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 1.27 2005/11/04 16:20:02 bernie
21 *#* Fix reference to README.devlib in header.
23 *#* Revision 1.26 2005/04/11 19:10:28 bernie
24 *#* Include top-level headers from cfg/ subdir.
26 *#* Revision 1.25 2005/03/15 00:20:54 bernie
27 *#* proc_schedule(): New sanity check.
29 *#* Revision 1.24 2005/01/08 09:20:54 bernie
30 *#* Remove unused variable.
32 *#* Revision 1.23 2004/12/13 12:07:06 bernie
33 *#* DISABLE_IRQSAVE/ENABLE_IRQRESTORE: Convert to IRQ_SAVE_DISABLE/IRQ_RESTORE.
35 *#* Revision 1.22 2004/12/13 11:51:08 bernie
36 *#* DISABLE_INTS/ENABLE_INTS: Convert to IRQ_DISABLE/IRQ_ENABLE.
38 *#* Revision 1.21 2004/11/28 23:20:25 bernie
39 *#* Remove obsolete INITLIST macro.
41 *#* Revision 1.20 2004/11/16 22:37:14 bernie
42 *#* Replace IPTR with iptr_t.
44 *#* Revision 1.19 2004/10/19 11:47:39 bernie
45 *#* Kill warnings when !CONFIG_PROC_MONITOR.
47 *#* Revision 1.18 2004/10/19 08:54:43 bernie
48 *#* Initialize forbid_cnt; Formatting/comments fixes.
50 *#* Revision 1.17 2004/10/19 08:47:13 bernie
51 *#* proc_rename(), proc_forbid(), proc_permit(): New functions.
53 *#* Revision 1.16 2004/10/03 20:39:28 bernie
54 *#* Import changes from sc/firmware.
56 *#* Revision 1.15 2004/09/20 03:29:39 bernie
59 *#* Revision 1.14 2004/09/14 21:06:44 bernie
60 *#* Use debug.h instead of kdebug.h.
62 *#* Revision 1.13 2004/08/29 21:58:53 bernie
63 *#* Include macros.h explicityl.
65 *#* Revision 1.11 2004/08/24 16:09:08 bernie
66 *#* Add missing header.
68 *#* Revision 1.10 2004/08/24 16:07:01 bernie
69 *#* Use kputs()/kputchar() when possible.
71 *#* Revision 1.9 2004/08/24 14:26:57 bernie
72 *#* monitor_debug_stacks(): Conditionally compile on CONFIG_KERN_MONITOR.
74 *#* Revision 1.8 2004/08/14 19:37:57 rasky
75 *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc.
77 *#* Revision 1.7 2004/08/02 20:20:29 aleph
78 *#* Merge from project_ks
80 *#* Revision 1.6 2004/07/30 14:24:16 rasky
81 *#* Task switching con salvataggio perfetto stato di interrupt (SR)
82 *#* Kernel monitor per dump informazioni su stack dei processi
84 *#* Revision 1.5 2004/07/14 14:18:09 rasky
85 *#* Merge da SC: Rimosso timer dentro il task, che รจ uno spreco di memoria per troppi task
87 *#* Revision 1.4 2004/07/13 19:21:28 aleph
88 *#* Avoid warning for unused arg when compiled without some CONFIG_KERN_xx options
90 *#* Revision 1.3 2004/06/06 18:37:57 bernie
91 *#* Rename event macros to look like regular functions.
93 *#* Revision 1.2 2004/06/03 11:27:09 bernie
94 *#* Add dual-license information.
96 *#* Revision 1.1 2004/05/23 17:27:00 bernie
97 *#* Import kern/ subdirectory.
106 #include <cfg/debug.h>
107 #include <cfg/arch_config.h> /* ARCH_EMUL */
108 #include <cfg/macros.h> /* ABS() */
110 #include <string.h> /* memset() */
113 * CPU dependent context switching routines.
115 * \note This function *MUST* preserve also the status of the interrupts.
117 EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
118 EXTERN_C int asm_switch_version(void);
121 * The scheduer tracks ready and waiting processes
122 * by enqueuing them in these lists. A pointer to the currently
123 * running process is stored in the CurrentProcess pointer.
