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 1.26 2005/04/11 19:10:28 bernie
21 *#* Include top-level headers from cfg/ subdir.
23 *#* Revision 1.25 2005/03/15 00:20:54 bernie
24 *#* proc_schedule(): New sanity check.
26 *#* Revision 1.24 2005/01/08 09:20:54 bernie
27 *#* Remove unused variable.
29 *#* Revision 1.23 2004/12/13 12:07:06 bernie
30 *#* DISABLE_IRQSAVE/ENABLE_IRQRESTORE: Convert to IRQ_SAVE_DISABLE/IRQ_RESTORE.
32 *#* Revision 1.22 2004/12/13 11:51:08 bernie
33 *#* DISABLE_INTS/ENABLE_INTS: Convert to IRQ_DISABLE/IRQ_ENABLE.
35 *#* Revision 1.21 2004/11/28 23:20:25 bernie
36 *#* Remove obsolete INITLIST macro.
38 *#* Revision 1.20 2004/11/16 22:37:14 bernie
39 *#* Replace IPTR with iptr_t.
41 *#* Revision 1.19 2004/10/19 11:47:39 bernie
42 *#* Kill warnings when !CONFIG_PROC_MONITOR.
44 *#* Revision 1.18 2004/10/19 08:54:43 bernie
45 *#* Initialize forbid_cnt; Formatting/comments fixes.
47 *#* Revision 1.17 2004/10/19 08:47:13 bernie
48 *#* proc_rename(), proc_forbid(), proc_permit(): New functions.
50 *#* Revision 1.16 2004/10/03 20:39:28 bernie
51 *#* Import changes from sc/firmware.
53 *#* Revision 1.15 2004/09/20 03:29:39 bernie
56 *#* Revision 1.14 2004/09/14 21:06:44 bernie
57 *#* Use debug.h instead of kdebug.h.
59 *#* Revision 1.13 2004/08/29 21:58:53 bernie
60 *#* Include macros.h explicityl.
62 *#* Revision 1.11 2004/08/24 16:09:08 bernie
63 *#* Add missing header.
65 *#* Revision 1.10 2004/08/24 16:07:01 bernie
66 *#* Use kputs()/kputchar() when possible.
68 *#* Revision 1.9 2004/08/24 14:26:57 bernie
69 *#* monitor_debug_stacks(): Conditionally compile on CONFIG_KERN_MONITOR.
71 *#* Revision 1.8 2004/08/14 19:37:57 rasky
72 *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
74 *#* Revision 1.7 2004/08/02 20:20:29 aleph
75 *#* Merge from project_ks
77 *#* Revision 1.6 2004/07/30 14:24:16 rasky
78 *#* Task switching con salvataggio perfetto stato di interrupt (SR)
79 *#* Kernel monitor per dump informazioni su stack dei processi
81 *#* Revision 1.5 2004/07/14 14:18:09 rasky
82 *#* Merge da SC: Rimosso timer dentro il task, che รจ uno spreco di memoria per troppi task
84 *#* Revision 1.4 2004/07/13 19:21:28 aleph
85 *#* Avoid warning for unused arg when compiled without some CONFIG_KERN_xx options
87 *#* Revision 1.3 2004/06/06 18:37:57 bernie
88 *#* Rename event macros to look like regular functions.
90 *#* Revision 1.2 2004/06/03 11:27:09 bernie
91 *#* Add dual-license information.
93 *#* Revision 1.1 2004/05/23 17:27:00 bernie
94 *#* Import kern/ subdirectory.
103 #include <cfg/debug.h>
104 #include <cfg/arch_config.h> /* ARCH_EMUL */
105 #include <cfg/macros.h> /* ABS() */
107 #include <string.h> /* memset() */
110 * CPU dependent context switching routines.
112 * \note This function *MUST* preserve also the status of the interrupts.
114 EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
115 EXTERN_C int asm_switch_version(void);
118 * The scheduer tracks ready and waiting processes
119 * by enqueuing them in these lists. A pointer to the currently
120 * running process is stored in the CurrentProcess pointer.
