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 BeRTOS Kernel core (Process scheduler).
36 * \author Bernie Innocenti <bernie@codewiz.org>
38 * $WIZ$ module_name = "kernel"
39 * $WIZ$ module_configuration = "bertos/cfg/cfg_proc.h"
40 * $WIZ$ module_depends = "switch_ctx", "coop"
41 * $WIZ$ module_supports = "not atmega103"
47 #include "cfg/cfg_proc.h"
48 #include "cfg/cfg_monitor.h"
50 #include <cfg/compiler.h>
52 #if CONFIG_KERN_PREEMPT
53 #include <cfg/debug.h> // ASSERT()
56 #include <cpu/types.h> // cpu_stack_t
57 #include <cpu/frame.h> // CPU_SAVED_REGS_CNT
60 * Forward declaration. The definition of struct Process is private to the
61 * scheduler and hidden in proc_p.h.
66 * Initialize the process subsystem (kernel).
67 * It must be called before using any process related function.
72 * Create a new named process and schedules it for execution.
74 * When defining the stacksize take into account that you may want at least:
75 * \li save all the registers for each nested function call;
76 * \li have memory for the struct Process, which is positioned at the bottom
78 * \li have some memory for temporary variables inside called functions.
80 * The value given by CONFIG_KERN_MINSTACKSIZE is rather safe to use in the first place.
84 * proc_new(entry, data, stacksize, stack)
86 * is a more convenient way to create a process, as you don't have to specify
89 * \param name Name of the process (currently unused).
90 * \param entry Function that the process will execute.
91 * \param data Pointer to user data.
92 * \param stacksize Length of the stack.
93 * \param stack Pointer to the memory area to be used as a stack.
95 struct Process *proc_new_with_name(const char *name, void (*entry)(void), iptr_t data, size_t stacksize, cpu_stack_t *stack);
97 #if !CONFIG_KERN_MONITOR
98 #define proc_new(entry,data,size,stack) proc_new_with_name(NULL,(entry),(data),(size),(stack))
100 #define proc_new(entry,data,size,stack) proc_new_with_name(#entry,(entry),(data),(size),(stack))
104 * Terminate the execution of the current process.
106 void proc_exit(void);
109 * Co-operative context switch.
111 * The process that calls this function will release the CPU before its cpu quantum
112 * expires, the scheduler will run to select the next process that will take control
114 * \note This function is available only if CONFIG_KERN is enabled
115 * \sa cpu_relax(), which is the recommended method to release the cpu.
117 void proc_yield(void);
119 void proc_rename(struct Process *proc, const char *name);
120 const char *proc_name(struct Process *proc);
121 const char *proc_currentName(void);
124 * Return a pointer to the user data of the current process.
126 * To obtain user data, just call this function inside the process. Remember to cast
127 * the returned pointer to the correct type.
128 * \return Pointer to the user data of the current process.
130 iptr_t proc_currentUserData(void);
132 int proc_testSetup(void);
133 int proc_testRun(void);
134 int proc_testTearDown(void);
137 * Return the context structure of the currently running process.
139 * The details of the Process structure are private to the scheduler.
140 * The address returned by this function is an opaque pointer that can
141 * be passed as an argument to other process-related functions.
143 INLINE struct Process *proc_current(void)
145 extern struct Process *CurrentProcess;
146 return CurrentProcess;
150 void proc_setPri(struct Process *proc, int pri);
152 INLINE void proc_setPri(UNUSED_ARG(struct Process *,proc), UNUSED_ARG(int, pri))
158 * Disable preemptive task switching.
160 * The scheduler maintains a global nesting counter. Task switching is
161 * effectively re-enabled only when the number of calls to proc_permit()
162 * matches the number of calls to proc_forbid().
164 * \note Calling functions that could sleep while task switching is disabled
165 * is dangerous and unsupported.
167 * \note calling proc_forbid() from within an interrupt is illegal and
170 * \note proc_permit() expands inline to 1-2 asm instructions, so it's a
171 * very efficient locking primitive in simple but performance-critical
172 * situations. In all other cases, semaphores offer a more flexible and
173 * fine-grained locking primitive.
177 INLINE void proc_forbid(void)
179 #if CONFIG_KERN_PREEMPT
180 extern cpu_atomic_t _preempt_forbid_cnt;
182 * We don't need to protect the counter against other processes.
