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 (Thread *thread):
	thread->schedule_next = first_scheduled
	if thread->schedule_next:
		thread->schedule_next->schedule_prev = thread
	first_scheduled = thread

static void unrun_thread (Thread *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 Thread::sleep ():
	schedule_next = first_sleeper
	if schedule_next:
		schedule_next->schedule_prev = this
	schedule_prev = NULL
	first_sleeper = this

void Thread::unsleep ():
	if schedule_next:
		schedule_next->schedule_prev = schedule_prev
	if schedule_prev:
		schedule_prev->schedule_next = schedule_next
	else:
		first_sleeper = schedule_next

void Thread::run ():
	if flags & THREAD_FLAG_RUNNING:
		return
	flags |= THREAD_FLAG_RUNNING
	if flags & THREAD_FLAG_WAITING:
		if sleep_count != ~0:
			sleep ()
		return
	run_thread (this)

void Thread::unrun ():
	if !(flags & THREAD_FLAG_RUNNING):
		return
	flags &= ~THREAD_FLAG_RUNNING
	if flags & THREAD_FLAG_WAITING:
		if sleep_count != ~0:
			unsleep ()
		return
	unrun_thread (this)

void Thread::unwait ():
	if !(flags & THREAD_FLAG_WAITING):
		return
	flags &= ~THREAD_FLAG_WAITING
	if sleep_count != ~0:
		unsleep ()
	if flags & THREAD_FLAG_RUNNING:
		run_thread (this)

static void sleep_tick (Thread *thread):
	if !thread->sleep_count:
		thread->unwait ()
		// Time-out: let the thread know with a special message.
		Capability::Context c
		for unsigned i = 0; i < 4; ++i:
			c.data[i] = 0
			c.cap[i] = NULL
			c.copy[i] = false
		Thread_arch_receive (thread, ~0, &c)
		// Fall through to let sleep be set to ~0, so the next wait will be infinitely long again.
	--thread->sleep_count

void Thread::wait ():
	if flags & THREAD_FLAG_WAITING:
		return
	if flags & THREAD_FLAG_RUNNING:
		unrun_thread (this)
	flags |= THREAD_FLAG_WAITING
	if sleep_count != ~0:
		sleep ()
	// Try to receive a message from a Receiver immediately.
	for Receiver *r = receivers; r; r = r->next_owned:
		if r->try_deliver ():
			return
	if sleep_count != ~0:
		sleep_tick (this)

void schedule ():
	Thread *old = current
	if current:
		current = current->schedule_next
	if !current:
		current = first_scheduled
		if !current:
			current = &idle

void timer_interrupt ():
	//panic (0x88877744, "Timer interrupt")
	Thread *thread, *next
	for thread = first_sleeper; thread; thread = next:
		next = thread->next
		sleep_tick (thread)
	schedule ()
	//#ifndef NDEBUG
	//static bool ledstate = false
	//dbg_led (false, false, ledstate = !ledstate)
	//#endif