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 1.18 2004/10/19 08:54:43 bernie
21 *#* Initialize forbid_cnt; Formatting/comments fixes.
23 *#* Revision 1.17 2004/10/19 08:47:13 bernie
24 *#* proc_rename(), proc_forbid(), proc_permit(): New functions.
26 *#* Revision 1.16 2004/10/03 20:39:28 bernie
27 *#* Import changes from sc/firmware.
29 *#* Revision 1.15 2004/09/20 03:29:39 bernie
32 *#* Revision 1.14 2004/09/14 21:06:44 bernie
33 *#* Use debug.h instead of kdebug.h.
35 *#* Revision 1.13 2004/08/29 21:58:53 bernie
36 *#* Include macros.h explicityl.
38 *#* Revision 1.11 2004/08/24 16:09:08 bernie
39 *#* Add missing header.
41 *#* Revision 1.10 2004/08/24 16:07:01 bernie
42 *#* Use kputs()/kputchar() when possible.
44 *#* Revision 1.9 2004/08/24 14:26:57 bernie
45 *#* monitor_debug_stacks(): Conditionally compile on CONFIG_KERN_MONITOR.
47 *#* Revision 1.8 2004/08/14 19:37:57 rasky
48 *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
50 *#* Revision 1.7 2004/08/02 20:20:29 aleph
51 *#* Merge from project_ks
53 *#* Revision 1.6 2004/07/30 14:24:16 rasky
54 *#* Task switching con salvataggio perfetto stato di interrupt (SR)
55 *#* Kernel monitor per dump informazioni su stack dei processi
57 *#* Revision 1.5 2004/07/14 14:18:09 rasky
58 *#* Merge da SC: Rimosso timer dentro il task, che รจ uno spreco di memoria per troppi task
60 *#* Revision 1.4 2004/07/13 19:21:28 aleph
61 *#* Avoid warning for unused arg when compiled without some CONFIG_KERN_xx options
63 *#* Revision 1.3 2004/06/06 18:37:57 bernie
64 *#* Rename event macros to look like regular functions.
66 *#* Revision 1.2 2004/06/03 11:27:09 bernie
67 *#* Add dual-license information.
69 *#* Revision 1.1 2004/05/23 17:27:00 bernie
70 *#* Import kern/ subdirectory.
80 #include <arch_config.h> /* ARCH_EMUL */
81 #include <macros.h> /* ABS() */
83 #include <string.h> /* memset() */
86 * CPU dependent context switching routines.
88 * \note This function *MUST* preserve also the status of the interrupts.
90 EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
91 EXTERN_C int asm_switch_version(void);
94 * The scheduer tracks ready and waiting processes
95 * by enqueuing them in these lists. A pointer to the currently
96 * running process is stored in the CurrentProcess pointer.
98 * NOTE: these variables are protected by DI/EI locking
100 REGISTER Process *CurrentProcess;
101 REGISTER List ProcReadyList;
104 #if CONFIG_KERN_PREEMPTIVE
106 * The time sharing scheduler forces a task switch when
107 * the current process has consumed its quantum.
113 /* In Win32 we must emulate stack on the real process stack */
114 #if (ARCH & ARCH_EMUL)
115 extern List StackFreeList;
118 /*! The main process (the one that executes main()). */
119 struct Process MainProcess;
122 static void proc_init_struct(Process *proc)
124 /* Avoid warning for unused argument. */
127 #if CONFIG_KERN_SIGNALS
131 #if CONFIG_KERN_PREEMPTIVE
132 proc->forbid_cnt = 0;
143 INITLIST(&ProcReadyList);
145 #if CONFIG_KERN_MONITOR
149 /* We "promote" the current context into a real process. The only thing we have
150 * to do is create a PCB and make it current. We don't need to setup the stack
151 * pointer because it will be written the first time we switch to another process.
153 proc_init_struct(&MainProcess);
154 CurrentProcess = &MainProcess;
156 /* Make sure the assembly routine is up-to-date with us */
157 ASSERT(asm_switch_version() == 1);
162 * Create a new process, starting at the provided entry point.
164 * \return Process structure of new created process
165 * if successful, NULL otherwise.
167 struct Process *proc_new_with_name(UNUSED(const char*, name), void (*entry)(void), IPTR data, size_t stacksize, cpustack_t *stack_base)
172 size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
174 bool free_stack = false;
177 #if (ARCH & ARCH_EMUL)
178 /* Ignore stack provided by caller and use the large enough default instead. */
179 stack_base = (cpustack_t *)StackFreeList.head;
180 REMOVE((Node *)stack_base);
181 stacksize = DEF_STACKSIZE;
182 #elif CONFIG_KERN_HEAP
183 /* Did the caller provide a stack for us? */
186 /* Did the caller specify the desired stack size? */
188 stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
190 /* Allocate stack dinamically */
191 if (!(stack_base = heap_alloc(stacksize)))
197 /* Stack must have been provided by the user */
202 #if CONFIG_KERN_MONITOR
203 /* Fill-in the stack with a special marker to help debugging */
204 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
207 /* Initialize the process control block */
208 if (CPU_STACK_GROWS_UPWARD)
210 proc = (Process*)stack_base;
211 proc->stack = stack_base + proc_size_words;
212 if (CPU_SP_ON_EMPTY_SLOT)
217 proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
218 proc->stack = (cpustack_t*)proc;
219 if (CPU_SP_ON_EMPTY_SLOT)
223 proc_init_struct(proc);
224 proc->user_data = data;
227 proc->stack_base = stack_base;
228 proc->stack_size = stack_size;
230 proc->flags |= PF_FREESTACK;
233 /* Initialize process stack frame */
234 CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
235 CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
237 /* Push a clean set of CPU registers for asm_switch_context() */
238 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
239 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
241 /* Add to ready list */
242 DISABLE_IRQSAVE(flags);
244 ENABLE_IRQRESTORE(flags);
246 #if CONFIG_KERN_MONITOR
247 monitor_add(proc, name, stack_base, stacksize);
253 /*! Rename a process */
254 void proc_rename(struct Process *proc, const char *name)
256 #if CONFIG_KERN_MONITOR
257 monitor_rename(proc, name);
263 * System scheduler: pass CPU control to the next process in
266 * Saving and restoring the context on the stack is done
267 * by a CPU-dependent support routine which must usually be
268 * written in assembly.