122 * NOTE: these variables are protected by DI/EI locking
124 REGISTER Process *CurrentProcess;
125 REGISTER List ProcReadyList;
128 #if CONFIG_KERN_PREEMPTIVE
130 * The time sharing scheduler forces a task switch when
131 * the current process has consumed its quantum.
137 /* In Win32 we must emulate stack on the real process stack */
138 #if (ARCH & ARCH_EMUL)
139 extern List StackFreeList;
142 /*! The main process (the one that executes main()). */
143 struct Process MainProcess;
146 static void proc_init_struct(Process *proc)
148 /* Avoid warning for unused argument. */
151 #if CONFIG_KERN_SIGNALS
155 #if CONFIG_KERN_PREEMPTIVE
156 proc->forbid_cnt = 0;
167 LIST_INIT(&ProcReadyList);
169 #if CONFIG_KERN_MONITOR
173 /* We "promote" the current context into a real process. The only thing we have
174 * to do is create a PCB and make it current. We don't need to setup the stack
175 * pointer because it will be written the first time we switch to another process.
177 proc_init_struct(&MainProcess);
178 CurrentProcess = &MainProcess;
180 /* Make sure the assembly routine is up-to-date with us */
181 ASSERT(asm_switch_version() == 1);
186 * Create a new process, starting at the provided entry point.
188 * \return Process structure of new created process
189 * if successful, NULL otherwise.
191 struct Process *proc_new_with_name(UNUSED(const char*, name), void (*entry)(void), iptr_t data, size_t stacksize, cpustack_t *stack_base)
195 size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
197 bool free_stack = false;
200 #if (ARCH & ARCH_EMUL)
201 /* Ignore stack provided by caller and use the large enough default instead. */
202 stack_base = (cpustack_t *)StackFreeList.head;
203 REMOVE((Node *)stack_base);
204 stacksize = DEF_STACKSIZE;
205 #elif CONFIG_KERN_HEAP
206 /* Did the caller provide a stack for us? */
209 /* Did the caller specify the desired stack size? */
211 stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
213 /* Allocate stack dinamically */
214 if (!(stack_base = heap_alloc(stacksize)))
220 /* Stack must have been provided by the user */
225 #if CONFIG_KERN_MONITOR
226 /* Fill-in the stack with a special marker to help debugging */
227 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
230 /* Initialize the process control block */
231 if (CPU_STACK_GROWS_UPWARD)
233 proc = (Process*)stack_base;
234 proc->stack = stack_base + proc_size_words;
235 if (CPU_SP_ON_EMPTY_SLOT)
240 proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
241 proc->stack = (cpustack_t*)proc;
242 if (CPU_SP_ON_EMPTY_SLOT)
246 proc_init_struct(proc);
247 proc->user_data = data;
250 proc->stack_base = stack_base;
251 proc->stack_size = stack_size;
253 proc->flags |= PF_FREESTACK;
256 /* Initialize process stack frame */
257 CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
258 CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
260 /* Push a clean set of CPU registers for asm_switch_context() */
261 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
262 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
264 /* Add to ready list */
265 ATOMIC(SCHED_ENQUEUE(proc));
267 #if CONFIG_KERN_MONITOR
268 monitor_add(proc, name, stack_base, stacksize);
274 /*! Rename a process */
275 void proc_rename(struct Process *proc, const char *name)
277 #if CONFIG_KERN_MONITOR
278 monitor_rename(proc, name);
280 (void)proc; (void)name;
286 * System scheduler: pass CPU control to the next process in
289 * Saving and restoring the context on the stack is done
290 * by a CPU-dependent support routine which must usually be
291 * written in assembly.
293 void proc_schedule(void)
295 /* This function must not have any "auto" variables, otherwise
296 * the compiler might put them on the stack of the process
297 * being switched out.
299 static struct Process *old_process;
300 static cpuflags_t flags;
302 /* Remember old process to save its context later */
303 old_process = CurrentProcess;
305 /* Scheduling in interrupts is a nono. */
306 ASSERT(!IRQ_RUNNING());
308 /* Poll on the ready queue for the first ready process */
309 IRQ_SAVE_DISABLE(flags);
310 while (!(CurrentProcess = (struct Process *)REMHEAD(&ProcReadyList)))
313 * Make sure we physically reenable interrupts here, no matter what
314 * the current task status is. This is important because if we
315 * are idle-spinning, we must allow interrupts, otherwise no
316 * process will ever wake up.
