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 1.25 2005/03/15 00:20:54 bernie
21 *#* proc_schedule(): New sanity check.
23 *#* Revision 1.24 2005/01/08 09:20:54 bernie
24 *#* Remove unused variable.
26 *#* Revision 1.23 2004/12/13 12:07:06 bernie
27 *#* DISABLE_IRQSAVE/ENABLE_IRQRESTORE: Convert to IRQ_SAVE_DISABLE/IRQ_RESTORE.
29 *#* Revision 1.22 2004/12/13 11:51:08 bernie
30 *#* DISABLE_INTS/ENABLE_INTS: Convert to IRQ_DISABLE/IRQ_ENABLE.
32 *#* Revision 1.21 2004/11/28 23:20:25 bernie
33 *#* Remove obsolete INITLIST macro.
35 *#* Revision 1.20 2004/11/16 22:37:14 bernie
36 *#* Replace IPTR with iptr_t.
38 *#* Revision 1.19 2004/10/19 11:47:39 bernie
39 *#* Kill warnings when !CONFIG_PROC_MONITOR.
41 *#* Revision 1.18 2004/10/19 08:54:43 bernie
42 *#* Initialize forbid_cnt; Formatting/comments fixes.
44 *#* Revision 1.17 2004/10/19 08:47:13 bernie
45 *#* proc_rename(), proc_forbid(), proc_permit(): New functions.
47 *#* Revision 1.16 2004/10/03 20:39:28 bernie
48 *#* Import changes from sc/firmware.
50 *#* Revision 1.15 2004/09/20 03:29:39 bernie
53 *#* Revision 1.14 2004/09/14 21:06:44 bernie
54 *#* Use debug.h instead of kdebug.h.
56 *#* Revision 1.13 2004/08/29 21:58:53 bernie
57 *#* Include macros.h explicityl.
59 *#* Revision 1.11 2004/08/24 16:09:08 bernie
60 *#* Add missing header.
62 *#* Revision 1.10 2004/08/24 16:07:01 bernie
63 *#* Use kputs()/kputchar() when possible.
65 *#* Revision 1.9 2004/08/24 14:26:57 bernie
66 *#* monitor_debug_stacks(): Conditionally compile on CONFIG_KERN_MONITOR.
68 *#* Revision 1.8 2004/08/14 19:37:57 rasky
69 *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
71 *#* Revision 1.7 2004/08/02 20:20:29 aleph
72 *#* Merge from project_ks
74 *#* Revision 1.6 2004/07/30 14:24:16 rasky
75 *#* Task switching con salvataggio perfetto stato di interrupt (SR)
76 *#* Kernel monitor per dump informazioni su stack dei processi
78 *#* Revision 1.5 2004/07/14 14:18:09 rasky
79 *#* Merge da SC: Rimosso timer dentro il task, che รจ uno spreco di memoria per troppi task
81 *#* Revision 1.4 2004/07/13 19:21:28 aleph
82 *#* Avoid warning for unused arg when compiled without some CONFIG_KERN_xx options
84 *#* Revision 1.3 2004/06/06 18:37:57 bernie
85 *#* Rename event macros to look like regular functions.
87 *#* Revision 1.2 2004/06/03 11:27:09 bernie
88 *#* Add dual-license information.
90 *#* Revision 1.1 2004/05/23 17:27:00 bernie
91 *#* Import kern/ subdirectory.
101 #include <arch_config.h> /* ARCH_EMUL */
102 #include <macros.h> /* ABS() */
104 #include <string.h> /* memset() */
107 * CPU dependent context switching routines.
109 * \note This function *MUST* preserve also the status of the interrupts.
111 EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
112 EXTERN_C int asm_switch_version(void);
115 * The scheduer tracks ready and waiting processes
116 * by enqueuing them in these lists. A pointer to the currently
117 * running process is stored in the CurrentProcess pointer.
119 * NOTE: these variables are protected by DI/EI locking
121 REGISTER Process *CurrentProcess;
122 REGISTER List ProcReadyList;
125 #if CONFIG_KERN_PREEMPTIVE
127 * The time sharing scheduler forces a task switch when
128 * the current process has consumed its quantum.
