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 1.24 2005/01/08 09:20:54 bernie
21 *#* Remove unused variable.
23 *#* Revision 1.23 2004/12/13 12:07:06 bernie
24 *#* DISABLE_IRQSAVE/ENABLE_IRQRESTORE: Convert to IRQ_SAVE_DISABLE/IRQ_RESTORE.
26 *#* Revision 1.22 2004/12/13 11:51:08 bernie
27 *#* DISABLE_INTS/ENABLE_INTS: Convert to IRQ_DISABLE/IRQ_ENABLE.
29 *#* Revision 1.21 2004/11/28 23:20:25 bernie
30 *#* Remove obsolete INITLIST macro.
32 *#* Revision 1.20 2004/11/16 22:37:14 bernie
33 *#* Replace IPTR with iptr_t.
35 *#* Revision 1.19 2004/10/19 11:47:39 bernie
36 *#* Kill warnings when !CONFIG_PROC_MONITOR.
38 *#* Revision 1.18 2004/10/19 08:54:43 bernie
39 *#* Initialize forbid_cnt; Formatting/comments fixes.
41 *#* Revision 1.17 2004/10/19 08:47:13 bernie
42 *#* proc_rename(), proc_forbid(), proc_permit(): New functions.
44 *#* Revision 1.16 2004/10/03 20:39:28 bernie
45 *#* Import changes from sc/firmware.
47 *#* Revision 1.15 2004/09/20 03:29:39 bernie
50 *#* Revision 1.14 2004/09/14 21:06:44 bernie
51 *#* Use debug.h instead of kdebug.h.
53 *#* Revision 1.13 2004/08/29 21:58:53 bernie
54 *#* Include macros.h explicityl.
56 *#* Revision 1.11 2004/08/24 16:09:08 bernie
57 *#* Add missing header.
59 *#* Revision 1.10 2004/08/24 16:07:01 bernie
60 *#* Use kputs()/kputchar() when possible.
62 *#* Revision 1.9 2004/08/24 14:26:57 bernie
63 *#* monitor_debug_stacks(): Conditionally compile on CONFIG_KERN_MONITOR.
65 *#* Revision 1.8 2004/08/14 19:37:57 rasky
66 *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
68 *#* Revision 1.7 2004/08/02 20:20:29 aleph
69 *#* Merge from project_ks
71 *#* Revision 1.6 2004/07/30 14:24:16 rasky
72 *#* Task switching con salvataggio perfetto stato di interrupt (SR)
73 *#* Kernel monitor per dump informazioni su stack dei processi
75 *#* Revision 1.5 2004/07/14 14:18:09 rasky
76 *#* Merge da SC: Rimosso timer dentro il task, che รจ uno spreco di memoria per troppi task
78 *#* Revision 1.4 2004/07/13 19:21:28 aleph
79 *#* Avoid warning for unused arg when compiled without some CONFIG_KERN_xx options
81 *#* Revision 1.3 2004/06/06 18:37:57 bernie
82 *#* Rename event macros to look like regular functions.
84 *#* Revision 1.2 2004/06/03 11:27:09 bernie
85 *#* Add dual-license information.
87 *#* Revision 1.1 2004/05/23 17:27:00 bernie
88 *#* Import kern/ subdirectory.
98 #include <arch_config.h> /* ARCH_EMUL */
99 #include <macros.h> /* ABS() */
101 #include <string.h> /* memset() */
104 * CPU dependent context switching routines.
106 * \note This function *MUST* preserve also the status of the interrupts.
108 EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
109 EXTERN_C int asm_switch_version(void);
112 * The scheduer tracks ready and waiting processes
113 * by enqueuing them in these lists. A pointer to the currently
114 * running process is stored in the CurrentProcess pointer.
116 * NOTE: these variables are protected by DI/EI locking
118 REGISTER Process *CurrentProcess;
119 REGISTER List ProcReadyList;
122 #if CONFIG_KERN_PREEMPTIVE
124 * The time sharing scheduler forces a task switch when
125 * the current process has consumed its quantum.
