4 * Copyright 2001,2004 Develer S.r.l. (http://www.develer.com/)
5 * Copyright 1999,2000,2001 Bernardo Innocenti <bernie@develer.com>
6 * This file is part of DevLib - See README.devlib for information.
9 * \brief Simple realtime multitasking scheduler.
10 * Context switching is only done cooperatively.
14 * \author Bernardo Innocenti <bernie@develer.com>
15 * \author Stefano Fedrigo <aleph@develer.com>
20 *#* Revision 1.32 2006/09/20 14:19:23 marco
23 *#* Revision 1.31 2006/07/19 12:56:27 bernie
24 *#* Convert to new Doxygen style.
26 *#* Revision 1.30 2006/03/27 04:49:23 bernie
27 *#* CPU_IDLE(): Fix for new emulator.
29 *#* Revision 1.29 2006/02/24 01:17:05 bernie
30 *#* Update for new emulator.
32 *#* Revision 1.28 2006/02/21 16:06:55 bernie
33 *#* Cleanup/update process scheduling.
35 *#* Revision 1.27 2005/11/04 16:20:02 bernie
36 *#* Fix reference to README.devlib in header.
38 *#* Revision 1.26 2005/04/11 19:10:28 bernie
39 *#* Include top-level headers from cfg/ subdir.
41 *#* Revision 1.25 2005/03/15 00:20:54 bernie
42 *#* proc_schedule(): New sanity check.
44 *#* Revision 1.24 2005/01/08 09:20:54 bernie
45 *#* Remove unused variable.
47 *#* Revision 1.23 2004/12/13 12:07:06 bernie
48 *#* DISABLE_IRQSAVE/ENABLE_IRQRESTORE: Convert to IRQ_SAVE_DISABLE/IRQ_RESTORE.
50 *#* Revision 1.22 2004/12/13 11:51:08 bernie
51 *#* DISABLE_INTS/ENABLE_INTS: Convert to IRQ_DISABLE/IRQ_ENABLE.
53 *#* Revision 1.21 2004/11/28 23:20:25 bernie
54 *#* Remove obsolete INITLIST macro.
56 *#* Revision 1.20 2004/11/16 22:37:14 bernie
57 *#* Replace IPTR with iptr_t.
59 *#* Revision 1.19 2004/10/19 11:47:39 bernie
60 *#* Kill warnings when !CONFIG_PROC_MONITOR.
62 *#* Revision 1.18 2004/10/19 08:54:43 bernie
63 *#* Initialize forbid_cnt; Formatting/comments fixes.
65 *#* Revision 1.17 2004/10/19 08:47:13 bernie
66 *#* proc_rename(), proc_forbid(), proc_permit(): New functions.
68 *#* Revision 1.16 2004/10/03 20:39:28 bernie
69 *#* Import changes from sc/firmware.
71 *#* Revision 1.15 2004/09/20 03:29:39 bernie
74 *#* Revision 1.14 2004/09/14 21:06:44 bernie
75 *#* Use debug.h instead of kdebug.h.
77 *#* Revision 1.13 2004/08/29 21:58:53 bernie
78 *#* Include macros.h explicityl.
80 *#* Revision 1.11 2004/08/24 16:09:08 bernie
81 *#* Add missing header.
83 *#* Revision 1.10 2004/08/24 16:07:01 bernie
84 *#* Use kputs()/kputchar() when possible.
86 *#* Revision 1.9 2004/08/24 14:26:57 bernie
87 *#* monitor_debug_stacks(): Conditionally compile on CONFIG_KERN_MONITOR.
89 *#* Revision 1.8 2004/08/14 19:37:57 rasky
90 *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
92 *#* Revision 1.7 2004/08/02 20:20:29 aleph
93 *#* Merge from project_ks
95 *#* Revision 1.6 2004/07/30 14:24:16 rasky
96 *#* Task switching con salvataggio perfetto stato di interrupt (SR)
97 *#* Kernel monitor per dump informazioni su stack dei processi
99 *#* Revision 1.5 2004/07/14 14:18:09 rasky
100 *#* Merge da SC: Rimosso timer dentro il task, che รจ uno spreco di memoria per troppi task
102 *#* Revision 1.4 2004/07/13 19:21:28 aleph
103 *#* Avoid warning for unused arg when compiled without some CONFIG_KERN_xx options
105 *#* Revision 1.3 2004/06/06 18:37:57 bernie
106 *#* Rename event macros to look like regular functions.
