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 1.17 2004/10/19 08:47:13 bernie
21 *#* proc_rename(), proc_forbid(), proc_permit(): New functions.
23 *#* Revision 1.16 2004/10/03 20:39:28 bernie
24 *#* Import changes from sc/firmware.
26 *#* Revision 1.15 2004/09/20 03:29:39 bernie
29 *#* Revision 1.14 2004/09/14 21:06:44 bernie
30 *#* Use debug.h instead of kdebug.h.
32 *#* Revision 1.13 2004/08/29 21:58:53 bernie
33 *#* Include macros.h explicityl.
35 *#* Revision 1.11 2004/08/24 16:09:08 bernie
36 *#* Add missing header.
38 *#* Revision 1.10 2004/08/24 16:07:01 bernie
39 *#* Use kputs()/kputchar() when possible.
41 *#* Revision 1.9 2004/08/24 14:26:57 bernie
42 *#* monitor_debug_stacks(): Conditionally compile on CONFIG_KERN_MONITOR.
44 *#* Revision 1.8 2004/08/14 19:37:57 rasky
45 *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
47 *#* Revision 1.7 2004/08/02 20:20:29 aleph
48 *#* Merge from project_ks
50 *#* Revision 1.6 2004/07/30 14:24:16 rasky
51 *#* Task switching con salvataggio perfetto stato di interrupt (SR)
52 *#* Kernel monitor per dump informazioni su stack dei processi
54 *#* Revision 1.5 2004/07/14 14:18:09 rasky
55 *#* Merge da SC: Rimosso timer dentro il task, che รจ uno spreco di memoria per troppi task
57 *#* Revision 1.4 2004/07/13 19:21:28 aleph
58 *#* Avoid warning for unused arg when compiled without some CONFIG_KERN_xx options
60 *#* Revision 1.3 2004/06/06 18:37:57 bernie
61 *#* Rename event macros to look like regular functions.
63 *#* Revision 1.2 2004/06/03 11:27:09 bernie
64 *#* Add dual-license information.
66 *#* Revision 1.1 2004/05/23 17:27:00 bernie
67 *#* Import kern/ subdirectory.
77 #include <arch_config.h> /* ARCH_EMUL */
78 #include <macros.h> /* ABS() */
80 #include <string.h> /* memset() */
83 * CPU dependent context switching routines.
85 * \note This function *MUST* preserve also the status of the interrupts.
87 EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
88 EXTERN_C int asm_switch_version(void);
91 * The scheduer tracks ready and waiting processes
92 * by enqueuing them in these lists. A pointer to the currently
93 * running process is stored in the CurrentProcess pointer.
95 * NOTE: these variables are protected by DI/EI locking
97 REGISTER Process *CurrentProcess;
98 REGISTER List ProcReadyList;
101 #if CONFIG_KERN_PREEMPTIVE
103 * The time sharing scheduler forces a task switch when
104 * the current process has consumed its quantum.
110 /* In Win32 we must emulate stack on the real process stack */
111 #if (ARCH & ARCH_EMUL)
112 extern List StackFreeList;
115 /* The main process (the one that executes main()) */
116 struct Process MainProcess;
119 static void proc_init_struct(Process* proc)
121 /* Avoid warning for unused argument */
124 #if CONFIG_KERN_SIGNALS
136 INITLIST(&ProcReadyList);
138 #if CONFIG_KERN_MONITOR
142 /* We "promote" the current context into a real process. The only thing we have
143 * to do is create a PCB and make it current. We don't need to setup the stack
144 * pointer because it will be written the first time we switch to another process.
146 proc_init_struct(&MainProcess);
147 CurrentProcess = &MainProcess;
149 /* Make sure the assembly routine is up-to-date with us */
150 ASSERT(asm_switch_version() == 1);
155 * Create a new process, starting at the provided entry point.
157 * \return Process structure of new created process
158 * if successful, NULL otherwise.
160 struct Process *proc_new_with_name(UNUSED(const char*, name), void (*entry)(void), IPTR data, size_t stacksize, cpustack_t *stack_base)
165 size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
167 bool free_stack = false;
170 #if (ARCH & ARCH_EMUL)
171 /* Ignore stack provided by caller
172 * and use the large enough default instead
174 stack_base = (cpustack_t *)StackFreeList.head;
175 REMOVE((Node *)stack_base);
176 stacksize = DEF_STACKSIZE;
177 #elif CONFIG_KERN_HEAP
178 /* Did the caller provide a stack for us? */
181 /* Did the caller specify the desired stack size? */
183 stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
185 /* Allocate stack dinamically */
186 if (!(stack_base = heap_alloc(stacksize)))
192 /* Stack must have been provided by the user */
197 #if CONFIG_KERN_MONITOR
198 /* Fill-in the stack with a special marker to help debugging */
199 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
202 /* Initialize the process control block */
203 if (CPU_STACK_GROWS_UPWARD)
205 proc = (Process*)stack_base;
206 proc->stack = stack_base + proc_size_words;
207 if (CPU_SP_ON_EMPTY_SLOT)
212 proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
213 proc->stack = (cpustack_t*)proc;
214 if (CPU_SP_ON_EMPTY_SLOT)
218 proc_init_struct(proc);
219 proc->user_data = data;
222 proc->stack_base = stack_base;
223 proc->stack_size = stack_size;
225 proc->flags |= PF_FREESTACK;
228 /* Initialize process stack frame */
229 CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
230 CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
232 /* Push a clean set of CPU registers for asm_switch_context() */
233 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
234 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
236 /* Add to ready list */
237 DISABLE_IRQSAVE(flags);
239 ENABLE_IRQRESTORE(flags);
241 #if CONFIG_KERN_MONITOR
242 monitor_add(proc, name, stack_base, stacksize);
248 /*! Rename a process */
249 void proc_rename(struct Process *proc, const char *name)
251 #if CONFIG_KERN_MONITOR
252 monitor_rename(proc, name);
258 * System scheduler: pass CPU control to the next process in
261 * Saving and restoring the context on the stack is done
262 * by a CPU-dependent support routine which must usually be
263 * written in assembly.