270 void proc_schedule(void)
272 /* This function must not have any "auto" variables, otherwise
273 * the compiler might put them on the stack of the process
274 * being switched out.
276 static Process *old_process;
277 static cpuflags_t flags;
279 /* Remember old process to save its context later */
280 old_process = CurrentProcess;
282 /* Poll on the ready queue for the first ready process */
283 DISABLE_IRQSAVE(flags);
284 while (!(CurrentProcess = (struct Process*)REMHEAD(&ProcReadyList)))
287 * Make sure we physically reenable interrupts here, no matter what
288 * the current task status is. This is important because if we
289 * are idle-spinning, we must allow interrupts, otherwise no
290 * process will ever wake up.
292 * \todo If there was a way to code sig_wait so that it does not
293 * disable interrupts while waiting, there would not be any
300 ENABLE_IRQRESTORE(flags);
302 /* Optimization: don't switch contexts when the active
303 * process has not changed.
305 if (CurrentProcess != old_process)
307 static cpustack_t* dummy;
309 #if CONFIG_KERN_PREEMPTIVE
310 /* Reset quantum for this process */
311 Quantum = CONFIG_KERN_QUANTUM;
314 /* Save context of old process and switch to new process. If there is no
315 * old process, we save the old stack pointer into a dummy variable that
316 * we ignore. In fact, this happens only when the old process has just
318 * TODO: Instead of physically clearing the process at exit time, a zombie
319 * list should be created.
321 asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
324 /* This RET resumes the execution on the new process */
329 * Terminate the current process
334 /* The following code is BROKEN.
335 * We are freeing our own stack before entering proc_schedule()
336 * BAJO: A correct fix would be to rearrange the scheduler with
337 * an additional parameter which frees the old stack/process
338 * after a context switch.
340 if (CurrentProcess->flags & PF_FREESTACK)
341 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
342 heap_free(CurrentProcess);
345 #if (ARCH & ARCH_EMUL)
347 /* Reinsert process stack in free list */
348 ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
349 - (DEF_STACKSIZE / sizeof(cpustack_t))));
351 /* NOTE: At this point the first two words of what used
352 * to be our stack contain a list node. From now on, we
353 * rely on the compiler not reading/writing the stack.
355 #endif /* ARCH_EMUL */
357 #if CONFIG_KERN_MONITOR
358 monitor_remove(CurrentProcess);
361 CurrentProcess = NULL;
368 * Co-operative context switch
370 void proc_switch(void)
372 /* Just like proc_schedule, this function must not have auto variables. */
373 static cpuflags_t flags;
375 DISABLE_IRQSAVE(flags);
376 SCHED_ENQUEUE(CurrentProcess);
377 ENABLE_IRQRESTORE(flags);
384 * Get the pointer to the current process
386 struct Process *proc_current(void)
388 return CurrentProcess;
392 * Get the pointer to the user data of the current process
394 IPTR proc_current_user_data(void)
396 return CurrentProcess->user_data;
400 #if CONFIG_KERN_PREEMPTIVE
403 * Disable preemptive task switching.
405 * The scheduler maintains a per-process nesting counter. Task switching is
406 * effectively re-enabled only when the number of calls to proc_permit()
407 * matches the number of calls to proc_forbid().
409 * Calling functions that could sleep while task switching is disabled
410 * is dangerous, although supported. Preemptive task switching is
411 * resumed while the process is sleeping and disabled again as soon as
416 void proc_forbid(void)
418 /* No need to protect against interrupts here. */
419 ++CurrentProcess->forbid_cnt;
423 * Re-enable preemptive task switching.
427 void proc_permit(void)
429 /* No need to protect against interrupts here. */
430 --CurrentProcess->forbid_cnt;
433 #endif /* CONFIG_KERN_PREEMPTIVE */
436 #if 0 /* Simple testcase for the scheduler */
438 #include <drv/timer.h>
441 * Proc scheduling test subthread 1
443 static void NORETURN proc_test_thread1(void)
454 * Proc scheduling test subthread 2
456 static void NORETURN proc_test_thread2(void)
466 static cpustack_t proc_test_stack1[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
467 static cpustack_t proc_test_stack2[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
470 * Proc scheduling test
472 void NORETURN proc_test(void)
474 proc_new(proc_test_thread1, NULL, sizeof(proc_test_stack1), proc_test_stack1);
475 proc_new(proc_test_thread2, NULL, sizeof(proc_test_stack2), proc_test_stack2);
476 kputs("Created tasks\n");
479 kdump(proc_test_stack1+sizeof(proc_test_stack1)-64, 64);
481 kdump(proc_test_stack2+sizeof(proc_test_stack1)-64, 64);
485 kputs(">main task\n");