iris/schedule.ccp

#pypp 0
// Iris: micro-kernel for a capability-based operating system.
// schedule.ccp: Thread scheduling.
// Copyright 2009 Bas Wijnen <wijnen@debian.org>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

#include "kernel.hh"

static void run_thread (kThread *thread):
	thread->schedule_next = first_scheduled
	if thread->schedule_next:
		thread->schedule_next->schedule_prev = thread
	thread->schedule_prev = NULL
	first_scheduled = thread

static void unrun_thread (kThread *thread):
	if current == thread:
		current = thread->schedule_next
	if thread->schedule_prev:
		thread->schedule_prev->schedule_next = thread->schedule_next
	else:
		first_scheduled = thread->schedule_next
	if thread->schedule_next:
		thread->schedule_next->schedule_prev = thread->schedule_prev

void kThread::run ():
	if flags & Kernel::Thread::RUNNING:
		return
	flags |= Kernel::Thread::RUNNING
	if is_waiting ():
		return
	run_thread (this)

void kThread::unrun ():
	if !(flags & Kernel::Thread::RUNNING):
		return
	flags &= ~Kernel::Thread::RUNNING
	if is_waiting ():
		return
	unrun_thread (this)

void kThread::unwait ():
	flags &= ~Kernel::Thread::WAITING
	if flags & Kernel::Thread::RUNNING:
		run_thread (this)

static void alarm_tick (kReceiver *recv):
	if !recv->alarm_count:
		// Send message and stop counting.
		kCapability::Context c
		for unsigned i = 0; i < 2; ++i:
			c.data[i] = 0
		recv->send_message (~0, &c)
		if recv->prev_alarm:
			recv->prev_alarm->next_alarm = recv->next_alarm
		else:
			first_alarm = recv->next_alarm
		if recv->next_alarm:
			recv->next_alarm->prev_alarm = recv->prev_alarm
		// Fall through to let alarm_count be ~0.  This is required, because it is the indicator for no running alarm.
	--recv->alarm_count

void kThread::wait ():
	if flags & Kernel::Thread::RUNNING:
		unrun_thread (this)
	flags |= Kernel::Thread::WAITING
	// Try to receive a message from a kReceiver immediately.
	for kReceiver *r = receivers; r; r = r->next_owned:
		if r->try_deliver ():
			return

void schedule ():
	if current:
		current = current->schedule_next
	if !current:
		current = first_scheduled

void timer_interrupt ():
	kReceiver *recv, *next
	for recv = first_alarm; recv; recv = next:
		next = (kReceiver *)recv->next
		alarm_tick (recv)
	//schedule ()