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 devlib/README 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 1.19 2004/10/19 11:47:39 bernie
21 *#* Kill warnings when !CONFIG_PROC_MONITOR.
23 *#* Revision 1.18 2004/10/19 08:54:43 bernie
24 *#* Initialize forbid_cnt; Formatting/comments fixes.
26 *#* Revision 1.17 2004/10/19 08:47:13 bernie
27 *#* proc_rename(), proc_forbid(), proc_permit(): New functions.
29 *#* Revision 1.16 2004/10/03 20:39:28 bernie
30 *#* Import changes from sc/firmware.
32 *#* Revision 1.15 2004/09/20 03:29:39 bernie
35 *#* Revision 1.14 2004/09/14 21:06:44 bernie
36 *#* Use debug.h instead of kdebug.h.
38 *#* Revision 1.13 2004/08/29 21:58:53 bernie
39 *#* Include macros.h explicityl.
41 *#* Revision 1.11 2004/08/24 16:09:08 bernie
42 *#* Add missing header.
44 *#* Revision 1.10 2004/08/24 16:07:01 bernie
45 *#* Use kputs()/kputchar() when possible.
47 *#* Revision 1.9 2004/08/24 14:26:57 bernie
48 *#* monitor_debug_stacks(): Conditionally compile on CONFIG_KERN_MONITOR.
50 *#* Revision 1.8 2004/08/14 19:37:57 rasky
51 *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
53 *#* Revision 1.7 2004/08/02 20:20:29 aleph
54 *#* Merge from project_ks
56 *#* Revision 1.6 2004/07/30 14:24:16 rasky
57 *#* Task switching con salvataggio perfetto stato di interrupt (SR)
58 *#* Kernel monitor per dump informazioni su stack dei processi
60 *#* Revision 1.5 2004/07/14 14:18:09 rasky
61 *#* Merge da SC: Rimosso timer dentro il task, che รจ uno spreco di memoria per troppi task
63 *#* Revision 1.4 2004/07/13 19:21:28 aleph
64 *#* Avoid warning for unused arg when compiled without some CONFIG_KERN_xx options
66 *#* Revision 1.3 2004/06/06 18:37:57 bernie
67 *#* Rename event macros to look like regular functions.
69 *#* Revision 1.2 2004/06/03 11:27:09 bernie
70 *#* Add dual-license information.
72 *#* Revision 1.1 2004/05/23 17:27:00 bernie
73 *#* Import kern/ subdirectory.
83 #include <arch_config.h> /* ARCH_EMUL */
84 #include <macros.h> /* ABS() */
86 #include <string.h> /* memset() */
89 * CPU dependent context switching routines.
91 * \note This function *MUST* preserve also the status of the interrupts.
93 EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
94 EXTERN_C int asm_switch_version(void);
97 * The scheduer tracks ready and waiting processes
98 * by enqueuing them in these lists. A pointer to the currently
99 * running process is stored in the CurrentProcess pointer.
101 * NOTE: these variables are protected by DI/EI locking
103 REGISTER Process *CurrentProcess;
104 REGISTER List ProcReadyList;
107 #if CONFIG_KERN_PREEMPTIVE
109 * The time sharing scheduler forces a task switch when
110 * the current process has consumed its quantum.
116 /* In Win32 we must emulate stack on the real process stack */
117 #if (ARCH & ARCH_EMUL)
118 extern List StackFreeList;
121 /*! The main process (the one that executes main()). */
122 struct Process MainProcess;
125 static void proc_init_struct(Process *proc)
127 /* Avoid warning for unused argument. */
130 #if CONFIG_KERN_SIGNALS
134 #if CONFIG_KERN_PREEMPTIVE
135 proc->forbid_cnt = 0;
146 INITLIST(&ProcReadyList);
148 #if CONFIG_KERN_MONITOR
152 /* We "promote" the current context into a real process. The only thing we have
153 * to do is create a PCB and make it current. We don't need to setup the stack
154 * pointer because it will be written the first time we switch to another process.
156 proc_init_struct(&MainProcess);
157 CurrentProcess = &MainProcess;
159 /* Make sure the assembly routine is up-to-date with us */
160 ASSERT(asm_switch_version() == 1);
165 * Create a new process, starting at the provided entry point.
167 * \return Process structure of new created process
168 * if successful, NULL otherwise.
170 struct Process *proc_new_with_name(UNUSED(const char*, name), void (*entry)(void), IPTR data, size_t stacksize, cpustack_t *stack_base)
175 size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
177 bool free_stack = false;
180 #if (ARCH & ARCH_EMUL)
181 /* Ignore stack provided by caller and use the large enough default instead. */
182 stack_base = (cpustack_t *)StackFreeList.head;
183 REMOVE((Node *)stack_base);
184 stacksize = DEF_STACKSIZE;
185 #elif CONFIG_KERN_HEAP
186 /* Did the caller provide a stack for us? */
189 /* Did the caller specify the desired stack size? */
191 stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
193 /* Allocate stack dinamically */
194 if (!(stack_base = heap_alloc(stacksize)))
200 /* Stack must have been provided by the user */
205 #if CONFIG_KERN_MONITOR
206 /* Fill-in the stack with a special marker to help debugging */
207 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
210 /* Initialize the process control block */
211 if (CPU_STACK_GROWS_UPWARD)
213 proc = (Process*)stack_base;
214 proc->stack = stack_base + proc_size_words;
215 if (CPU_SP_ON_EMPTY_SLOT)
220 proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
221 proc->stack = (cpustack_t*)proc;
222 if (CPU_SP_ON_EMPTY_SLOT)
226 proc_init_struct(proc);
227 proc->user_data = data;
230 proc->stack_base = stack_base;
231 proc->stack_size = stack_size;
233 proc->flags |= PF_FREESTACK;
236 /* Initialize process stack frame */
237 CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
238 CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
240 /* Push a clean set of CPU registers for asm_switch_context() */
241 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
242 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
244 /* Add to ready list */
245 DISABLE_IRQSAVE(flags);
247 ENABLE_IRQRESTORE(flags);
249 #if CONFIG_KERN_MONITOR
250 monitor_add(proc, name, stack_base, stacksize);
256 /*! Rename a process */
257 void proc_rename(struct Process *proc, const char *name)
259 #if CONFIG_KERN_MONITOR
260 monitor_rename(proc, name);
262 (void)proc; (void)name;
268 * System scheduler: pass CPU control to the next process in
271 * Saving and restoring the context on the stack is done
272 * by a CPU-dependent support routine which must usually be
273 * written in assembly.
