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 1.21 2004/11/28 23:20:25 bernie
21 *#* Remove obsolete INITLIST macro.
23 *#* Revision 1.20 2004/11/16 22:37:14 bernie
24 *#* Replace IPTR with iptr_t.
26 *#* Revision 1.19 2004/10/19 11:47:39 bernie
27 *#* Kill warnings when !CONFIG_PROC_MONITOR.
29 *#* Revision 1.18 2004/10/19 08:54:43 bernie
30 *#* Initialize forbid_cnt; Formatting/comments fixes.
32 *#* Revision 1.17 2004/10/19 08:47:13 bernie
33 *#* proc_rename(), proc_forbid(), proc_permit(): New functions.
35 *#* Revision 1.16 2004/10/03 20:39:28 bernie
36 *#* Import changes from sc/firmware.
38 *#* Revision 1.15 2004/09/20 03:29:39 bernie
41 *#* Revision 1.14 2004/09/14 21:06:44 bernie
42 *#* Use debug.h instead of kdebug.h.
44 *#* Revision 1.13 2004/08/29 21:58:53 bernie
45 *#* Include macros.h explicityl.
47 *#* Revision 1.11 2004/08/24 16:09:08 bernie
48 *#* Add missing header.
50 *#* Revision 1.10 2004/08/24 16:07:01 bernie
51 *#* Use kputs()/kputchar() when possible.
53 *#* Revision 1.9 2004/08/24 14:26:57 bernie
54 *#* monitor_debug_stacks(): Conditionally compile on CONFIG_KERN_MONITOR.
56 *#* Revision 1.8 2004/08/14 19:37:57 rasky
57 *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
59 *#* Revision 1.7 2004/08/02 20:20:29 aleph
60 *#* Merge from project_ks
62 *#* Revision 1.6 2004/07/30 14:24:16 rasky
63 *#* Task switching con salvataggio perfetto stato di interrupt (SR)
64 *#* Kernel monitor per dump informazioni su stack dei processi
66 *#* Revision 1.5 2004/07/14 14:18:09 rasky
67 *#* Merge da SC: Rimosso timer dentro il task, che รจ uno spreco di memoria per troppi task
69 *#* Revision 1.4 2004/07/13 19:21:28 aleph
70 *#* Avoid warning for unused arg when compiled without some CONFIG_KERN_xx options
72 *#* Revision 1.3 2004/06/06 18:37:57 bernie
73 *#* Rename event macros to look like regular functions.
75 *#* Revision 1.2 2004/06/03 11:27:09 bernie
76 *#* Add dual-license information.
78 *#* Revision 1.1 2004/05/23 17:27:00 bernie
79 *#* Import kern/ subdirectory.
89 #include <arch_config.h> /* ARCH_EMUL */
90 #include <macros.h> /* ABS() */
92 #include <string.h> /* memset() */
95 * CPU dependent context switching routines.
97 * \note This function *MUST* preserve also the status of the interrupts.
99 EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
100 EXTERN_C int asm_switch_version(void);
103 * The scheduer tracks ready and waiting processes
104 * by enqueuing them in these lists. A pointer to the currently
105 * running process is stored in the CurrentProcess pointer.
107 * NOTE: these variables are protected by DI/EI locking
109 REGISTER Process *CurrentProcess;
110 REGISTER List ProcReadyList;
113 #if CONFIG_KERN_PREEMPTIVE
115 * The time sharing scheduler forces a task switch when
116 * the current process has consumed its quantum.
122 /* In Win32 we must emulate stack on the real process stack */
123 #if (ARCH & ARCH_EMUL)
124 extern List StackFreeList;
127 /*! The main process (the one that executes main()). */
128 struct Process MainProcess;
131 static void proc_init_struct(Process *proc)
133 /* Avoid warning for unused argument. */
136 #if CONFIG_KERN_SIGNALS
140 #if CONFIG_KERN_PREEMPTIVE
141 proc->forbid_cnt = 0;
152 LIST_INIT(&ProcReadyList);
154 #if CONFIG_KERN_MONITOR
158 /* We "promote" the current context into a real process. The only thing we have
159 * to do is create a PCB and make it current. We don't need to setup the stack
160 * pointer because it will be written the first time we switch to another process.
162 proc_init_struct(&MainProcess);
163 CurrentProcess = &MainProcess;
165 /* Make sure the assembly routine is up-to-date with us */
166 ASSERT(asm_switch_version() == 1);
171 * Create a new process, starting at the provided entry point.
173 * \return Process structure of new created process
174 * if successful, NULL otherwise.
176 struct Process *proc_new_with_name(UNUSED(const char*, name), void (*entry)(void), iptr_t data, size_t stacksize, cpustack_t *stack_base)
181 size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
183 bool free_stack = false;
186 #if (ARCH & ARCH_EMUL)
187 /* Ignore stack provided by caller and use the large enough default instead. */
188 stack_base = (cpustack_t *)StackFreeList.head;
189 REMOVE((Node *)stack_base);
190 stacksize = DEF_STACKSIZE;
191 #elif CONFIG_KERN_HEAP
192 /* Did the caller provide a stack for us? */
195 /* Did the caller specify the desired stack size? */
197 stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
199 /* Allocate stack dinamically */
200 if (!(stack_base = heap_alloc(stacksize)))
206 /* Stack must have been provided by the user */
211 #if CONFIG_KERN_MONITOR
212 /* Fill-in the stack with a special marker to help debugging */
213 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
216 /* Initialize the process control block */
217 if (CPU_STACK_GROWS_UPWARD)
219 proc = (Process*)stack_base;
220 proc->stack = stack_base + proc_size_words;
221 if (CPU_SP_ON_EMPTY_SLOT)
226 proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
227 proc->stack = (cpustack_t*)proc;
228 if (CPU_SP_ON_EMPTY_SLOT)
232 proc_init_struct(proc);
233 proc->user_data = data;
236 proc->stack_base = stack_base;
237 proc->stack_size = stack_size;
239 proc->flags |= PF_FREESTACK;
242 /* Initialize process stack frame */
243 CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
244 CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
246 /* Push a clean set of CPU registers for asm_switch_context() */
247 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
248 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
250 /* Add to ready list */
251 DISABLE_IRQSAVE(flags);
253 ENABLE_IRQRESTORE(flags);
255 #if CONFIG_KERN_MONITOR
256 monitor_add(proc, name, stack_base, stacksize);
262 /*! Rename a process */
263 void proc_rename(struct Process *proc, const char *name)
265 #if CONFIG_KERN_MONITOR
266 monitor_rename(proc, name);
268 (void)proc; (void)name;
274 * System scheduler: pass CPU control to the next process in
277 * Saving and restoring the context on the stack is done
278 * by a CPU-dependent support routine which must usually be
279 * written in assembly.