134 /* In Win32 we must emulate stack on the real process stack */
135 #if (ARCH & ARCH_EMUL)
136 extern List StackFreeList;
139 /*! The main process (the one that executes main()). */
140 struct Process MainProcess;
143 static void proc_init_struct(Process *proc)
145 /* Avoid warning for unused argument. */
148 #if CONFIG_KERN_SIGNALS
152 #if CONFIG_KERN_PREEMPTIVE
153 proc->forbid_cnt = 0;
164 LIST_INIT(&ProcReadyList);
166 #if CONFIG_KERN_MONITOR
170 /* We "promote" the current context into a real process. The only thing we have
171 * to do is create a PCB and make it current. We don't need to setup the stack
172 * pointer because it will be written the first time we switch to another process.
174 proc_init_struct(&MainProcess);
175 CurrentProcess = &MainProcess;
177 /* Make sure the assembly routine is up-to-date with us */
178 ASSERT(asm_switch_version() == 1);
183 * Create a new process, starting at the provided entry point.
185 * \return Process structure of new created process
186 * if successful, NULL otherwise.
188 struct Process *proc_new_with_name(UNUSED(const char*, name), void (*entry)(void), iptr_t data, size_t stacksize, cpustack_t *stack_base)
192 size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
194 bool free_stack = false;
197 #if (ARCH & ARCH_EMUL)
198 /* Ignore stack provided by caller and use the large enough default instead. */
199 stack_base = (cpustack_t *)StackFreeList.head;
200 REMOVE((Node *)stack_base);
201 stacksize = DEF_STACKSIZE;
202 #elif CONFIG_KERN_HEAP
203 /* Did the caller provide a stack for us? */
206 /* Did the caller specify the desired stack size? */
208 stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
210 /* Allocate stack dinamically */
211 if (!(stack_base = heap_alloc(stacksize)))
217 /* Stack must have been provided by the user */
222 #if CONFIG_KERN_MONITOR
223 /* Fill-in the stack with a special marker to help debugging */
224 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
227 /* Initialize the process control block */
228 if (CPU_STACK_GROWS_UPWARD)
230 proc = (Process*)stack_base;
231 proc->stack = stack_base + proc_size_words;
232 if (CPU_SP_ON_EMPTY_SLOT)
237 proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
238 proc->stack = (cpustack_t*)proc;
239 if (CPU_SP_ON_EMPTY_SLOT)
243 proc_init_struct(proc);
244 proc->user_data = data;
247 proc->stack_base = stack_base;
248 proc->stack_size = stack_size;
250 proc->flags |= PF_FREESTACK;
253 /* Initialize process stack frame */
254 CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
255 CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
257 /* Push a clean set of CPU registers for asm_switch_context() */
258 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
259 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
261 /* Add to ready list */
262 ATOMIC(SCHED_ENQUEUE(proc));
264 #if CONFIG_KERN_MONITOR
265 monitor_add(proc, name, stack_base, stacksize);
271 /*! Rename a process */
272 void proc_rename(struct Process *proc, const char *name)
274 #if CONFIG_KERN_MONITOR
275 monitor_rename(proc, name);
277 (void)proc; (void)name;
283 * System scheduler: pass CPU control to the next process in
286 * Saving and restoring the context on the stack is done
287 * by a CPU-dependent support routine which must usually be
288 * written in assembly.
290 void proc_schedule(void)
292 /* This function must not have any "auto" variables, otherwise
293 * the compiler might put them on the stack of the process
294 * being switched out.
296 static struct Process *old_process;
297 static cpuflags_t flags;
299 /* Remember old process to save its context later */
300 old_process = CurrentProcess;
302 /* Scheduling in interrupts is a nono. */
303 ASSERT(!IRQ_RUNNING());
305 /* Poll on the ready queue for the first ready process */
306 IRQ_SAVE_DISABLE(flags);
307 while (!(CurrentProcess = (struct Process *)REMHEAD(&ProcReadyList)))
310 * Make sure we physically reenable interrupts here, no matter what
311 * the current task status is. This is important because if we
312 * are idle-spinning, we must allow interrupts, otherwise no
313 * process will ever wake up.