125 * NOTE: these variables are protected by DI/EI locking
127 REGISTER Process *CurrentProcess;
128 REGISTER List ProcReadyList;
131 #if CONFIG_KERN_PREEMPTIVE
133 * The time sharing scheduler forces a task switch when
134 * the current process has consumed its quantum.
140 /* In Win32 we must emulate stack on the real process stack */
141 #if (ARCH & ARCH_EMUL)
142 extern List StackFreeList;
145 /*! The main process (the one that executes main()). */
146 struct Process MainProcess;
149 static void proc_init_struct(Process *proc)
151 /* Avoid warning for unused argument. */
154 #if CONFIG_KERN_SIGNALS
158 #if CONFIG_KERN_PREEMPTIVE
159 proc->forbid_cnt = 0;
170 LIST_INIT(&ProcReadyList);
172 #if CONFIG_KERN_MONITOR
176 /* We "promote" the current context into a real process. The only thing we have
177 * to do is create a PCB and make it current. We don't need to setup the stack
178 * pointer because it will be written the first time we switch to another process.
180 proc_init_struct(&MainProcess);
181 CurrentProcess = &MainProcess;
183 /* Make sure the assembly routine is up-to-date with us */
184 ASSERT(asm_switch_version() == 1);
189 * Create a new process, starting at the provided entry point.
191 * \return Process structure of new created process
192 * if successful, NULL otherwise.
194 struct Process *proc_new_with_name(UNUSED(const char*, name), void (*entry)(void), iptr_t data, size_t stacksize, cpustack_t *stack_base)
198 size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
200 bool free_stack = false;
203 #if (ARCH & ARCH_EMUL)
204 /* Ignore stack provided by caller and use the large enough default instead. */
205 stack_base = (cpustack_t *)StackFreeList.head;
206 REMOVE((Node *)stack_base);
207 stacksize = DEF_STACKSIZE;
208 #elif CONFIG_KERN_HEAP
209 /* Did the caller provide a stack for us? */
212 /* Did the caller specify the desired stack size? */
214 stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
216 /* Allocate stack dinamically */
217 if (!(stack_base = heap_alloc(stacksize)))
223 /* Stack must have been provided by the user */
228 #if CONFIG_KERN_MONITOR
229 /* Fill-in the stack with a special marker to help debugging */
230 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
233 /* Initialize the process control block */
234 if (CPU_STACK_GROWS_UPWARD)
236 proc = (Process*)stack_base;
237 proc->stack = stack_base + proc_size_words;
238 if (CPU_SP_ON_EMPTY_SLOT)
243 proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
244 proc->stack = (cpustack_t*)proc;
245 if (CPU_SP_ON_EMPTY_SLOT)
249 proc_init_struct(proc);
250 proc->user_data = data;
253 proc->stack_base = stack_base;
254 proc->stack_size = stack_size;
256 proc->flags |= PF_FREESTACK;
259 /* Initialize process stack frame */
260 CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
261 CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
263 /* Push a clean set of CPU registers for asm_switch_context() */
264 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
265 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
267 /* Add to ready list */
268 ATOMIC(SCHED_ENQUEUE(proc));
270 #if CONFIG_KERN_MONITOR
271 monitor_add(proc, name, stack_base, stacksize);
277 /*! Rename a process */
278 void proc_rename(struct Process *proc, const char *name)
280 #if CONFIG_KERN_MONITOR
281 monitor_rename(proc, name);
283 (void)proc; (void)name;
289 * System scheduler: pass CPU control to the next process in
292 * Saving and restoring the context on the stack is done
293 * by a CPU-dependent support routine which must usually be
294 * written in assembly.
296 void proc_schedule(void)
298 /* This function must not have any "auto" variables, otherwise
299 * the compiler might put them on the stack of the process
300 * being switched out.
302 static struct Process *old_process;
303 static cpuflags_t flags;
305 /* Remember old process to save its context later */
306 old_process = CurrentProcess;
308 /* Scheduling in interrupts is a nono. */
309 ASSERT(!IRQ_RUNNING());
311 /* Poll on the ready queue for the first ready process */
312 IRQ_SAVE_DISABLE(flags);
313 while (!(CurrentProcess = (struct Process *)REMHEAD(&ProcReadyList)))
316 * Make sure we physically reenable interrupts here, no matter what
317 * the current task status is. This is important because if we
318 * are idle-spinning, we must allow interrupts, otherwise no
319 * process will ever wake up.