131 /* In Win32 we must emulate stack on the real process stack */
132 #if (ARCH & ARCH_EMUL)
133 extern List StackFreeList;
136 /*! The main process (the one that executes main()). */
137 struct Process MainProcess;
140 static void proc_init_struct(Process *proc)
142 /* Avoid warning for unused argument. */
145 #if CONFIG_KERN_SIGNALS
149 #if CONFIG_KERN_PREEMPTIVE
150 proc->forbid_cnt = 0;
161 LIST_INIT(&ProcReadyList);
163 #if CONFIG_KERN_MONITOR
167 /* We "promote" the current context into a real process. The only thing we have
168 * to do is create a PCB and make it current. We don't need to setup the stack
169 * pointer because it will be written the first time we switch to another process.
171 proc_init_struct(&MainProcess);
172 CurrentProcess = &MainProcess;
174 /* Make sure the assembly routine is up-to-date with us */
175 ASSERT(asm_switch_version() == 1);
180 * Create a new process, starting at the provided entry point.
182 * \return Process structure of new created process
183 * if successful, NULL otherwise.
185 struct Process *proc_new_with_name(UNUSED(const char*, name), void (*entry)(void), iptr_t data, size_t stacksize, cpustack_t *stack_base)
189 size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
191 bool free_stack = false;
194 #if (ARCH & ARCH_EMUL)
195 /* Ignore stack provided by caller and use the large enough default instead. */
196 stack_base = (cpustack_t *)StackFreeList.head;
197 REMOVE((Node *)stack_base);
198 stacksize = DEF_STACKSIZE;
199 #elif CONFIG_KERN_HEAP
200 /* Did the caller provide a stack for us? */
203 /* Did the caller specify the desired stack size? */
205 stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
207 /* Allocate stack dinamically */
208 if (!(stack_base = heap_alloc(stacksize)))
214 /* Stack must have been provided by the user */
219 #if CONFIG_KERN_MONITOR
220 /* Fill-in the stack with a special marker to help debugging */
221 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
224 /* Initialize the process control block */
225 if (CPU_STACK_GROWS_UPWARD)
227 proc = (Process*)stack_base;
228 proc->stack = stack_base + proc_size_words;
229 if (CPU_SP_ON_EMPTY_SLOT)
234 proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
235 proc->stack = (cpustack_t*)proc;
236 if (CPU_SP_ON_EMPTY_SLOT)
240 proc_init_struct(proc);
241 proc->user_data = data;
244 proc->stack_base = stack_base;
245 proc->stack_size = stack_size;
247 proc->flags |= PF_FREESTACK;
250 /* Initialize process stack frame */
251 CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
252 CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
254 /* Push a clean set of CPU registers for asm_switch_context() */
255 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
256 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
258 /* Add to ready list */
259 ATOMIC(SCHED_ENQUEUE(proc));
261 #if CONFIG_KERN_MONITOR
262 monitor_add(proc, name, stack_base, stacksize);
268 /*! Rename a process */
269 void proc_rename(struct Process *proc, const char *name)
271 #if CONFIG_KERN_MONITOR
272 monitor_rename(proc, name);
274 (void)proc; (void)name;
280 * System scheduler: pass CPU control to the next process in
283 * Saving and restoring the context on the stack is done
284 * by a CPU-dependent support routine which must usually be
285 * written in assembly.
287 void proc_schedule(void)
289 /* This function must not have any "auto" variables, otherwise
290 * the compiler might put them on the stack of the process
291 * being switched out.
293 static struct Process *old_process;
294 static cpuflags_t flags;
296 /* Remember old process to save its context later */
297 old_process = CurrentProcess;
299 /* Poll on the ready queue for the first ready process */
300 IRQ_SAVE_DISABLE(flags);
301 while (!(CurrentProcess = (struct Process *)REMHEAD(&ProcReadyList)))
304 * Make sure we physically reenable interrupts here, no matter what
305 * the current task status is. This is important because if we
306 * are idle-spinning, we must allow interrupts, otherwise no
307 * process will ever wake up.
