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 1.22 2004/12/13 11:51:08 bernie
21 *#* DISABLE_INTS/ENABLE_INTS: Convert to IRQ_DISABLE/IRQ_ENABLE.
23 *#* Revision 1.21 2004/11/28 23:20:25 bernie
24 *#* Remove obsolete INITLIST macro.
26 *#* Revision 1.20 2004/11/16 22:37:14 bernie
27 *#* Replace IPTR with iptr_t.
29 *#* Revision 1.19 2004/10/19 11:47:39 bernie
30 *#* Kill warnings when !CONFIG_PROC_MONITOR.
32 *#* Revision 1.18 2004/10/19 08:54:43 bernie
33 *#* Initialize forbid_cnt; Formatting/comments fixes.
35 *#* Revision 1.17 2004/10/19 08:47:13 bernie
36 *#* proc_rename(), proc_forbid(), proc_permit(): New functions.
38 *#* Revision 1.16 2004/10/03 20:39:28 bernie
39 *#* Import changes from sc/firmware.
41 *#* Revision 1.15 2004/09/20 03:29:39 bernie
44 *#* Revision 1.14 2004/09/14 21:06:44 bernie
45 *#* Use debug.h instead of kdebug.h.
47 *#* Revision 1.13 2004/08/29 21:58:53 bernie
48 *#* Include macros.h explicityl.
50 *#* Revision 1.11 2004/08/24 16:09:08 bernie
51 *#* Add missing header.
53 *#* Revision 1.10 2004/08/24 16:07:01 bernie
54 *#* Use kputs()/kputchar() when possible.
56 *#* Revision 1.9 2004/08/24 14:26:57 bernie
57 *#* monitor_debug_stacks(): Conditionally compile on CONFIG_KERN_MONITOR.
59 *#* Revision 1.8 2004/08/14 19:37:57 rasky
60 *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
62 *#* Revision 1.7 2004/08/02 20:20:29 aleph
63 *#* Merge from project_ks
65 *#* Revision 1.6 2004/07/30 14:24:16 rasky
66 *#* Task switching con salvataggio perfetto stato di interrupt (SR)
67 *#* Kernel monitor per dump informazioni su stack dei processi
69 *#* Revision 1.5 2004/07/14 14:18:09 rasky
70 *#* Merge da SC: Rimosso timer dentro il task, che รจ uno spreco di memoria per troppi task
72 *#* Revision 1.4 2004/07/13 19:21:28 aleph
73 *#* Avoid warning for unused arg when compiled without some CONFIG_KERN_xx options
75 *#* Revision 1.3 2004/06/06 18:37:57 bernie
76 *#* Rename event macros to look like regular functions.
78 *#* Revision 1.2 2004/06/03 11:27:09 bernie
79 *#* Add dual-license information.
81 *#* Revision 1.1 2004/05/23 17:27:00 bernie
82 *#* Import kern/ subdirectory.
92 #include <arch_config.h> /* ARCH_EMUL */
93 #include <macros.h> /* ABS() */
95 #include <string.h> /* memset() */
98 * CPU dependent context switching routines.
100 * \note This function *MUST* preserve also the status of the interrupts.
102 EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
103 EXTERN_C int asm_switch_version(void);
106 * The scheduer tracks ready and waiting processes
107 * by enqueuing them in these lists. A pointer to the currently
108 * running process is stored in the CurrentProcess pointer.
110 * NOTE: these variables are protected by DI/EI locking
112 REGISTER Process *CurrentProcess;
113 REGISTER List ProcReadyList;
116 #if CONFIG_KERN_PREEMPTIVE
118 * The time sharing scheduler forces a task switch when
119 * the current process has consumed its quantum.