281 void proc_schedule(void)
283 /* This function must not have any "auto" variables, otherwise
284 * the compiler might put them on the stack of the process
285 * being switched out.
287 static Process *old_process;
288 static cpuflags_t flags;
290 /* Remember old process to save its context later */
291 old_process = CurrentProcess;
293 /* Poll on the ready queue for the first ready process */
294 DISABLE_IRQSAVE(flags);
295 while (!(CurrentProcess = (struct Process*)REMHEAD(&ProcReadyList)))
298 * Make sure we physically reenable interrupts here, no matter what
299 * the current task status is. This is important because if we
300 * are idle-spinning, we must allow interrupts, otherwise no
301 * process will ever wake up.
303 * \todo If there was a way to code sig_wait so that it does not
304 * disable interrupts while waiting, there would not be any
311 ENABLE_IRQRESTORE(flags);
313 /* Optimization: don't switch contexts when the active
314 * process has not changed.
316 if (CurrentProcess != old_process)
318 static cpustack_t* dummy;
320 #if CONFIG_KERN_PREEMPTIVE
321 /* Reset quantum for this process */
322 Quantum = CONFIG_KERN_QUANTUM;
325 /* Save context of old process and switch to new process. If there is no
326 * old process, we save the old stack pointer into a dummy variable that
327 * we ignore. In fact, this happens only when the old process has just
329 * TODO: Instead of physically clearing the process at exit time, a zombie
330 * list should be created.
332 asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
335 /* This RET resumes the execution on the new process */
340 * Terminate the current process
345 /* The following code is BROKEN.
346 * We are freeing our own stack before entering proc_schedule()
347 * BAJO: A correct fix would be to rearrange the scheduler with
348 * an additional parameter which frees the old stack/process
349 * after a context switch.
351 if (CurrentProcess->flags & PF_FREESTACK)
352 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
353 heap_free(CurrentProcess);
356 #if (ARCH & ARCH_EMUL)
358 /* Reinsert process stack in free list */
359 ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
360 - (DEF_STACKSIZE / sizeof(cpustack_t))));
362 /* NOTE: At this point the first two words of what used
363 * to be our stack contain a list node. From now on, we
364 * rely on the compiler not reading/writing the stack.
366 #endif /* ARCH_EMUL */
368 #if CONFIG_KERN_MONITOR
369 monitor_remove(CurrentProcess);
372 CurrentProcess = NULL;
379 * Co-operative context switch
381 void proc_switch(void)
383 /* Just like proc_schedule, this function must not have auto variables. */
384 static cpuflags_t flags;
386 DISABLE_IRQSAVE(flags);
387 SCHED_ENQUEUE(CurrentProcess);
388 ENABLE_IRQRESTORE(flags);
395 * Get the pointer to the current process
397 struct Process *proc_current(void)
399 return CurrentProcess;
403 * Get the pointer to the user data of the current process
405 iptr_t proc_current_user_data(void)
407 return CurrentProcess->user_data;
411 #if CONFIG_KERN_PREEMPTIVE
414 * Disable preemptive task switching.
416 * The scheduler maintains a per-process nesting counter. Task switching is
417 * effectively re-enabled only when the number of calls to proc_permit()
418 * matches the number of calls to proc_forbid().
420 * Calling functions that could sleep while task switching is disabled
421 * is dangerous, although supported. Preemptive task switching is
422 * resumed while the process is sleeping and disabled again as soon as
427 void proc_forbid(void)
429 /* No need to protect against interrupts here. */
430 ++CurrentProcess->forbid_cnt;
434 * Re-enable preemptive task switching.
438 void proc_permit(void)
440 /* No need to protect against interrupts here. */
441 --CurrentProcess->forbid_cnt;
444 #endif /* CONFIG_KERN_PREEMPTIVE */
447 #if 0 /* Simple testcase for the scheduler */
449 #include <drv/timer.h>
452 * Proc scheduling test subthread 1
454 static void NORETURN proc_test_thread1(void)
465 * Proc scheduling test subthread 2
467 static void NORETURN proc_test_thread2(void)
477 static cpustack_t proc_test_stack1[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
478 static cpustack_t proc_test_stack2[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
481 * Proc scheduling test
483 void NORETURN proc_test(void)
485 proc_new(proc_test_thread1, NULL, sizeof(proc_test_stack1), proc_test_stack1);
486 proc_new(proc_test_thread2, NULL, sizeof(proc_test_stack2), proc_test_stack2);
487 kputs("Created tasks\n");
490 kdump(proc_test_stack1+sizeof(proc_test_stack1)-64, 64);
492 kdump(proc_test_stack2+sizeof(proc_test_stack1)-64, 64);
496 kputs(">main task\n");