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 1.30 2006/03/27 04:49:23 bernie
21 *#* CPU_IDLE(): Fix for new emulator.
23 *#* Revision 1.29 2006/02/24 01:17:05 bernie
24 *#* Update for new emulator.
26 *#* Revision 1.28 2006/02/21 16:06:55 bernie
27 *#* Cleanup/update process scheduling.
29 *#* Revision 1.27 2005/11/04 16:20:02 bernie
30 *#* Fix reference to README.devlib in header.
32 *#* Revision 1.26 2005/04/11 19:10:28 bernie
33 *#* Include top-level headers from cfg/ subdir.
35 *#* Revision 1.25 2005/03/15 00:20:54 bernie
36 *#* proc_schedule(): New sanity check.
38 *#* Revision 1.24 2005/01/08 09:20:54 bernie
39 *#* Remove unused variable.
41 *#* Revision 1.23 2004/12/13 12:07:06 bernie
42 *#* DISABLE_IRQSAVE/ENABLE_IRQRESTORE: Convert to IRQ_SAVE_DISABLE/IRQ_RESTORE.
44 *#* Revision 1.22 2004/12/13 11:51:08 bernie
45 *#* DISABLE_INTS/ENABLE_INTS: Convert to IRQ_DISABLE/IRQ_ENABLE.
47 *#* Revision 1.21 2004/11/28 23:20:25 bernie
48 *#* Remove obsolete INITLIST macro.
50 *#* Revision 1.20 2004/11/16 22:37:14 bernie
51 *#* Replace IPTR with iptr_t.
53 *#* Revision 1.19 2004/10/19 11:47:39 bernie
54 *#* Kill warnings when !CONFIG_PROC_MONITOR.
56 *#* Revision 1.18 2004/10/19 08:54:43 bernie
57 *#* Initialize forbid_cnt; Formatting/comments fixes.
59 *#* Revision 1.17 2004/10/19 08:47:13 bernie
60 *#* proc_rename(), proc_forbid(), proc_permit(): New functions.
62 *#* Revision 1.16 2004/10/03 20:39:28 bernie
63 *#* Import changes from sc/firmware.
65 *#* Revision 1.15 2004/09/20 03:29:39 bernie
68 *#* Revision 1.14 2004/09/14 21:06:44 bernie
69 *#* Use debug.h instead of kdebug.h.
71 *#* Revision 1.13 2004/08/29 21:58:53 bernie
72 *#* Include macros.h explicityl.
74 *#* Revision 1.11 2004/08/24 16:09:08 bernie
75 *#* Add missing header.
77 *#* Revision 1.10 2004/08/24 16:07:01 bernie
78 *#* Use kputs()/kputchar() when possible.
80 *#* Revision 1.9 2004/08/24 14:26:57 bernie
81 *#* monitor_debug_stacks(): Conditionally compile on CONFIG_KERN_MONITOR.
83 *#* Revision 1.8 2004/08/14 19:37:57 rasky
84 *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
86 *#* Revision 1.7 2004/08/02 20:20:29 aleph
87 *#* Merge from project_ks
89 *#* Revision 1.6 2004/07/30 14:24:16 rasky
90 *#* Task switching con salvataggio perfetto stato di interrupt (SR)
91 *#* Kernel monitor per dump informazioni su stack dei processi
93 *#* Revision 1.5 2004/07/14 14:18:09 rasky
94 *#* Merge da SC: Rimosso timer dentro il task, che รจ uno spreco di memoria per troppi task
96 *#* Revision 1.4 2004/07/13 19:21:28 aleph
97 *#* Avoid warning for unused arg when compiled without some CONFIG_KERN_xx options
99 *#* Revision 1.3 2004/06/06 18:37:57 bernie
100 *#* Rename event macros to look like regular functions.
102 *#* Revision 1.2 2004/06/03 11:27:09 bernie
103 *#* Add dual-license information.
105 *#* Revision 1.1 2004/05/23 17:27:00 bernie
106 *#* Import kern/ subdirectory.
113 #include <mware/event.h>
115 #include <cfg/debug.h>
116 #include <cfg/arch_config.h> /* ARCH_EMUL */
117 #include <cfg/macros.h> /* ABS() */
119 #include <string.h> /* memset() */
122 * CPU dependent context switching routines.
124 * \note This function *MUST* preserve also the status of the interrupts.