108 *#* Revision 1.2 2004/06/03 11:27:09 bernie
109 *#* Add dual-license information.
111 *#* Revision 1.1 2004/05/23 17:27:00 bernie
112 *#* Import kern/ subdirectory.
119 #include <mware/event.h>
121 #include <cfg/debug.h>
122 #include <cfg/arch_config.h> /* ARCH_EMUL */
123 #include <cfg/macros.h> /* ABS() */
125 #include <string.h> /* memset() */
128 * CPU dependent context switching routines.
130 * \note This function *MUST* preserve also the status of the interrupts.
132 EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
133 EXTERN_C int asm_switch_version(void);
136 * The scheduer tracks ready and waiting processes
137 * by enqueuing them in these lists. A pointer to the currently
138 * running process is stored in the CurrentProcess pointer.
140 * NOTE: these variables are protected by DI/EI locking
142 REGISTER Process *CurrentProcess;
143 REGISTER List ProcReadyList;
146 #if CONFIG_KERN_PREEMPTIVE
148 * The time sharing scheduler forces a task switch when
149 * the current process has consumed its quantum.
155 /* In Win32 we must emulate stack on the real process stack */
156 #if (ARCH & ARCH_EMUL)
157 extern List StackFreeList;
160 /** The main process (the one that executes main()). */
161 struct Process MainProcess;
164 static void proc_init_struct(Process *proc)
166 /* Avoid warning for unused argument. */
169 #if CONFIG_KERN_SIGNALS
173 #if CONFIG_KERN_PREEMPTIVE
174 proc->forbid_cnt = 0;
185 LIST_INIT(&ProcReadyList);
187 #if CONFIG_KERN_MONITOR
191 /* We "promote" the current context into a real process. The only thing we have
192 * to do is create a PCB and make it current. We don't need to setup the stack
193 * pointer because it will be written the first time we switch to another process.
195 proc_init_struct(&MainProcess);
196 CurrentProcess = &MainProcess;
198 /* Make sure the assembly routine is up-to-date with us */
199 ASSERT(asm_switch_version() == 1);
204 * Create a new process, starting at the provided entry point.
206 * \return Process structure of new created process
207 * if successful, NULL otherwise.
209 struct Process *proc_new_with_name(UNUSED(const char *, name), void (*entry)(void), iptr_t data, size_t stacksize, cpustack_t *stack_base)
213 size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
215 bool free_stack = false;
218 #if (ARCH & ARCH_EMUL)
219 /* Ignore stack provided by caller and use the large enough default instead. */
220 stack_base = (cpustack_t *)LIST_HEAD(&StackFreeList);
221 REMOVE(LIST_HEAD(&StackFreeList));
222 stacksize = CONFIG_KERN_DEFSTACKSIZE;
223 #elif CONFIG_KERN_HEAP
224 /* Did the caller provide a stack for us? */
227 /* Did the caller specify the desired stack size? */
229 stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
231 /* Allocate stack dinamically */
232 if (!(stack_base = heap_alloc(stacksize)))
238 /* Stack must have been provided by the user */
243 #if CONFIG_KERN_MONITOR
244 /* Fill-in the stack with a special marker to help debugging */
245 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
248 /* Initialize the process control block */
249 if (CPU_STACK_GROWS_UPWARD)
251 proc = (Process*)stack_base;
252 proc->stack = stack_base + proc_size_words;
253 if (CPU_SP_ON_EMPTY_SLOT)
258 proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
259 proc->stack = (cpustack_t*)proc;
260 if (CPU_SP_ON_EMPTY_SLOT)
264 proc_init_struct(proc);
265 proc->user_data = data;
268 proc->stack_base = stack_base;
269 proc->stack_size = stack_size;
271 proc->flags |= PF_FREESTACK;
274 /* Initialize process stack frame */
275 CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
276 CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
278 /* Push a clean set of CPU registers for asm_switch_context() */
279 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
280 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
282 /* Add to ready list */
283 ATOMIC(SCHED_ENQUEUE(proc));
285 #if CONFIG_KERN_MONITOR
286 monitor_add(proc, name, stack_base, stacksize);
292 /** Rename a process */
293 void proc_rename(struct Process *proc, const char *name)
295 #if CONFIG_KERN_MONITOR
296 monitor_rename(proc, name);
298 (void)proc; (void)name;
304 * System scheduler: pass CPU control to the next process in
307 * Saving and restoring the context on the stack is done
308 * by a CPU-dependent support routine which must usually be
309 * written in assembly.
