5..130d9ce 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -473,6 +473,7 @@ scheduler(void)
       release(&p->lock);
     }
     if(found == 0) {
+      // nothing to run; stop running on this core until an interrupt.
       intr_on();
       asm volatile("wfi");
     }