126 EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
127 EXTERN_C int asm_switch_version(void);
130 * The scheduer tracks ready and waiting processes
131 * by enqueuing them in these lists. A pointer to the currently
132 * running process is stored in the CurrentProcess pointer.
134 * NOTE: these variables are protected by DI/EI locking
136 REGISTER Process *CurrentProcess;
137 REGISTER List ProcReadyList;
140 #if CONFIG_KERN_PREEMPTIVE
142 * The time sharing scheduler forces a task switch when
143 * the current process has consumed its quantum.
149 /* In Win32 we must emulate stack on the real process stack */
150 #if (ARCH & ARCH_EMUL)
151 extern List StackFreeList;
154 /*! The main process (the one that executes main()). */
155 struct Process MainProcess;
158 static void proc_init_struct(Process *proc)
160 /* Avoid warning for unused argument. */
163 #if CONFIG_KERN_SIGNALS
167 #if CONFIG_KERN_PREEMPTIVE
168 proc->forbid_cnt = 0;
179 LIST_INIT(&ProcReadyList);
181 #if CONFIG_KERN_MONITOR
185 /* We "promote" the current context into a real process. The only thing we have
186 * to do is create a PCB and make it current. We don't need to setup the stack
187 * pointer because it will be written the first time we switch to another process.
189 proc_init_struct(&MainProcess);
190 CurrentProcess = &MainProcess;
192 /* Make sure the assembly routine is up-to-date with us */
193 ASSERT(asm_switch_version() == 1);
198 * Create a new process, starting at the provided entry point.
200 * \return Process structure of new created process
201 * if successful, NULL otherwise.
203 struct Process *proc_new_with_name(UNUSED(const char *, name), void (*entry)(void), iptr_t data, size_t stacksize, cpustack_t *stack_base)
207 size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
209 bool free_stack = false;
212 #if (ARCH & ARCH_EMUL)
213 /* Ignore stack provided by caller and use the large enough default instead. */
214 stack_base = (cpustack_t *)LIST_HEAD(&StackFreeList);
215 REMOVE(LIST_HEAD(&StackFreeList));
216 stacksize = CONFIG_KERN_DEFSTACKSIZE;
217 #elif CONFIG_KERN_HEAP
218 /* Did the caller provide a stack for us? */
221 /* Did the caller specify the desired stack size? */
223 stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
225 /* Allocate stack dinamically */
226 if (!(stack_base = heap_alloc(stacksize)))
232 /* Stack must have been provided by the user */
237 #if CONFIG_KERN_MONITOR
238 /* Fill-in the stack with a special marker to help debugging */
239 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
242 /* Initialize the process control block */
243 if (CPU_STACK_GROWS_UPWARD)
245 proc = (Process*)stack_base;
246 proc->stack = stack_base + proc_size_words;
247 if (CPU_SP_ON_EMPTY_SLOT)
252 proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
253 proc->stack = (cpustack_t*)proc;
254 if (CPU_SP_ON_EMPTY_SLOT)
258 proc_init_struct(proc);
259 proc->user_data = data;
262 proc->stack_base = stack_base;
263 proc->stack_size = stack_size;
265 proc->flags |= PF_FREESTACK;
268 /* Initialize process stack frame */
269 CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
270 CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
272 /* Push a clean set of CPU registers for asm_switch_context() */
273 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
274 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
276 /* Add to ready list */
277 ATOMIC(SCHED_ENQUEUE(proc));
279 #if CONFIG_KERN_MONITOR
280 monitor_add(proc, name, stack_base, stacksize);
286 /*! Rename a process */
287 void proc_rename(struct Process *proc, const char *name)
289 #if CONFIG_KERN_MONITOR
290 monitor_rename(proc, name);
292 (void)proc; (void)name;
298 * System scheduler: pass CPU control to the next process in
301 * Saving and restoring the context on the stack is done
302 * by a CPU-dependent support routine which must usually be
303 * written in assembly.
305 void proc_schedule(void)
307 /* This function must not have any "auto" variables, otherwise
308 * the compiler might put them on the stack of the process
309 * being switched out.