321 * \todo If there was a way to write sig_wait() so that it does not
322 * disable interrupts while waiting, there would not be any
332 * Optimization: don't switch contexts when the active
333 * process has not changed.
335 if (CurrentProcess != old_process)
337 static cpustack_t *dummy;
339 #if CONFIG_KERN_PREEMPTIVE
340 /* Reset quantum for this process */
341 Quantum = CONFIG_KERN_QUANTUM;
344 /* Save context of old process and switch to new process. If there is no
345 * old process, we save the old stack pointer into a dummy variable that
346 * we ignore. In fact, this happens only when the old process has just
348 * TODO: Instead of physically clearing the process at exit time, a zombie
349 * list should be created.
351 asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
354 /* This RET resumes the execution on the new process */
359 * Terminate the current process
364 /* The following code is BROKEN.
365 * We are freeing our own stack before entering proc_schedule()
366 * BAJO: A correct fix would be to rearrange the scheduler with
367 * an additional parameter which frees the old stack/process
368 * after a context switch.
370 if (CurrentProcess->flags & PF_FREESTACK)
371 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
372 heap_free(CurrentProcess);
375 #if (ARCH & ARCH_EMUL)
377 /* Reinsert process stack in free list */
378 ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
379 - (DEF_STACKSIZE / sizeof(cpustack_t))));
381 /* NOTE: At this point the first two words of what used
382 * to be our stack contain a list node. From now on, we
383 * rely on the compiler not reading/writing the stack.
385 #endif /* ARCH_EMUL */
387 #if CONFIG_KERN_MONITOR
388 monitor_remove(CurrentProcess);
391 CurrentProcess = NULL;
398 * Co-operative context switch
400 void proc_switch(void)
402 /* Just like proc_schedule, this function must not have auto variables. */
403 static cpuflags_t flags;
405 IRQ_SAVE_DISABLE(flags);
406 SCHED_ENQUEUE(CurrentProcess);
414 * Get the pointer to the current process
416 struct Process *proc_current(void)
418 return CurrentProcess;
422 * Get the pointer to the user data of the current process
424 iptr_t proc_current_user_data(void)
426 return CurrentProcess->user_data;
430 #if CONFIG_KERN_PREEMPTIVE
433 * Disable preemptive task switching.
435 * The scheduler maintains a per-process nesting counter. Task switching is
436 * effectively re-enabled only when the number of calls to proc_permit()
437 * matches the number of calls to proc_forbid().
439 * Calling functions that could sleep while task switching is disabled
440 * is dangerous, although supported. Preemptive task switching is
441 * resumed while the process is sleeping and disabled again as soon as
446 void proc_forbid(void)
448 /* No need to protect against interrupts here. */
449 ++CurrentProcess->forbid_cnt;
453 * Re-enable preemptive task switching.
457 void proc_permit(void)
459 /* No need to protect against interrupts here. */
460 --CurrentProcess->forbid_cnt;
463 #endif /* CONFIG_KERN_PREEMPTIVE */
466 #if 0 /* Simple testcase for the scheduler */
468 #include <drv/timer.h>
471 * Proc scheduling test subthread 1
473 static void NORETURN proc_test_thread1(void)
484 * Proc scheduling test subthread 2
486 static void NORETURN proc_test_thread2(void)
496 static cpustack_t proc_test_stack1[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
497 static cpustack_t proc_test_stack2[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
500 * Proc scheduling test
502 void NORETURN proc_test(void)
504 proc_new(proc_test_thread1, NULL, sizeof(proc_test_stack1), proc_test_stack1);
505 proc_new(proc_test_thread2, NULL, sizeof(proc_test_stack2), proc_test_stack2);
506 kputs("Created tasks\n");
509 kdump(proc_test_stack1+sizeof(proc_test_stack1)-64, 64);
511 kdump(proc_test_stack2+sizeof(proc_test_stack1)-64, 64);
515 kputs(">main task\n");