Handout

kernel/thread/scheduler.cc

@@ -0,0 +1,61 @@
+// vim: set noet ts=4 sw=4:
+
+#include "scheduler.h"
+
+#include "../arch/core.h"
+#include "../debug/assert.h"  // IWYU pragma: keep
+
+Scheduler::Scheduler() {}
+
+Thread *Scheduler::getNext() {
+	Thread *next = readylist.dequeue();
+	if (next == nullptr) {
+		next = &idleThread;
+	}
+
+	assert(next != nullptr && "No thread available!");
+	return next;
+}
+
+void Scheduler::schedule() { dispatcher.go(getNext()); }
+
+void Scheduler::ready(Thread *that) {
+	assert(that != nullptr && "nullptr pointer not allowed for ready list!");
+
+	assert(static_cast<Thread *>(&idleThread) != that &&
+		   "IdleThread must not be placed in ready list!");
+
+	readylist.enqueue(*that);
+}
+
+void Scheduler::resume(bool ready) {
+	Thread *me = dispatcher.active();
+	assert(me != nullptr && "Pointer to active thread should never be nullptr");
+
+	if (true) {
+		// Be careful, never put the idle thread into the ready list
+		bool is_idle_thread = static_cast<Thread *>(&idleThread) == me;
+
+		if (ready && readylist.is_empty()) {
+			return;
+		} else if (!is_idle_thread) {
+			if (ready) readylist.enqueue(*me);
+		}
+	}
+
+	dispatcher.dispatch(getNext());
+}
+
+void Scheduler::exit() {
+	Thread *next = getNext();
+
+	dispatcher.dispatch(next);
+}
+
+void Scheduler::kill(Thread *that) {
+	if (dispatcher.active() == that) {
+		exit();
+	}
+}
+
+bool Scheduler::isEmpty() const { return readylist.is_empty(); }