4 * This file is part of BeRTOS.
6 * Bertos is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
20 * As a special exception, you may use this file as part of a free software
21 * library without restriction. Specifically, if other files instantiate
22 * templates or use macros or inline functions from this file, or you compile
23 * this file and link it with other files to produce an executable, this
24 * file does not by itself cause the resulting executable to be covered by
25 * the GNU General Public License. This exception does not however
26 * invalidate any other reasons why the executable file might be covered by
27 * the GNU General Public License.
29 * Copyright 2001, 2004 Develer S.r.l. (http://www.develer.com/)
30 * Copyright 1999, 2000, 2001, 2008 Bernie Innocenti <bernie@codewiz.org>
33 * \brief Simple realtime multitasking scheduler.
34 * Context switching is only done cooperatively.
37 * \author Bernie Innocenti <bernie@codewiz.org>
38 * \author Stefano Fedrigo <aleph@develer.com>
44 #include "cfg/cfg_arch.h" /* ARCH_EMUL */
45 #include "cfg/cfg_kern.h"
46 #include <cfg/module.h>
47 #include <cfg/depend.h> // CONFIG_DEPEND()
50 #include <cpu/types.h>
52 #include <cpu/frame.h>
54 #include <string.h> /* memset() */
56 // Check config dependencies
57 CONFIG_DEPEND(CONFIG_KERN_SIGNALS, CONFIG_KERN_SCHED);
58 CONFIG_DEPEND(CONFIG_KERN_SEMAPHORES, CONFIG_KERN_SIGNALS);
59 CONFIG_DEPEND(CONFIG_KERN_MONITOR, CONFIG_KERN_SCHED);
63 * The scheduer tracks ready processes by enqueuing them in the
66 * \note Access to the list must occur while interrupts are disabled.
68 REGISTER List ProcReadyList;
71 * Holds a pointer to the TCB of the currently running process.
73 * \note User applications should use proc_current() to retrieve this value.
75 REGISTER Process *CurrentProcess;
77 #if (ARCH & ARCH_EMUL)
79 * In some hosted environments, we must emulate the stack on the real
80 * process stack to satisfy consistency checks in system libraries and
81 * because some ABIs place trampolines on the stack.
83 * Access to this list must be protected by PROC_ATOMIC().
88 cpustack_t proc_stacks[NPROC][(64 * 1024) / sizeof(cpustack_t)];
91 /** The main process (the one that executes main()). */
92 struct Process MainProcess;
95 static void proc_init_struct(Process *proc)
97 /* Avoid warning for unused argument. */
100 #if CONFIG_KERN_SIGNALS
117 LIST_INIT(&ProcReadyList);
120 LIST_INIT(&StackFreeList);
121 for (int i = 0; i < NPROC; i++)
122 ADDTAIL(&StackFreeList, (Node *)proc_stacks[i]);
126 * We "promote" the current context into a real process. The only thing we have
127 * to do is create a PCB and make it current. We don't need to setup the stack
128 * pointer because it will be written the first time we switch to another process.
130 proc_init_struct(&MainProcess);
131 CurrentProcess = &MainProcess;
133 #if CONFIG_KERN_MONITOR
135 monitor_add(CurrentProcess, "main");
138 #if CONFIG_KERN_PREEMPT
146 * Create a new process, starting at the provided entry point.
148 * \return Process structure of new created process
149 * if successful, NULL otherwise.
