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 1.28 2006/02/21 16:06:55 bernie
21 *#* Cleanup/update process scheduling.
23 *#* Revision 1.27 2005/11/04 16:20:02 bernie
24 *#* Fix reference to README.devlib in header.
26 *#* Revision 1.26 2005/04/11 19:10:28 bernie
27 *#* Include top-level headers from cfg/ subdir.
29 *#* Revision 1.25 2005/03/15 00:20:54 bernie
30 *#* proc_schedule(): New sanity check.
32 *#* Revision 1.24 2005/01/08 09:20:54 bernie
33 *#* Remove unused variable.
35 *#* Revision 1.23 2004/12/13 12:07:06 bernie
36 *#* DISABLE_IRQSAVE/ENABLE_IRQRESTORE: Convert to IRQ_SAVE_DISABLE/IRQ_RESTORE.
38 *#* Revision 1.22 2004/12/13 11:51:08 bernie
39 *#* DISABLE_INTS/ENABLE_INTS: Convert to IRQ_DISABLE/IRQ_ENABLE.
41 *#* Revision 1.21 2004/11/28 23:20:25 bernie
42 *#* Remove obsolete INITLIST macro.
44 *#* Revision 1.20 2004/11/16 22:37:14 bernie
45 *#* Replace IPTR with iptr_t.
47 *#* Revision 1.19 2004/10/19 11:47:39 bernie
48 *#* Kill warnings when !CONFIG_PROC_MONITOR.
50 *#* Revision 1.18 2004/10/19 08:54:43 bernie
51 *#* Initialize forbid_cnt; Formatting/comments fixes.
53 *#* Revision 1.17 2004/10/19 08:47:13 bernie
54 *#* proc_rename(), proc_forbid(), proc_permit(): New functions.
56 *#* Revision 1.16 2004/10/03 20:39:28 bernie
57 *#* Import changes from sc/firmware.
59 *#* Revision 1.15 2004/09/20 03:29:39 bernie
62 *#* Revision 1.14 2004/09/14 21:06:44 bernie
63 *#* Use debug.h instead of kdebug.h.
65 *#* Revision 1.13 2004/08/29 21:58:53 bernie
66 *#* Include macros.h explicityl.
68 *#* Revision 1.11 2004/08/24 16:09:08 bernie
69 *#* Add missing header.
71 *#* Revision 1.10 2004/08/24 16:07:01 bernie
72 *#* Use kputs()/kputchar() when possible.
74 *#* Revision 1.9 2004/08/24 14:26:57 bernie
75 *#* monitor_debug_stacks(): Conditionally compile on CONFIG_KERN_MONITOR.
77 *#* Revision 1.8 2004/08/14 19:37:57 rasky
78 *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
80 *#* Revision 1.7 2004/08/02 20:20:29 aleph
81 *#* Merge from project_ks
83 *#* Revision 1.6 2004/07/30 14:24:16 rasky
84 *#* Task switching con salvataggio perfetto stato di interrupt (SR)
85 *#* Kernel monitor per dump informazioni su stack dei processi
87 *#* Revision 1.5 2004/07/14 14:18:09 rasky
88 *#* Merge da SC: Rimosso timer dentro il task, che รจ uno spreco di memoria per troppi task
90 *#* Revision 1.4 2004/07/13 19:21:28 aleph
91 *#* Avoid warning for unused arg when compiled without some CONFIG_KERN_xx options
93 *#* Revision 1.3 2004/06/06 18:37:57 bernie
94 *#* Rename event macros to look like regular functions.
96 *#* Revision 1.2 2004/06/03 11:27:09 bernie
97 *#* Add dual-license information.
99 *#* Revision 1.1 2004/05/23 17:27:00 bernie
100 *#* Import kern/ subdirectory.
107 #include <mware/event.h>
109 #include <cfg/debug.h>
110 #include <cfg/arch_config.h> /* ARCH_EMUL */
111 #include <cfg/macros.h> /* ABS() */
113 #include <string.h> /* memset() */
116 * CPU dependent context switching routines.
118 * \note This function *MUST* preserve also the status of the interrupts.
120 EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
121 EXTERN_C int asm_switch_version(void);
124 * The scheduer tracks ready and waiting processes
125 * by enqueuing them in these lists. A pointer to the currently
126 * running process is stored in the CurrentProcess pointer.