125 /* In Win32 we must emulate stack on the real process stack */
126 #if (ARCH & ARCH_EMUL)
127 extern List StackFreeList;
130 /*! The main process (the one that executes main()). */
131 struct Process MainProcess;
134 static void proc_init_struct(Process *proc)
136 /* Avoid warning for unused argument. */
139 #if CONFIG_KERN_SIGNALS
143 #if CONFIG_KERN_PREEMPTIVE
144 proc->forbid_cnt = 0;
155 LIST_INIT(&ProcReadyList);
157 #if CONFIG_KERN_MONITOR
161 /* We "promote" the current context into a real process. The only thing we have
162 * to do is create a PCB and make it current. We don't need to setup the stack
163 * pointer because it will be written the first time we switch to another process.
165 proc_init_struct(&MainProcess);
166 CurrentProcess = &MainProcess;
168 /* Make sure the assembly routine is up-to-date with us */
169 ASSERT(asm_switch_version() == 1);
174 * Create a new process, starting at the provided entry point.
176 * \return Process structure of new created process
177 * if successful, NULL otherwise.
179 struct Process *proc_new_with_name(UNUSED(const char*, name), void (*entry)(void), iptr_t data, size_t stacksize, cpustack_t *stack_base)
184 size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
186 bool free_stack = false;
189 #if (ARCH & ARCH_EMUL)
190 /* Ignore stack provided by caller and use the large enough default instead. */
191 stack_base = (cpustack_t *)StackFreeList.head;
192 REMOVE((Node *)stack_base);
193 stacksize = DEF_STACKSIZE;
194 #elif CONFIG_KERN_HEAP
195 /* Did the caller provide a stack for us? */
198 /* Did the caller specify the desired stack size? */
200 stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
202 /* Allocate stack dinamically */
203 if (!(stack_base = heap_alloc(stacksize)))
209 /* Stack must have been provided by the user */
214 #if CONFIG_KERN_MONITOR
215 /* Fill-in the stack with a special marker to help debugging */
216 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
219 /* Initialize the process control block */
220 if (CPU_STACK_GROWS_UPWARD)
222 proc = (Process*)stack_base;
223 proc->stack = stack_base + proc_size_words;
224 if (CPU_SP_ON_EMPTY_SLOT)
229 proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
230 proc->stack = (cpustack_t*)proc;
231 if (CPU_SP_ON_EMPTY_SLOT)
235 proc_init_struct(proc);
236 proc->user_data = data;
239 proc->stack_base = stack_base;
240 proc->stack_size = stack_size;
242 proc->flags |= PF_FREESTACK;
245 /* Initialize process stack frame */
246 CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
247 CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
249 /* Push a clean set of CPU registers for asm_switch_context() */
250 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
251 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
253 /* Add to ready list */
254 DISABLE_IRQSAVE(flags);
256 ENABLE_IRQRESTORE(flags);
258 #if CONFIG_KERN_MONITOR
259 monitor_add(proc, name, stack_base, stacksize);
265 /*! Rename a process */
266 void proc_rename(struct Process *proc, const char *name)
268 #if CONFIG_KERN_MONITOR
269 monitor_rename(proc, name);
271 (void)proc; (void)name;
277 * System scheduler: pass CPU control to the next process in
280 * Saving and restoring the context on the stack is done
281 * by a CPU-dependent support routine which must usually be
282 * written in assembly.
284 void proc_schedule(void)
286 /* This function must not have any "auto" variables, otherwise
287 * the compiler might put them on the stack of the process
288 * being switched out.
290 static struct Process *old_process;
291 static cpuflags_t flags;
293 /* Remember old process to save its context later */
294 old_process = CurrentProcess;
296 /* Poll on the ready queue for the first ready process */
297 DISABLE_IRQSAVE(flags);
298 while (!(CurrentProcess = (struct Process *)REMHEAD(&ProcReadyList)))
301 * Make sure we physically reenable interrupts here, no matter what
302 * the current task status is. This is important because if we
303 * are idle-spinning, we must allow interrupts, otherwise no
304 * process will ever wake up.
