Index: kernel/generic/src/interrupt/interrupt.c
===================================================================
--- kernel/generic/src/interrupt/interrupt.c	(revision b584cd4cef50e6fa6eff42a312e9c90f0f7eb213)
+++ kernel/generic/src/interrupt/interrupt.c	(revision 402eda58922a8ad7839ce8ebb06d82d8f0e6710a)
@@ -99,4 +99,6 @@
 void exc_dispatch(unsigned int n, istate_t *istate)
 {
+	ASSERT(CPU);
+	
 #if (IVT_ITEMS > 0)
 	ASSERT(n < IVT_ITEMS);
@@ -109,4 +111,14 @@
 		irq_spinlock_unlock(&THREAD->lock, false);
 	}
+	
+	/* Account CPU usage if it has waked up from sleep */
+	irq_spinlock_lock(&CPU->lock, false);
+	if (CPU->idle) {
+		uint64_t now = get_cycle();
+		CPU->idle_cycles += now - CPU->last_cycle;
+		CPU->last_cycle = now;
+		CPU->idle = false;
+	}
+	irq_spinlock_unlock(&CPU->lock, false);
 	
 	uint64_t begin_cycle = get_cycle();