265 void proc_schedule(void)
267 /* This function must not have any "auto" variables, otherwise
268 * the compiler might put them on the stack of the process
269 * being switched out.
271 static Process *old_process;
272 static cpuflags_t flags;
274 /* Remember old process to save its context later */
275 old_process = CurrentProcess;
277 /* Poll on the ready queue for the first ready process */
278 DISABLE_IRQSAVE(flags);
279 while (!(CurrentProcess = (struct Process*)REMHEAD(&ProcReadyList)))
282 * Make sure we physically reenable interrupts here, no matter what
283 * the current task status is. This is important because if we
284 * are idle-spinning, we must allow interrupts, otherwise no
285 * process will ever wake up.
287 * \todo If there was a way to code sig_wait so that it does not
288 * disable interrupts while waiting, there would not be any
295 ENABLE_IRQRESTORE(flags);
297 /* Optimization: don't switch contexts when the active
298 * process has not changed.
300 if (CurrentProcess != old_process)
302 static cpustack_t* dummy;
304 #if CONFIG_KERN_PREEMPTIVE
305 /* Reset quantum for this process */
306 Quantum = CONFIG_KERN_QUANTUM;
309 /* Save context of old process and switch to new process. If there is no
310 * old process, we save the old stack pointer into a dummy variable that
311 * we ignore. In fact, this happens only when the old process has just
313 * TODO: Instead of physically clearing the process at exit time, a zombie
314 * list should be created.
316 asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
319 /* This RET resumes the execution on the new process */
324 * Terminate the current process
329 /* The following code is BROKEN.
330 * We are freeing our own stack before entering proc_schedule()
331 * BAJO: A correct fix would be to rearrange the scheduler with
332 * an additional parameter which frees the old stack/process
333 * after a context switch.
335 if (CurrentProcess->flags & PF_FREESTACK)
336 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
337 heap_free(CurrentProcess);
340 #if (ARCH & ARCH_EMUL)
342 /* Reinsert process stack in free list */
343 ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
344 - (DEF_STACKSIZE / sizeof(cpustack_t))));
346 /* NOTE: At this point the first two words of what used
347 * to be our stack contain a list node. From now on, we
348 * rely on the compiler not reading/writing the stack.
350 #endif /* ARCH_EMUL */
352 #if CONFIG_KERN_MONITOR
353 monitor_remove(CurrentProcess);
356 CurrentProcess = NULL;
363 * Co-operative context switch
365 void proc_switch(void)
367 /* Just like proc_schedule, this function must not have auto variables. */
368 static cpuflags_t flags;
370 DISABLE_IRQSAVE(flags);
371 SCHED_ENQUEUE(CurrentProcess);
372 ENABLE_IRQRESTORE(flags);
379 * Get the pointer to the current process
381 struct Process *proc_current(void)
383 return CurrentProcess;
387 * Get the pointer to the user data of the current process
389 IPTR proc_current_user_data(void)
391 return CurrentProcess->user_data;
395 #if CONFIG_KERN_PREEMPTIVE
398 * Disable preemptive task switching.
400 * The scheduler maintains a per-process nesting counter. Task switching is
401 * effectively re-enabled only when the number of calls to proc_permit()
402 * matches the number of calls to proc_forbid().
404 * Calling functions that could sleep while task switching is disabled
405 * is dangerous, although supported. Preemptive task switching is
406 * resumed while the process is sleeping and disabled again as soon as
411 void proc_forbid(void)
413 /* No need to protect against interrupts here. */
414 ++CurrentProcess->forbid_cnt;
418 * Re-enable preemptive task switching.
422 void proc_permit(void)
424 /* No need to protect against interrupts here. */
425 --CurrentProcess->forbid_cnt;
429 #if 0 /* Simple testcase for the scheduler */
431 #include <drv/timer.h>
434 * Proc scheduling test subthread 1
436 static void NORETURN proc_test_thread1(void)
447 * Proc scheduling test subthread 2
449 static void NORETURN proc_test_thread2(void)
459 static cpustack_t proc_test_stack1[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
460 static cpustack_t proc_test_stack2[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
463 * Proc scheduling test
465 void NORETURN proc_test(void)
467 proc_new(proc_test_thread1, NULL, sizeof(proc_test_stack1), proc_test_stack1);
468 proc_new(proc_test_thread2, NULL, sizeof(proc_test_stack2), proc_test_stack2);
469 kputs("Created tasks\n");
472 kdump(proc_test_stack1+sizeof(proc_test_stack1)-64, 64);
474 kdump(proc_test_stack2+sizeof(proc_test_stack1)-64, 64);
478 kputs(">main task\n");