128 * NOTE: these variables are protected by DI/EI locking
130 REGISTER Process *CurrentProcess;
131 REGISTER List ProcReadyList;
134 #if CONFIG_KERN_PREEMPTIVE
136 * The time sharing scheduler forces a task switch when
137 * the current process has consumed its quantum.
143 /* In Win32 we must emulate stack on the real process stack */
144 #if (ARCH & ARCH_EMUL)
145 extern List StackFreeList;
148 /*! The main process (the one that executes main()). */
149 struct Process MainProcess;
152 static void proc_init_struct(Process *proc)
154 /* Avoid warning for unused argument. */
157 #if CONFIG_KERN_SIGNALS
161 #if CONFIG_KERN_PREEMPTIVE
162 proc->forbid_cnt = 0;
173 LIST_INIT(&ProcReadyList);
175 #if CONFIG_KERN_MONITOR
179 /* We "promote" the current context into a real process. The only thing we have
180 * to do is create a PCB and make it current. We don't need to setup the stack
181 * pointer because it will be written the first time we switch to another process.
183 proc_init_struct(&MainProcess);
184 CurrentProcess = &MainProcess;
186 /* Make sure the assembly routine is up-to-date with us */
187 ASSERT(asm_switch_version() == 1);
192 * Create a new process, starting at the provided entry point.
194 * \return Process structure of new created process
195 * if successful, NULL otherwise.
197 struct Process *proc_new_with_name(UNUSED(const char *, name), void (*entry)(void), iptr_t data, size_t stacksize, cpustack_t *stack_base)
201 size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
203 bool free_stack = false;
206 #if (ARCH & ARCH_EMUL)
207 /* Ignore stack provided by caller and use the large enough default instead. */
208 stack_base = (cpustack_t *)LIST_HEAD(&StackFreeList);
209 REMOVE(LIST_HEAD(&StackFreeList));
210 stacksize = CONFIG_KERN_DEFSTACKSIZE;
211 #elif CONFIG_KERN_HEAP
212 /* Did the caller provide a stack for us? */
215 /* Did the caller specify the desired stack size? */
217 stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
219 /* Allocate stack dinamically */
220 if (!(stack_base = heap_alloc(stacksize)))
226 /* Stack must have been provided by the user */
231 #if CONFIG_KERN_MONITOR
232 /* Fill-in the stack with a special marker to help debugging */
233 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
236 /* Initialize the process control block */
237 if (CPU_STACK_GROWS_UPWARD)
239 proc = (Process*)stack_base;
240 proc->stack = stack_base + proc_size_words;
241 if (CPU_SP_ON_EMPTY_SLOT)
246 proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
247 proc->stack = (cpustack_t*)proc;
248 if (CPU_SP_ON_EMPTY_SLOT)
252 proc_init_struct(proc);
253 proc->user_data = data;
256 proc->stack_base = stack_base;
257 proc->stack_size = stack_size;
259 proc->flags |= PF_FREESTACK;
262 /* Initialize process stack frame */
263 CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
264 CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
266 /* Push a clean set of CPU registers for asm_switch_context() */
267 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
268 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
270 /* Add to ready list */
271 ATOMIC(SCHED_ENQUEUE(proc));
273 #if CONFIG_KERN_MONITOR
274 monitor_add(proc, name, stack_base, stacksize);
280 /*! Rename a process */
281 void proc_rename(struct Process *proc, const char *name)
283 #if CONFIG_KERN_MONITOR
284 monitor_rename(proc, name);
286 (void)proc; (void)name;
292 * System scheduler: pass CPU control to the next process in
295 * Saving and restoring the context on the stack is done
296 * by a CPU-dependent support routine which must usually be
297 * written in assembly.
299 void proc_schedule(void)
301 /* This function must not have any "auto" variables, otherwise
302 * the compiler might put them on the stack of the process
303 * being switched out.
305 static struct Process *old_process;
306 static cpuflags_t flags;
308 /* Remember old process to save its context later */
309 old_process = CurrentProcess;
311 /* Scheduling in interrupts is a nono. */
312 ASSERT(!IRQ_RUNNING());
314 /* Poll on the ready queue for the first ready process */
315 IRQ_SAVE_DISABLE(flags);
316 while (!(CurrentProcess = (struct Process *)REMHEAD(&ProcReadyList)))
319 * Make sure we physically reenable interrupts here, no matter what
320 * the current task status is. This is important because if we
321 * are idle-spinning, we must allow interrupts, otherwise no
322 * process will ever wake up.