151 struct Process *proc_new_with_name(UNUSED(const char *, name), void (*entry)(void), iptr_t data, size_t stack_size, cpustack_t *stack_base)
154 const size_t PROC_SIZE_WORDS = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
156 bool free_stack = false;
158 TRACEMSG("name=%s", name);
160 #if (ARCH & ARCH_EMUL)
161 /* Ignore stack provided by caller and use the large enough default instead. */
162 PROC_ATOMIC(stack_base = (cpustack_t *)list_remHead(&StackFreeList));
164 stack_size = CONFIG_KERN_MINSTACKSIZE;
165 #elif CONFIG_KERN_HEAP
166 /* Did the caller provide a stack for us? */
169 /* Did the caller specify the desired stack size? */
171 stack_size = CONFIG_KERN_MINSTACKSIZE;
173 /* Allocate stack dinamically */
174 if (!(stack_base = heap_alloc(stack_size)))
180 #else // !ARCH_EMUL && !CONFIG_KERN_HEAP
182 /* Stack must have been provided by the user */
183 ASSERT_VALID_PTR(stack_base);
186 #endif // !ARCH_EMUL && !CONFIG_KERN_HEAP
188 #if CONFIG_KERN_MONITOR
189 /* Fill-in the stack with a special marker to help debugging */
190 memset(stack_base, CONFIG_KERN_STACKFILLCODE, stack_size);
193 /* Initialize the process control block */
194 if (CPU_STACK_GROWS_UPWARD)
196 proc = (Process *)stack_base;
197 proc->stack = stack_base + PROC_SIZE_WORDS;
198 if (CPU_SP_ON_EMPTY_SLOT)
203 proc = (Process *)(stack_base + stack_size / sizeof(cpustack_t) - PROC_SIZE_WORDS);
204 proc->stack = (cpustack_t *)proc;
205 if (CPU_SP_ON_EMPTY_SLOT)
209 proc_init_struct(proc);
210 proc->user_data = data;
212 #if CONFIG_KERN_HEAP | CONFIG_KERN_MONITOR | (ARCH & ARCH_EMUL)
213 proc->stack_base = stack_base;
214 proc->stack_size = stack_size;
217 proc->flags |= PF_FREESTACK;
221 #if CONFIG_KERN_PREEMPT
223 getcontext(&proc->context);
224 proc->context.uc_stack.ss_sp = proc->stack;
225 proc->context.uc_stack.ss_size = stack_size - PROC_SIZE_WORDS - 1;
226 proc->context.uc_link = NULL;
227 makecontext(&proc->context, (void (*)(void))proc_entry, 1, entry);
229 #else // !CONFIG_KERN_PREEMPT
233 /* Initialize process stack frame */
234 CPU_PUSH_CALL_FRAME(proc->stack, proc_exit);
235 CPU_PUSH_CALL_FRAME(proc->stack, entry);
237 /* Push a clean set of CPU registers for asm_switch_context() */
238 for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
239 CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
241 #endif // CONFIG_KERN_PREEMPT
243 #if CONFIG_KERN_MONITOR
244 monitor_add(proc, name);
247 /* Add to ready list */
248 ATOMIC(SCHED_ENQUEUE(proc));
254 * Return the name of the specified process.
256 * NULL is a legal argument and will return the name "<NULL>".
258 const char *proc_name(struct Process *proc)
260 #if CONFIG_KERN_MONITOR
261 return proc ? proc->monitor.name : "<NULL>";
268 /// Return the name of the currently running process
269 const char *proc_currentName(void)
271 return proc_name(proc_current());
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;
287 * Change the scheduling priority of a process.
289 * Process piorities are signed ints, whereas a larger integer value means
290 * higher scheduling priority. The default priority for new processes is 0.
291 * The idle process runs with the lowest possible priority: INT_MIN.
293 * A process with a higher priority always preempts lower priority processes.
294 * Processes of equal priority share the CPU time according to a simple
295 * round-robin policy.
297 * As a general rule to maximize responsiveness, compute-bound processes
298 * should be assigned negative priorities and tight, interactive processes
299 * should be assigned positive priorities.
301 * To avoid interfering with system background activities such as input
302 * processing, application processes should remain within the range -10
305 void proc_setPri(struct Process *proc, int pri)
307 if (proc->link.pri == pri)
310 proc->link.pri = pri;
312 if (proc != CurrentProcess)
315 //TODO: re-enqueue process
319 #endif // CONFIG_KERN_PRI
322 * Terminate the current process
326 TRACEMSG("%p:%s", CurrentProcess, proc_currentName());
328 #if CONFIG_KERN_MONITOR
329 monitor_remove(CurrentProcess);
334 * The following code is BROKEN.
335 * We are freeing our own stack before entering proc_schedule()
336 * BAJO: A correct fix would be to rearrange the scheduler with
337 * an additional parameter which frees the old stack/process
338 * after a context switch.
340 if (CurrentProcess->flags & PF_FREESTACK)
341 heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
342 heap_free(CurrentProcess);
345 #if (ARCH & ARCH_EMUL)
346 /* Reinsert process stack in free list */
347 PROC_ATOMIC(ADDHEAD(&StackFreeList, (Node *)CurrentProcess->stack_base));
350 * NOTE: At this point the first two words of what used
351 * to be our stack contain a list node. From now on, we
352 * rely on the compiler not reading/writing the stack.
354 #endif /* ARCH_EMUL */
356 CurrentProcess = NULL;
363 * Get the pointer to the current process
365 struct Process *proc_current(void)
367 return CurrentProcess;
371 * Get the pointer to the user data of the current process
373 iptr_t proc_currentUserData(void)
375 return CurrentProcess->user_data;