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 preemptive multitasking scheduler.
34 * All voluntary and preemptive context switching happens on exit from
35 * a common interrupt (signal) dispatcher. Preemption on quantum timeout
36 * is regulated by a soft-timer. Other kinds of preemption could happen
37 * if an interrupt sends a signal to a higher priority process (but this
38 * is still unimplemented).
40 * In the POSIX implementaiton, context switching is done by the portable
41 * SVR4 swapcontext() facility.
43 * \version $Id: proc.c 1616 2008-08-10 19:41:26Z bernie $
44 * \author Bernie Innocenti <bernie@codewiz.org>
47 #include <cfg/cfg_kern.h>
49 #if CONFIG_KERN_PREEMPT
56 #include <kern/monitor.h>
57 #include <cpu/frame.h> // CPU_IDLE
58 #include <cpu/irq.h> // IRQ_DISABLE()...
59 #include <drv/timer.h>
60 #include <cfg/module.h>
61 #include <cfg/depend.h> // CONFIG_DEPEND()
63 // Check config dependencies
64 CONFIG_DEPEND(CONFIG_KERN_PREEMPT, CONFIG_KERN_SCHED && CONFIG_TIMER_EVENTS && CONFIG_KERN_IRQ);
68 int preempt_forbid_cnt;
70 static Timer preempt_timer;
73 void proc_schedule(void)
77 ASSERT(preempt_forbid_cnt == 0);
78 LIST_ASSERT_VALID(&ProcReadyList);
79 CurrentProcess = (struct Process *)list_remHead(&ProcReadyList);
80 ASSERT2(CurrentProcess, "no idle proc?");
84 TRACEMSG("launching %p:%s", CurrentProcess, proc_currentName());
87 void proc_preempt(UNUSED_ARG(void *, param))
89 if (!preempt_forbid_cnt)
94 Process *rival = (Process *)LIST_HEAD(&ProcReadyList);
95 if (rival && rival->link.pri >= CurrentProcess->link.pri)
99 TRACEMSG("preempting %p:%s", CurrentProcess, proc_currentName());
101 // FIXME: this still breaks havoc, probably because of some reentrancy issue
103 SCHED_ENQUEUE(CurrentProcess);
113 timer_setDelay(&preempt_timer, CONFIG_KERN_QUANTUM);
114 timer_add(&preempt_timer);
117 void proc_switch(void)
119 ATOMIC(LIST_ASSERT_VALID(&ProcReadyList));
120 TRACEMSG("%p:%s", CurrentProcess, proc_currentName());
121 ATOMIC(LIST_ASSERT_VALID(&ProcReadyList));
123 /* Sleeping with IRQs disabled or preemption forbidden is illegal */
124 IRQ_ASSERT_ENABLED();
125 ASSERT(preempt_forbid_cnt == 0);
127 // Will invoke proc_switch() in interrupt context
131 void proc_yield(void)
133 TRACEMSG("%p:%s", CurrentProcess, proc_currentName());
136 SCHED_ENQUEUE(CurrentProcess);
142 void proc_entry(void (*user_entry)(void))
148 void preempt_init(void)
153 irq_register(SIGUSR1, proc_schedule);
155 timer_setSoftint(&preempt_timer, proc_preempt, NULL);
156 timer_setDelay(&preempt_timer, CONFIG_KERN_QUANTUM);
157 timer_add(&preempt_timer);
164 #endif // CONFIG_KERN_PREEMPT