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 2001,2004 Develer S.r.l. (http://www.develer.com/)
30 * Copyright 1999,2000,2001 Bernardo Innocenti <bernie@develer.com>
34 * \brief Simple realtime multitasking scheduler.
35 * Context switching is only done cooperatively.
39 * \author Bernardo Innocenti <bernie@develer.com>
40 * \author Stefano Fedrigo <aleph@develer.com>
45 *#* Revision 1.32 2006/09/20 14:19:23 marco
48 *#* Revision 1.31 2006/07/19 12:56:27 bernie
49 *#* Convert to new Doxygen style.
51 *#* Revision 1.30 2006/03/27 04:49:23 bernie
52 *#* CPU_IDLE(): Fix for new emulator.
54 *#* Revision 1.29 2006/02/24 01:17:05 bernie
55 *#* Update for new emulator.
57 *#* Revision 1.28 2006/02/21 16:06:55 bernie
58 *#* Cleanup/update process scheduling.
60 *#* Revision 1.27 2005/11/04 16:20:02 bernie
61 *#* Fix reference to README.devlib in header.
63 *#* Revision 1.26 2005/04/11 19:10:28 bernie
64 *#* Include top-level headers from cfg/ subdir.
66 *#* Revision 1.25 2005/03/15 00:20:54 bernie
67 *#* proc_schedule(): New sanity check.
69 *#* Revision 1.24 2005/01/08 09:20:54 bernie
70 *#* Remove unused variable.
72 *#* Revision 1.23 2004/12/13 12:07:06 bernie
73 *#* DISABLE_IRQSAVE/ENABLE_IRQRESTORE: Convert to IRQ_SAVE_DISABLE/IRQ_RESTORE.
75 *#* Revision 1.22 2004/12/13 11:51:08 bernie
76 *#* DISABLE_INTS/ENABLE_INTS: Convert to IRQ_DISABLE/IRQ_ENABLE.
78 *#* Revision 1.21 2004/11/28 23:20:25 bernie
79 *#* Remove obsolete INITLIST macro.
81 *#* Revision 1.20 2004/11/16 22:37:14 bernie
82 *#* Replace IPTR with iptr_t.
84 *#* Revision 1.19 2004/10/19 11:47:39 bernie
85 *#* Kill warnings when !CONFIG_PROC_MONITOR.
87 *#* Revision 1.18 2004/10/19 08:54:43 bernie
88 *#* Initialize forbid_cnt; Formatting/comments fixes.
90 *#* Revision 1.17 2004/10/19 08:47:13 bernie
91 *#* proc_rename(), proc_forbid(), proc_permit(): New functions.
93 *#* Revision 1.16 2004/10/03 20:39:28 bernie
94 *#* Import changes from sc/firmware.
96 *#* Revision 1.15 2004/09/20 03:29:39 bernie
99 *#* Revision 1.14 2004/09/14 21:06:44 bernie
100 *#* Use debug.h instead of kdebug.h.
102 *#* Revision 1.13 2004/08/29 21:58:53 bernie
103 *#* Include macros.h explicityl.
105 *#* Revision 1.11 2004/08/24 16:09:08 bernie
106 *#* Add missing header.
108 *#* Revision 1.10 2004/08/24 16:07:01 bernie
109 *#* Use kputs()/kputchar() when possible.
111 *#* Revision 1.9 2004/08/24 14:26:57 bernie
112 *#* monitor_debug_stacks(): Conditionally compile on CONFIG_KERN_MONITOR.
114 *#* Revision 1.8 2004/08/14 19:37:57 rasky
115 *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
117 *#* Revision 1.7 2004/08/02 20:20:29 aleph
118 *#* Merge from project_ks
120 *#* Revision 1.6 2004/07/30 14:24:16 rasky
121 *#* Task switching con salvataggio perfetto stato di interrupt (SR)
122 *#* Kernel monitor per dump informazioni su stack dei processi
124 *#* Revision 1.5 2004/07/14 14:18:09 rasky
125 *#* Merge da SC: Rimosso timer dentro il task, che รจ uno spreco di memoria per troppi task
127 *#* Revision 1.4 2004/07/13 19:21:28 aleph
128 *#* Avoid warning for unused arg when compiled without some CONFIG_KERN_xx options
130 *#* Revision 1.3 2004/06/06 18:37:57 bernie
131 *#* Rename event macros to look like regular functions.