318 * \todo If there was a way to write sig_wait() so that it does not
319 * disable interrupts while waiting, there would not be any
329 * Optimization: don't switch contexts when the active
330 * process has not changed.
332 if (CurrentProcess != old_process)
334 static cpustack_t *dummy;
336 #if CONFIG_KERN_PREEMPTIVE
337 /* Reset quantum for this process */
338 Quantum = CONFIG_KERN_QUANTUM;
341 /* Save context of old process and switch to new process. If there is no
342 * old process, we save the old stack pointer into a dummy variable that
343 * we ignore. In fact, this happens only when the old process has just
345 * TODO: Instead of physically clearing the process at exit time, a zombie
346 * list should be created.
348 asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
351 /* This RET resumes the execution on the new process */
356 * Terminate the current process
361 /* The following code is BROKEN.
362 * We are freeing our own stack before entering proc_schedule()
363 * BAJO: A correct fix would be to rearrange the scheduler with
364 * an additional parameter which frees the old stack/process
365 * after a context switch.
367 if (CurrentProcess->flags & PF_FREESTACK)
368 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
369 heap_free(CurrentProcess);
372 #if (ARCH & ARCH_EMUL)
374 /* Reinsert process stack in free list */
375 ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
376 - (DEF_STACKSIZE / sizeof(cpustack_t))));
378 /* NOTE: At this point the first two words of what used
379 * to be our stack contain a list node. From now on, we
380 * rely on the compiler not reading/writing the stack.
382 #endif /* ARCH_EMUL */
384 #if CONFIG_KERN_MONITOR
385 monitor_remove(CurrentProcess);
388 CurrentProcess = NULL;
395 * Co-operative context switch
397 void proc_switch(void)
399 /* Just like proc_schedule, this function must not have auto variables. */
400 static cpuflags_t flags;
402 IRQ_SAVE_DISABLE(flags);
403 SCHED_ENQUEUE(CurrentProcess);
411 * Get the pointer to the current process
413 struct Process *proc_current(void)
415 return CurrentProcess;
419 * Get the pointer to the user data of the current process
421 iptr_t proc_current_user_data(void)
423 return CurrentProcess->user_data;
427 #if CONFIG_KERN_PREEMPTIVE
430 * Disable preemptive task switching.
432 * The scheduler maintains a per-process nesting counter. Task switching is
433 * effectively re-enabled only when the number of calls to proc_permit()
434 * matches the number of calls to proc_forbid().
436 * Calling functions that could sleep while task switching is disabled
437 * is dangerous, although supported. Preemptive task switching is
438 * resumed while the process is sleeping and disabled again as soon as
443 void proc_forbid(void)
445 /* No need to protect against interrupts here. */
446 ++CurrentProcess->forbid_cnt;
450 * Re-enable preemptive task switching.
454 void proc_permit(void)
456 /* No need to protect against interrupts here. */
457 --CurrentProcess->forbid_cnt;
460 #endif /* CONFIG_KERN_PREEMPTIVE */
463 #if 0 /* Simple testcase for the scheduler */
465 #include <drv/timer.h>
468 * Proc scheduling test subthread 1
470 static void NORETURN proc_test_thread1(void)
481 * Proc scheduling test subthread 2
483 static void NORETURN proc_test_thread2(void)
493 static cpustack_t proc_test_stack1[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
494 static cpustack_t proc_test_stack2[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
497 * Proc scheduling test
499 void NORETURN proc_test(void)
501 proc_new(proc_test_thread1, NULL, sizeof(proc_test_stack1), proc_test_stack1);
502 proc_new(proc_test_thread2, NULL, sizeof(proc_test_stack2), proc_test_stack2);
503 kputs("Created tasks\n");
506 kdump(proc_test_stack1+sizeof(proc_test_stack1)-64, 64);
508 kdump(proc_test_stack2+sizeof(proc_test_stack1)-64, 64);
512 kputs(">main task\n");