309 * \todo If there was a way to write sig_wait() so that it does not
310 * disable interrupts while waiting, there would not be any
320 * Optimization: don't switch contexts when the active
321 * process has not changed.
323 if (CurrentProcess != old_process)
325 static cpustack_t *dummy;
327 #if CONFIG_KERN_PREEMPTIVE
328 /* Reset quantum for this process */
329 Quantum = CONFIG_KERN_QUANTUM;
332 /* Save context of old process and switch to new process. If there is no
333 * old process, we save the old stack pointer into a dummy variable that
334 * we ignore. In fact, this happens only when the old process has just
336 * TODO: Instead of physically clearing the process at exit time, a zombie
337 * list should be created.
339 asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
342 /* This RET resumes the execution on the new process */
347 * Terminate the current process
352 /* The following code is BROKEN.
353 * We are freeing our own stack before entering proc_schedule()
354 * BAJO: A correct fix would be to rearrange the scheduler with
355 * an additional parameter which frees the old stack/process
356 * after a context switch.
358 if (CurrentProcess->flags & PF_FREESTACK)
359 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
360 heap_free(CurrentProcess);
363 #if (ARCH & ARCH_EMUL)
365 /* Reinsert process stack in free list */
366 ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
367 - (DEF_STACKSIZE / sizeof(cpustack_t))));
369 /* NOTE: At this point the first two words of what used
370 * to be our stack contain a list node. From now on, we
371 * rely on the compiler not reading/writing the stack.
373 #endif /* ARCH_EMUL */
375 #if CONFIG_KERN_MONITOR
376 monitor_remove(CurrentProcess);
379 CurrentProcess = NULL;
386 * Co-operative context switch
388 void proc_switch(void)
390 /* Just like proc_schedule, this function must not have auto variables. */
391 static cpuflags_t flags;
393 IRQ_SAVE_DISABLE(flags);
394 SCHED_ENQUEUE(CurrentProcess);
402 * Get the pointer to the current process
404 struct Process *proc_current(void)
406 return CurrentProcess;
410 * Get the pointer to the user data of the current process
412 iptr_t proc_current_user_data(void)
414 return CurrentProcess->user_data;
418 #if CONFIG_KERN_PREEMPTIVE
421 * Disable preemptive task switching.
423 * The scheduler maintains a per-process nesting counter. Task switching is
424 * effectively re-enabled only when the number of calls to proc_permit()
425 * matches the number of calls to proc_forbid().
427 * Calling functions that could sleep while task switching is disabled
428 * is dangerous, although supported. Preemptive task switching is
429 * resumed while the process is sleeping and disabled again as soon as
434 void proc_forbid(void)
436 /* No need to protect against interrupts here. */
437 ++CurrentProcess->forbid_cnt;
441 * Re-enable preemptive task switching.
445 void proc_permit(void)
447 /* No need to protect against interrupts here. */
448 --CurrentProcess->forbid_cnt;
451 #endif /* CONFIG_KERN_PREEMPTIVE */
454 #if 0 /* Simple testcase for the scheduler */
456 #include <drv/timer.h>
459 * Proc scheduling test subthread 1
461 static void NORETURN proc_test_thread1(void)
472 * Proc scheduling test subthread 2
474 static void NORETURN proc_test_thread2(void)
484 static cpustack_t proc_test_stack1[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
485 static cpustack_t proc_test_stack2[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
488 * Proc scheduling test
490 void NORETURN proc_test(void)
492 proc_new(proc_test_thread1, NULL, sizeof(proc_test_stack1), proc_test_stack1);
493 proc_new(proc_test_thread2, NULL, sizeof(proc_test_stack2), proc_test_stack2);
494 kputs("Created tasks\n");
497 kdump(proc_test_stack1+sizeof(proc_test_stack1)-64, 64);
499 kdump(proc_test_stack2+sizeof(proc_test_stack1)-64, 64);
503 kputs(">main task\n");