324 * \todo If there was a way to write sig_wait() so that it does not
325 * disable interrupts while waiting, there would not be any
335 * Optimization: don't switch contexts when the active
336 * process has not changed.
338 if (CurrentProcess != old_process)
340 static cpustack_t *dummy;
342 #if CONFIG_KERN_PREEMPTIVE
343 /* Reset quantum for this process */
344 Quantum = CONFIG_KERN_QUANTUM;
347 /* Save context of old process and switch to new process. If there is no
348 * old process, we save the old stack pointer into a dummy variable that
349 * we ignore. In fact, this happens only when the old process has just
351 * TODO: Instead of physically clearing the process at exit time, a zombie
352 * list should be created.
354 asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
357 /* This RET resumes the execution on the new process */
362 * Terminate the current process
366 #if CONFIG_KERN_MONITOR
367 monitor_remove(CurrentProcess);
372 * The following code is BROKEN.
373 * We are freeing our own stack before entering proc_schedule()
374 * BAJO: A correct fix would be to rearrange the scheduler with
375 * an additional parameter which frees the old stack/process
376 * after a context switch.
378 if (CurrentProcess->flags & PF_FREESTACK)
379 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
380 heap_free(CurrentProcess);
383 #if (ARCH & ARCH_EMUL)
384 #warning This is wrong
385 /* Reinsert process stack in free list */
386 ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
387 - (CONFIG_KERN_DEFSTACKSIZE / sizeof(cpustack_t))));
390 * NOTE: At this point the first two words of what used
391 * to be our stack contain a list node. From now on, we
392 * rely on the compiler not reading/writing the stack.
394 #endif /* ARCH_EMUL */
396 CurrentProcess = NULL;
403 * Co-operative context switch
405 void proc_switch(void)
407 /* Just like proc_schedule, this function must not have auto variables. */
408 static cpuflags_t flags;
410 IRQ_SAVE_DISABLE(flags);
411 SCHED_ENQUEUE(CurrentProcess);
419 * Get the pointer to the current process
421 struct Process *proc_current(void)
423 return CurrentProcess;
427 * Get the pointer to the user data of the current process
429 iptr_t proc_current_user_data(void)
431 return CurrentProcess->user_data;
435 #if CONFIG_KERN_PREEMPTIVE
438 * Disable preemptive task switching.
440 * The scheduler maintains a per-process nesting counter. Task switching is
441 * effectively re-enabled only when the number of calls to proc_permit()
442 * matches the number of calls to proc_forbid().
444 * Calling functions that could sleep while task switching is disabled
445 * is dangerous, although supported. Preemptive task switching is
446 * resumed while the process is sleeping and disabled again as soon as
451 void proc_forbid(void)
453 /* No need to protect against interrupts here. */
454 ++CurrentProcess->forbid_cnt;
458 * Re-enable preemptive task switching.
462 void proc_permit(void)
464 /* No need to protect against interrupts here. */
465 --CurrentProcess->forbid_cnt;
468 #endif /* CONFIG_KERN_PREEMPTIVE */
471 #if 0 /* Simple testcase for the scheduler */
473 #include <drv/timer.h>
476 * Proc scheduling test subthread 1
478 static void NORETURN proc_test_thread1(void)
489 * Proc scheduling test subthread 2
491 static void NORETURN proc_test_thread2(void)
501 static cpustack_t proc_test_stack1[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
502 static cpustack_t proc_test_stack2[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
505 * Proc scheduling test
507 void NORETURN proc_test(void)
509 proc_new(proc_test_thread1, NULL, sizeof(proc_test_stack1), proc_test_stack1);
510 proc_new(proc_test_thread2, NULL, sizeof(proc_test_stack2), proc_test_stack2);
511 kputs("Created tasks\n");
514 kdump(proc_test_stack1+sizeof(proc_test_stack1)-64, 64);
516 kdump(proc_test_stack2+sizeof(proc_test_stack1)-64, 64);
520 kputs(">main task\n");