311 static struct Process *old_process;
312 static cpuflags_t flags;
314 /* Remember old process to save its context later */
315 old_process = CurrentProcess;
318 /* Scheduling in interrupts is a nono. */
319 ASSERT(!IRQ_RUNNING());
322 /* Poll on the ready queue for the first ready process */
323 IRQ_SAVE_DISABLE(flags);
324 while (!(CurrentProcess = (struct Process *)list_remHead(&ProcReadyList)))
327 * Make sure we physically reenable interrupts here, no matter what
328 * the current task status is. This is important because if we
329 * are idle-spinning, we must allow interrupts, otherwise no
330 * process will ever wake up.
332 * \todo If there was a way to write sig_wait() so that it does not
333 * disable interrupts while waiting, there would not be any
343 * Optimization: don't switch contexts when the active
344 * process has not changed.
346 if (CurrentProcess != old_process)
348 static cpustack_t *dummy;
350 #if CONFIG_KERN_PREEMPTIVE
351 /* Reset quantum for this process */
352 Quantum = CONFIG_KERN_QUANTUM;
355 /* Save context of old process and switch to new process. If there is no
356 * old process, we save the old stack pointer into a dummy variable that
357 * we ignore. In fact, this happens only when the old process has just
359 * TODO: Instead of physically clearing the process at exit time, a zombie
360 * list should be created.
362 asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
365 /* This RET resumes the execution on the new process */
370 * Terminate the current process
374 #if CONFIG_KERN_MONITOR
375 monitor_remove(CurrentProcess);
380 * The following code is BROKEN.
381 * We are freeing our own stack before entering proc_schedule()
382 * BAJO: A correct fix would be to rearrange the scheduler with
383 * an additional parameter which frees the old stack/process
384 * after a context switch.
386 if (CurrentProcess->flags & PF_FREESTACK)
387 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
388 heap_free(CurrentProcess);
391 #if (ARCH & ARCH_EMUL)
392 #warning This is wrong
393 /* Reinsert process stack in free list */
394 ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
395 - (CONFIG_KERN_DEFSTACKSIZE / sizeof(cpustack_t))));
398 * NOTE: At this point the first two words of what used
399 * to be our stack contain a list node. From now on, we
400 * rely on the compiler not reading/writing the stack.
402 #endif /* ARCH_EMUL */
404 CurrentProcess = NULL;
411 * Co-operative context switch
413 void proc_switch(void)
415 /* Just like proc_schedule, this function must not have auto variables. */
416 static cpuflags_t flags;
418 IRQ_SAVE_DISABLE(flags);
419 SCHED_ENQUEUE(CurrentProcess);
427 * Get the pointer to the current process
429 struct Process *proc_current(void)
431 return CurrentProcess;
435 * Get the pointer to the user data of the current process
437 iptr_t proc_current_user_data(void)
439 return CurrentProcess->user_data;
443 #if CONFIG_KERN_PREEMPTIVE
446 * Disable preemptive task switching.
448 * The scheduler maintains a per-process nesting counter. Task switching is
449 * effectively re-enabled only when the number of calls to proc_permit()
450 * matches the number of calls to proc_forbid().
452 * Calling functions that could sleep while task switching is disabled
453 * is dangerous, although supported. Preemptive task switching is
454 * resumed while the process is sleeping and disabled again as soon as
459 void proc_forbid(void)
461 /* No need to protect against interrupts here. */
462 ++CurrentProcess->forbid_cnt;
466 * Re-enable preemptive task switching.
470 void proc_permit(void)
472 /* No need to protect against interrupts here. */
473 --CurrentProcess->forbid_cnt;
476 #endif /* CONFIG_KERN_PREEMPTIVE */
479 #if 0 /* Simple testcase for the scheduler */
481 #include <drv/timer.h>
484 * Proc scheduling test subthread 1
486 static void NORETURN proc_test_thread1(void)
497 * Proc scheduling test subthread 2
499 static void NORETURN proc_test_thread2(void)
509 static cpustack_t proc_test_stack1[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
510 static cpustack_t proc_test_stack2[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
513 * Proc scheduling test
515 void NORETURN proc_test(void)
517 proc_new(proc_test_thread1, NULL, sizeof(proc_test_stack1), proc_test_stack1);
518 proc_new(proc_test_thread2, NULL, sizeof(proc_test_stack2), proc_test_stack2);
519 kputs("Created tasks\n");
522 kdump(proc_test_stack1+sizeof(proc_test_stack1)-64, 64);
524 kdump(proc_test_stack2+sizeof(proc_test_stack1)-64, 64);
528 kputs(">main task\n");