Handout

kernel/thread/idlethread.cc

@@ -0,0 +1,31 @@
+#include "idlethread.h"
+
+#include "../arch/core.h"
+#include "../arch/lapic.h"
+#include "../debug/output.h"
+#include "../interrupt/guard.h"
+#include "../thread/scheduler.h"
+
+void IdleThread::action() {
+	while (true) {
+		Core::Interrupt::disable();
+		if (Guard::unsafeConstAccess()
+				.scheduler.isEmpty()) {	 // XXX: not a fan ...
+			// To save energy we can disable the timer on a core as soon as no
+			// clock needs to be managed. This function is called from the idle
+			// loop.
+			bool can_sleep =
+				!Guard::unsafeConstAccess().bellringer.bellPending();
+			if (can_sleep) {
+				LAPIC::Timer::setMasked(true);
+			}
+			Core::idle();
+			// We woke up. Start ticking again
+			LAPIC::Timer::setMasked(false);
+		} else {
+			Core::Interrupt::enable();
+			Guarded g = Guard::enter();
+			g.vault().scheduler.resume();
+		}
+	}
+}