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 Simple realtime multitasking scheduler.
33 * Context switching is only done cooperatively.
35 * \version $Id: proc.c 1616 2008-08-10 19:41:26Z bernie $
36 * \author Bernie Innocenti <bernie@codewiz.org>
43 #include <cpu/frame.h> // CPU_IDLE
44 #include <drv/timer.h>
45 #include <cfg/module.h>
49 * The time sharing scheduler forces a task switch when the current
50 * process has exhausted its quantum.
57 * Disable preemptive task switching.
59 * The scheduler maintains a per-process nesting counter. Task switching is
60 * effectively re-enabled only when the number of calls to proc_permit()
61 * matches the number of calls to proc_forbid().
63 * Calling functions that could sleep while task switching is disabled
64 * is dangerous, although supported. Preemptive task switching is
65 * resumed while the process is sleeping and disabled again as soon as
70 void proc_forbid(void)
72 /* No need to protect against interrupts here. */
73 ++CurrentProcess->forbid_cnt;
77 * Re-enable preemptive task switching.
81 void proc_permit(void)
83 /* No need to protect against interrupts here. */
84 --CurrentProcess->forbid_cnt;
88 void proc_preempt(void)
92 ATOMIC(LIST_ASSERT_VALID(&ProcReadyList));
96 /* Poll on the ready queue for the first ready process */
97 while (!(CurrentProcess = (struct Process *)list_remHead(&ProcReadyList)))
101 * Make sure we physically reenable interrupts here, no matter what
102 * the current task status is. This is important because if we
103 * are idle-spinning, we must allow interrupts, otherwise no
104 * process will ever wake up.
106 * During idle-spinning, an interrupt can occur and it may
107 * modify \p ProcReadyList. To ensure that compiler reload this
108 * variable every while cycle we call CPU_MEMORY_BARRIER.
109 * The memory barrier ensure that all variables used in this context
113 //FIXME: calls Qt stuff from sighandler! CPU_IDLE;
116 //TRACEMSG("hello3");
122 void proc_preempt_timer(UNUSED_ARG(void *, param))
127 TRACEMSG("preempting %p:%s", CurrentProcess, CurrentProcess->monitor.name);
128 SCHED_ENQUEUE(CurrentProcess);
134 timer_setDelay(&preempt_timer, CONFIG_KERN_QUANTUM);
135 timer_add(&preempt_timer);
138 void proc_schedule(void)
142 // Will invoke proc_preempt() in interrupt context
146 void proc_yield(void)
148 ATOMIC(SCHED_ENQUEUE(CurrentProcess));
153 void proc_entry(void (*user_entry)(void))
159 void preempt_init(void)
164 irq_register(SIGUSR1, proc_preempt);
166 timer_setSoftint(&preempt_timer, proc_preempt_timer, NULL);
167 timer_setDelay(&preempt_timer, CONFIG_KERN_QUANTUM);
168 timer_add(&preempt_timer);