275 void proc_schedule(void)
277 /* This function must not have any "auto" variables, otherwise
278 * the compiler might put them on the stack of the process
279 * being switched out.
281 static Process *old_process;
282 static cpuflags_t flags;
284 /* Remember old process to save its context later */
285 old_process = CurrentProcess;
287 /* Poll on the ready queue for the first ready process */
288 DISABLE_IRQSAVE(flags);
289 while (!(CurrentProcess = (struct Process*)REMHEAD(&ProcReadyList)))
292 * Make sure we physically reenable interrupts here, no matter what
293 * the current task status is. This is important because if we
294 * are idle-spinning, we must allow interrupts, otherwise no
295 * process will ever wake up.
297 * \todo If there was a way to code sig_wait so that it does not
298 * disable interrupts while waiting, there would not be any
305 ENABLE_IRQRESTORE(flags);
307 /* Optimization: don't switch contexts when the active
308 * process has not changed.
310 if (CurrentProcess != old_process)
312 static cpustack_t* dummy;
314 #if CONFIG_KERN_PREEMPTIVE
315 /* Reset quantum for this process */
316 Quantum = CONFIG_KERN_QUANTUM;
319 /* Save context of old process and switch to new process. If there is no
320 * old process, we save the old stack pointer into a dummy variable that
321 * we ignore. In fact, this happens only when the old process has just
323 * TODO: Instead of physically clearing the process at exit time, a zombie
324 * list should be created.
326 asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
329 /* This RET resumes the execution on the new process */
334 * Terminate the current process
339 /* The following code is BROKEN.
340 * We are freeing our own stack before entering proc_schedule()
341 * BAJO: A correct fix would be to rearrange the scheduler with
342 * an additional parameter which frees the old stack/process
343 * after a context switch.
345 if (CurrentProcess->flags & PF_FREESTACK)
346 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
347 heap_free(CurrentProcess);
350 #if (ARCH & ARCH_EMUL)
352 /* Reinsert process stack in free list */
353 ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
354 - (DEF_STACKSIZE / sizeof(cpustack_t))));
356 /* NOTE: At this point the first two words of what used
357 * to be our stack contain a list node. From now on, we
358 * rely on the compiler not reading/writing the stack.
360 #endif /* ARCH_EMUL */
362 #if CONFIG_KERN_MONITOR
363 monitor_remove(CurrentProcess);
366 CurrentProcess = NULL;
373 * Co-operative context switch
375 void proc_switch(void)
377 /* Just like proc_schedule, this function must not have auto variables. */
378 static cpuflags_t flags;
380 DISABLE_IRQSAVE(flags);
381 SCHED_ENQUEUE(CurrentProcess);
382 ENABLE_IRQRESTORE(flags);
389 * Get the pointer to the current process
391 struct Process *proc_current(void)
393 return CurrentProcess;
397 * Get the pointer to the user data of the current process
399 IPTR proc_current_user_data(void)
401 return CurrentProcess->user_data;
405 #if CONFIG_KERN_PREEMPTIVE
408 * Disable preemptive task switching.
410 * The scheduler maintains a per-process nesting counter. Task switching is
411 * effectively re-enabled only when the number of calls to proc_permit()
412 * matches the number of calls to proc_forbid().
414 * Calling functions that could sleep while task switching is disabled
415 * is dangerous, although supported. Preemptive task switching is
416 * resumed while the process is sleeping and disabled again as soon as
421 void proc_forbid(void)
423 /* No need to protect against interrupts here. */
424 ++CurrentProcess->forbid_cnt;
428 * Re-enable preemptive task switching.
432 void proc_permit(void)
434 /* No need to protect against interrupts here. */
435 --CurrentProcess->forbid_cnt;
438 #endif /* CONFIG_KERN_PREEMPTIVE */
441 #if 0 /* Simple testcase for the scheduler */
443 #include <drv/timer.h>
446 * Proc scheduling test subthread 1
448 static void NORETURN proc_test_thread1(void)
459 * Proc scheduling test subthread 2
461 static void NORETURN proc_test_thread2(void)
471 static cpustack_t proc_test_stack1[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
472 static cpustack_t proc_test_stack2[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
475 * Proc scheduling test
477 void NORETURN proc_test(void)
479 proc_new(proc_test_thread1, NULL, sizeof(proc_test_stack1), proc_test_stack1);
480 proc_new(proc_test_thread2, NULL, sizeof(proc_test_stack2), proc_test_stack2);
481 kputs("Created tasks\n");
484 kdump(proc_test_stack1+sizeof(proc_test_stack1)-64, 64);
486 kdump(proc_test_stack2+sizeof(proc_test_stack1)-64, 64);
490 kputs(">main task\n");