4 * This file is part of BeRTOS.
6 * Bertos is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
20 * As a special exception, you may use this file as part of a free software
21 * library without restriction. Specifically, if other files instantiate
22 * templates or use macros or inline functions from this file, or you compile
23 * this file and link it with other files to produce an executable, this
24 * file does not by itself cause the resulting executable to be covered by
25 * the GNU General Public License. This exception does not however
26 * invalidate any other reasons why the executable file might be covered by
27 * the GNU General Public License.
29 * Copyright 2008 Bernie Innocenti <bernie@codewiz.org>
32 * \brief Idle loop for preemptive scheduling
35 * \author Bernie Innocenti <bernie@codewiz.org>
41 #include <cpu/power.h> // cpu_relax()
42 #include <cfg/module.h>
43 #include <cpu/types.h> // INT_MIN
45 #include <kern/proc_p.h>
47 struct Process *idle_proc;
49 static PROC_DEFINE_STACK(idle_stack, KERN_MINSTACKSIZE);
54 * This process never dies and never sleeps. It's also quite lazy, apathic
55 * and sometimes even a little antisocial.
57 * Having an idle process costs us some stack space, but simplifies the
58 * interrupt-driven preemption logic because there is always a user
59 * context to which we can return.
61 * The idle process is not required for cooperative task switching.
63 static NORETURN void idle(void)
75 * Idle will be added to the ProcReadyList, but immediately removed
76 * after the first cpu_relax() execution.
78 * XXX: it would be better to never add idle_proc to the ProcReadyList,
79 * e.g., changing the prototype of proc_new() (or introducing a
80 * proc_new_nostart()) to allow the creation of "sleeping" tasks.
82 idle_proc = proc_new(idle, NULL, sizeof(idle_stack), idle_stack);
83 proc_setPri(idle_proc, INT_MIN);