133 *#* Revision 1.2 2004/06/03 11:27:09 bernie
134 *#* Add dual-license information.
136 *#* Revision 1.1 2004/05/23 17:27:00 bernie
137 *#* Import kern/ subdirectory.
144 #include <mware/event.h>
146 #include <cfg/debug.h>
147 #include <cfg/arch_config.h> /* ARCH_EMUL */
148 #include <cfg/macros.h> /* ABS() */
150 #include <string.h> /* memset() */
153 * CPU dependent context switching routines.
155 * \note This function *MUST* preserve also the status of the interrupts.
157 EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
158 EXTERN_C int asm_switch_version(void);
161 * The scheduer tracks ready and waiting processes
162 * by enqueuing them in these lists. A pointer to the currently
163 * running process is stored in the CurrentProcess pointer.
165 * NOTE: these variables are protected by DI/EI locking
167 REGISTER Process *CurrentProcess;
168 REGISTER List ProcReadyList;
171 #if CONFIG_KERN_PREEMPTIVE
173 * The time sharing scheduler forces a task switch when
174 * the current process has consumed its quantum.
180 /* In Win32 we must emulate stack on the real process stack */
181 #if (ARCH & ARCH_EMUL)
182 extern List StackFreeList;
185 /** The main process (the one that executes main()). */
186 struct Process MainProcess;
189 static void proc_init_struct(Process *proc)
191 /* Avoid warning for unused argument. */
194 #if CONFIG_KERN_SIGNALS
198 #if CONFIG_KERN_PREEMPTIVE
199 proc->forbid_cnt = 0;
210 LIST_INIT(&ProcReadyList);
212 #if CONFIG_KERN_MONITOR
216 /* We "promote" the current context into a real process. The only thing we have
217 * to do is create a PCB and make it current. We don't need to setup the stack
218 * pointer because it will be written the first time we switch to another process.
220 proc_init_struct(&MainProcess);
221 CurrentProcess = &MainProcess;
223 /* Make sure the assembly routine is up-to-date with us */
224 ASSERT(asm_switch_version() == 1);
229 * Create a new process, starting at the provided entry point.
231 * \return Process structure of new created process
232 * if successful, NULL otherwise.
234 struct Process *proc_new_with_name(UNUSED(const char *, name), void (*entry)(void), iptr_t data, size_t stacksize, cpustack_t *stack_base)
238 size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
240 bool free_stack = false;
243 #if (ARCH & ARCH_EMUL)
244 /* Ignore stack provided by caller and use the large enough default instead. */
245 stack_base = (cpustack_t *)LIST_HEAD(&StackFreeList);
246 REMOVE(LIST_HEAD(&StackFreeList));
247 stacksize = CONFIG_KERN_DEFSTACKSIZE;
248 #elif CONFIG_KERN_HEAP
249 /* Did the caller provide a stack for us? */
252 /* Did the caller specify the desired stack size? */
254 stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
256 /* Allocate stack dinamically */
257 if (!(stack_base = heap_alloc(stacksize)))
263 /* Stack must have been provided by the user */
268 #if CONFIG_KERN_MONITOR
269 /* Fill-in the stack with a special marker to help debugging */
270 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
273 /* Initialize the process control block */
274 if (CPU_STACK_GROWS_UPWARD)
276 proc = (Process*)stack_base;
277 proc->stack = stack_base + proc_size_words;
278 if (CPU_SP_ON_EMPTY_SLOT)
283 proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
284 proc->stack = (cpustack_t*)proc;
285 if (CPU_SP_ON_EMPTY_SLOT)
289 proc_init_struct(proc);
290 proc->user_data = data;
293 proc->stack_base = stack_base;
294 proc->stack_size = stack_size;
296 proc->flags |= PF_FREESTACK;
299 /* Initialize process stack frame */
300 CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
301 CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
303 /* Push a clean set of CPU registers for asm_switch_context() */
304 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
305 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
307 /* Add to ready list */
308 ATOMIC(SCHED_ENQUEUE(proc));
310 #if CONFIG_KERN_MONITOR
311 monitor_add(proc, name, stack_base, stacksize);
317 /** Rename a process */
318 void proc_rename(struct Process *proc, const char *name)
320 #if CONFIG_KERN_MONITOR
321 monitor_rename(proc, name);
323 (void)proc; (void)name;
329 * System scheduler: pass CPU control to the next process in
332 * Saving and restoring the context on the stack is done
333 * by a CPU-dependent support routine which must usually be
334 * written in assembly.