311 void proc_schedule(void)
313 /* This function must not have any "auto" variables, otherwise
314 * the compiler might put them on the stack of the process
315 * being switched out.
317 static struct Process *old_process;
318 static cpuflags_t flags;
320 /* Remember old process to save its context later */
321 old_process = CurrentProcess;
324 /* Scheduling in interrupts is a nono. */
325 ASSERT(!IRQ_RUNNING());
328 /* Poll on the ready queue for the first ready process */
329 IRQ_SAVE_DISABLE(flags);
330 while (!(CurrentProcess = (struct Process *)list_remHead(&ProcReadyList)))
333 * Make sure we physically reenable interrupts here, no matter what
334 * the current task status is. This is important because if we
335 * are idle-spinning, we must allow interrupts, otherwise no
336 * process will ever wake up.
338 * \todo If there was a way to write sig_wait() so that it does not
339 * disable interrupts while waiting, there would not be any
349 * Optimization: don't switch contexts when the active
350 * process has not changed.
352 if (CurrentProcess != old_process)
354 static cpustack_t *dummy;
356 #if CONFIG_KERN_PREEMPTIVE
357 /* Reset quantum for this process */
358 Quantum = CONFIG_KERN_QUANTUM;
361 /* Save context of old process and switch to new process. If there is no
362 * old process, we save the old stack pointer into a dummy variable that
363 * we ignore. In fact, this happens only when the old process has just
365 * TODO: Instead of physically clearing the process at exit time, a zombie
366 * list should be created.
368 asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
371 /* This RET resumes the execution on the new process */
376 * Terminate the current process
380 #if CONFIG_KERN_MONITOR
381 monitor_remove(CurrentProcess);
386 * The following code is BROKEN.
387 * We are freeing our own stack before entering proc_schedule()
388 * BAJO: A correct fix would be to rearrange the scheduler with
389 * an additional parameter which frees the old stack/process
390 * after a context switch.
392 if (CurrentProcess->flags & PF_FREESTACK)
393 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
394 heap_free(CurrentProcess);
397 #if (ARCH & ARCH_EMUL)
398 #warning This is wrong
399 /* Reinsert process stack in free list */
400 ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
401 - (CONFIG_KERN_DEFSTACKSIZE / sizeof(cpustack_t))));
404 * NOTE: At this point the first two words of what used
405 * to be our stack contain a list node. From now on, we
406 * rely on the compiler not reading/writing the stack.
408 #endif /* ARCH_EMUL */
410 CurrentProcess = NULL;
417 * Co-operative context switch
419 void proc_switch(void)
421 /* Just like proc_schedule, this function must not have auto variables. */
422 static cpuflags_t flags;
424 IRQ_SAVE_DISABLE(flags);
425 SCHED_ENQUEUE(CurrentProcess);
433 * Get the pointer to the current process
435 struct Process *proc_current(void)
437 return CurrentProcess;
441 * Get the pointer to the user data of the current process
443 iptr_t proc_current_user_data(void)
445 return CurrentProcess->user_data;
449 #if CONFIG_KERN_PREEMPTIVE
452 * Disable preemptive task switching.
454 * The scheduler maintains a per-process nesting counter. Task switching is
455 * effectively re-enabled only when the number of calls to proc_permit()
456 * matches the number of calls to proc_forbid().
458 * Calling functions that could sleep while task switching is disabled
459 * is dangerous, although supported. Preemptive task switching is
460 * resumed while the process is sleeping and disabled again as soon as
465 void proc_forbid(void)
467 /* No need to protect against interrupts here. */
468 ++CurrentProcess->forbid_cnt;
472 * Re-enable preemptive task switching.
476 void proc_permit(void)
478 /* No need to protect against interrupts here. */
479 --CurrentProcess->forbid_cnt;
482 #endif /* CONFIG_KERN_PREEMPTIVE */