306 * \todo If there was a way to write sig_wait() so that it does not
307 * disable interrupts while waiting, there would not be any
314 ENABLE_IRQRESTORE(flags);
317 * Optimization: don't switch contexts when the active
318 * process has not changed.
320 if (CurrentProcess != old_process)
322 static cpustack_t *dummy;
324 #if CONFIG_KERN_PREEMPTIVE
325 /* Reset quantum for this process */
326 Quantum = CONFIG_KERN_QUANTUM;
329 /* Save context of old process and switch to new process. If there is no
330 * old process, we save the old stack pointer into a dummy variable that
331 * we ignore. In fact, this happens only when the old process has just
333 * TODO: Instead of physically clearing the process at exit time, a zombie
334 * list should be created.
336 asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
339 /* This RET resumes the execution on the new process */
344 * Terminate the current process
349 /* The following code is BROKEN.
350 * We are freeing our own stack before entering proc_schedule()
351 * BAJO: A correct fix would be to rearrange the scheduler with
352 * an additional parameter which frees the old stack/process
353 * after a context switch.
355 if (CurrentProcess->flags & PF_FREESTACK)
356 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
357 heap_free(CurrentProcess);
360 #if (ARCH & ARCH_EMUL)
362 /* Reinsert process stack in free list */
363 ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
364 - (DEF_STACKSIZE / sizeof(cpustack_t))));
366 /* NOTE: At this point the first two words of what used
367 * to be our stack contain a list node. From now on, we
368 * rely on the compiler not reading/writing the stack.
370 #endif /* ARCH_EMUL */
372 #if CONFIG_KERN_MONITOR
373 monitor_remove(CurrentProcess);
376 CurrentProcess = NULL;
383 * Co-operative context switch
385 void proc_switch(void)
387 /* Just like proc_schedule, this function must not have auto variables. */
388 static cpuflags_t flags;
390 DISABLE_IRQSAVE(flags);
391 SCHED_ENQUEUE(CurrentProcess);
392 ENABLE_IRQRESTORE(flags);
399 * Get the pointer to the current process
401 struct Process *proc_current(void)
403 return CurrentProcess;
407 * Get the pointer to the user data of the current process
409 iptr_t proc_current_user_data(void)
411 return CurrentProcess->user_data;
415 #if CONFIG_KERN_PREEMPTIVE
418 * Disable preemptive task switching.
420 * The scheduler maintains a per-process nesting counter. Task switching is
421 * effectively re-enabled only when the number of calls to proc_permit()
422 * matches the number of calls to proc_forbid().
424 * Calling functions that could sleep while task switching is disabled
425 * is dangerous, although supported. Preemptive task switching is
426 * resumed while the process is sleeping and disabled again as soon as
431 void proc_forbid(void)
433 /* No need to protect against interrupts here. */
434 ++CurrentProcess->forbid_cnt;
438 * Re-enable preemptive task switching.
442 void proc_permit(void)
444 /* No need to protect against interrupts here. */
445 --CurrentProcess->forbid_cnt;
448 #endif /* CONFIG_KERN_PREEMPTIVE */
451 #if 0 /* Simple testcase for the scheduler */
453 #include <drv/timer.h>
456 * Proc scheduling test subthread 1
458 static void NORETURN proc_test_thread1(void)
469 * Proc scheduling test subthread 2
471 static void NORETURN proc_test_thread2(void)
481 static cpustack_t proc_test_stack1[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
482 static cpustack_t proc_test_stack2[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
485 * Proc scheduling test
487 void NORETURN proc_test(void)
489 proc_new(proc_test_thread1, NULL, sizeof(proc_test_stack1), proc_test_stack1);
490 proc_new(proc_test_thread2, NULL, sizeof(proc_test_stack2), proc_test_stack2);
491 kputs("Created tasks\n");
494 kdump(proc_test_stack1+sizeof(proc_test_stack1)-64, 64);
496 kdump(proc_test_stack2+sizeof(proc_test_stack1)-64, 64);
500 kputs(">main task\n");