315 * \todo If there was a way to write sig_wait() so that it does not
316 * disable interrupts while waiting, there would not be any
326 * Optimization: don't switch contexts when the active
327 * process has not changed.
329 if (CurrentProcess != old_process)
331 static cpustack_t *dummy;
333 #if CONFIG_KERN_PREEMPTIVE
334 /* Reset quantum for this process */
335 Quantum = CONFIG_KERN_QUANTUM;
338 /* Save context of old process and switch to new process. If there is no
339 * old process, we save the old stack pointer into a dummy variable that
340 * we ignore. In fact, this happens only when the old process has just
342 * TODO: Instead of physically clearing the process at exit time, a zombie
343 * list should be created.
345 asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
348 /* This RET resumes the execution on the new process */
353 * Terminate the current process
358 /* The following code is BROKEN.
359 * We are freeing our own stack before entering proc_schedule()
360 * BAJO: A correct fix would be to rearrange the scheduler with
361 * an additional parameter which frees the old stack/process
362 * after a context switch.
364 if (CurrentProcess->flags & PF_FREESTACK)
365 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
366 heap_free(CurrentProcess);
369 #if (ARCH & ARCH_EMUL)
371 /* Reinsert process stack in free list */
372 ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
373 - (DEF_STACKSIZE / sizeof(cpustack_t))));
375 /* NOTE: At this point the first two words of what used
376 * to be our stack contain a list node. From now on, we
377 * rely on the compiler not reading/writing the stack.
379 #endif /* ARCH_EMUL */
381 #if CONFIG_KERN_MONITOR
382 monitor_remove(CurrentProcess);
385 CurrentProcess = NULL;
392 * Co-operative context switch
394 void proc_switch(void)
396 /* Just like proc_schedule, this function must not have auto variables. */
397 static cpuflags_t flags;
399 IRQ_SAVE_DISABLE(flags);
400 SCHED_ENQUEUE(CurrentProcess);
408 * Get the pointer to the current process
410 struct Process *proc_current(void)
412 return CurrentProcess;
416 * Get the pointer to the user data of the current process
418 iptr_t proc_current_user_data(void)
420 return CurrentProcess->user_data;
424 #if CONFIG_KERN_PREEMPTIVE
427 * Disable preemptive task switching.
429 * The scheduler maintains a per-process nesting counter. Task switching is
430 * effectively re-enabled only when the number of calls to proc_permit()
431 * matches the number of calls to proc_forbid().
433 * Calling functions that could sleep while task switching is disabled
434 * is dangerous, although supported. Preemptive task switching is
435 * resumed while the process is sleeping and disabled again as soon as
440 void proc_forbid(void)
442 /* No need to protect against interrupts here. */
443 ++CurrentProcess->forbid_cnt;
447 * Re-enable preemptive task switching.
451 void proc_permit(void)
453 /* No need to protect against interrupts here. */
454 --CurrentProcess->forbid_cnt;
457 #endif /* CONFIG_KERN_PREEMPTIVE */
460 #if 0 /* Simple testcase for the scheduler */
462 #include <drv/timer.h>
465 * Proc scheduling test subthread 1
467 static void NORETURN proc_test_thread1(void)
478 * Proc scheduling test subthread 2
480 static void NORETURN proc_test_thread2(void)
490 static cpustack_t proc_test_stack1[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
491 static cpustack_t proc_test_stack2[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
494 * Proc scheduling test
496 void NORETURN proc_test(void)
498 proc_new(proc_test_thread1, NULL, sizeof(proc_test_stack1), proc_test_stack1);
499 proc_new(proc_test_thread2, NULL, sizeof(proc_test_stack2), proc_test_stack2);
500 kputs("Created tasks\n");
503 kdump(proc_test_stack1+sizeof(proc_test_stack1)-64, 64);
505 kdump(proc_test_stack2+sizeof(proc_test_stack1)-64, 64);
509 kputs(">main task\n");