183 * The reason why is a bit subtle.
185 * If a process gets here, preempt_forbid_cnt can be either 0,
186 * or != 0. In the latter case, preemption is already disabled
187 * and no concurrency issues can occur.
189 * In the former case, we could be preempted just after reading the
190 * value 0 from memory, and a concurrent process might, in fact,
191 * bump the value of preempt_forbid_cnt under our nose!
193 * BUT: if this ever happens, then we won't get another chance to
194 * run until the other process calls proc_permit() to re-enable
195 * preemption. At this point, the value of preempt_forbid_cnt
196 * must be back to 0, and thus what we had originally read from
197 * memory happens to be valid.
199 * No matter how hard you think about it, and how complicated you
200 * make your scenario, the above holds true as long as
201 * "preempt_forbid_cnt != 0" means that no task switching is
204 ++_preempt_forbid_cnt;
207 * Make sure _preempt_forbid_cnt is flushed to memory so the
208 * preemption softirq will see the correct value from now on.
215 * Re-enable preemptive task switching.
219 INLINE void proc_permit(void)
221 #if CONFIG_KERN_PREEMPT
224 * This is to ensure any global state changed by the process gets
225 * flushed to memory before task switching is re-enabled.
228 extern cpu_atomic_t _preempt_forbid_cnt;
229 /* No need to protect against interrupts here. */
230 ASSERT(_preempt_forbid_cnt != 0);
231 --_preempt_forbid_cnt;
234 * This ensures _preempt_forbid_cnt is flushed to memory immediately
235 * so the preemption interrupt sees the correct value.
243 * \return true if preemptive task switching is allowed.
244 * \note This accessor is needed because _preempt_forbid_cnt
245 * must be absoultely private.
247 INLINE bool proc_allowed(void)
249 #if CONFIG_KERN_PREEMPT
250 extern cpu_atomic_t _preempt_forbid_cnt;
251 return (_preempt_forbid_cnt == 0);
258 * Execute a block of \a CODE atomically with respect to task scheduling.
260 #define PROC_ATOMIC(CODE) \
267 #ifndef CONFIG_KERN_MINSTACKSIZE
269 #if (ARCH & ARCH_EMUL)
270 /* We need a large stack because system libraries are bloated */
271 #define CONFIG_KERN_MINSTACKSIZE 65536
274 * Default stack size for each thread, in bytes.
276 * The goal here is to allow a minimal task to save all of its
277 * registers twice, plus push a maximum of 32 variables on the
280 * The actual size computed by the default formula is:
286 * Note that on most 16bit architectures, interrupts will also
287 * run on the stack of the currently running process. Nested
288 * interrupts will greatly increases the amount of stack space
289 * required per process. Use irqmanager to minimize stack
292 #define CONFIG_KERN_MINSTACKSIZE \
293 (CPU_SAVED_REGS_CNT * 2 * sizeof(cpu_stack_t) \
298 /* Memory fill codes to help debugging */
299 #if CONFIG_KERN_MONITOR
300 #include <cpu/types.h>
301 #if (SIZEOF_CPUSTACK_T == 1)
302 /* 8bit cpu_stack_t */
303 #define CONFIG_KERN_STACKFILLCODE 0xA5
304 #define CONFIG_KERN_MEMFILLCODE 0xDB
305 #elif (SIZEOF_CPUSTACK_T == 2)
306 /* 16bit cpu_stack_t */
307 #define CONFIG_KERN_STACKFILLCODE 0xA5A5
308 #define CONFIG_KERN_MEMFILLCODE 0xDBDB
309 #elif (SIZEOF_CPUSTACK_T == 4)
310 /* 32bit cpu_stack_t */
311 #define CONFIG_KERN_STACKFILLCODE 0xA5A5A5A5UL
312 #define CONFIG_KERN_MEMFILLCODE 0xDBDBDBDBUL
313 #elif (SIZEOF_CPUSTACK_T == 8)
314 /* 64bit cpu_stack_t */
315 #define CONFIG_KERN_STACKFILLCODE 0xA5A5A5A5A5A5A5A5ULL
316 #define CONFIG_KERN_MEMFILLCODE 0xDBDBDBDBDBDBDBDBULL
318 #error No cpu_stack_t size supported!
322 #endif /* KERN_PROC_H */