336 void proc_schedule(void)
338 /* This function must not have any "auto" variables, otherwise
339 * the compiler might put them on the stack of the process
340 * being switched out.
342 static struct Process *old_process;
343 static cpuflags_t flags;
345 /* Remember old process to save its context later */
346 old_process = CurrentProcess;
349 /* Scheduling in interrupts is a nono. */
350 ASSERT(!IRQ_RUNNING());
353 /* Poll on the ready queue for the first ready process */
354 IRQ_SAVE_DISABLE(flags);
355 while (!(CurrentProcess = (struct Process *)list_remHead(&ProcReadyList)))
358 * Make sure we physically reenable interrupts here, no matter what
359 * the current task status is. This is important because if we
360 * are idle-spinning, we must allow interrupts, otherwise no
361 * process will ever wake up.
363 * \todo If there was a way to write sig_wait() so that it does not
364 * disable interrupts while waiting, there would not be any
374 * Optimization: don't switch contexts when the active
375 * process has not changed.
377 if (CurrentProcess != old_process)
379 static cpustack_t *dummy;
381 #if CONFIG_KERN_PREEMPTIVE
382 /* Reset quantum for this process */
383 Quantum = CONFIG_KERN_QUANTUM;
386 /* Save context of old process and switch to new process. If there is no
387 * old process, we save the old stack pointer into a dummy variable that
388 * we ignore. In fact, this happens only when the old process has just
390 * TODO: Instead of physically clearing the process at exit time, a zombie
391 * list should be created.
393 asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
396 /* This RET resumes the execution on the new process */
401 * Terminate the current process
405 #if CONFIG_KERN_MONITOR
406 monitor_remove(CurrentProcess);
411 * The following code is BROKEN.
412 * We are freeing our own stack before entering proc_schedule()
413 * BAJO: A correct fix would be to rearrange the scheduler with
414 * an additional parameter which frees the old stack/process
415 * after a context switch.
417 if (CurrentProcess->flags & PF_FREESTACK)
418 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
419 heap_free(CurrentProcess);
422 #if (ARCH & ARCH_EMUL)
423 #warning This is wrong
424 /* Reinsert process stack in free list */
425 ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
426 - (CONFIG_KERN_DEFSTACKSIZE / sizeof(cpustack_t))));
429 * NOTE: At this point the first two words of what used
430 * to be our stack contain a list node. From now on, we
431 * rely on the compiler not reading/writing the stack.
433 #endif /* ARCH_EMUL */
435 CurrentProcess = NULL;
442 * Co-operative context switch
444 void proc_switch(void)
446 /* Just like proc_schedule, this function must not have auto variables. */
447 static cpuflags_t flags;
449 IRQ_SAVE_DISABLE(flags);
450 SCHED_ENQUEUE(CurrentProcess);
458 * Get the pointer to the current process
460 struct Process *proc_current(void)
462 return CurrentProcess;
466 * Get the pointer to the user data of the current process
468 iptr_t proc_current_user_data(void)
470 return CurrentProcess->user_data;
474 #if CONFIG_KERN_PREEMPTIVE
477 * Disable preemptive task switching.
479 * The scheduler maintains a per-process nesting counter. Task switching is
480 * effectively re-enabled only when the number of calls to proc_permit()
481 * matches the number of calls to proc_forbid().
483 * Calling functions that could sleep while task switching is disabled
484 * is dangerous, although supported. Preemptive task switching is
485 * resumed while the process is sleeping and disabled again as soon as
490 void proc_forbid(void)
492 /* No need to protect against interrupts here. */
493 ++CurrentProcess->forbid_cnt;
497 * Re-enable preemptive task switching.
501 void proc_permit(void)
503 /* No need to protect against interrupts here. */
504 --CurrentProcess->forbid_cnt;
507 #endif /* CONFIG_KERN_PREEMPTIVE */