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 Process scheduler (public interface).
36 * \author Bernie Innocenti <bernie@codewiz.org>
41 #include "cfg/cfg_kern.h"
42 #include <cfg/compiler.h>
44 #if CONFIG_KERN_PREEMPT
45 #include <cfg/debug.h> // ASSERT()
48 #include <cpu/types.h> // cpustack_t
49 #include <cpu/frame.h> // CPU_SAVED_REGS_CNT
52 * Forward declaration. The definition of struct Process is private to the
53 * scheduler and hidden in proc_p.h.
57 /* Task scheduling services */
59 struct Process *proc_new_with_name(const char* name, void (*entry)(void), iptr_t data, size_t stacksize, cpustack_t *stack);
61 #if !CONFIG_KERN_MONITOR
62 #define proc_new(entry,data,size,stack) proc_new_with_name(NULL,(entry),(data),(size),(stack))
64 #define proc_new(entry,data,size,stack) proc_new_with_name(#entry,(entry),(data),(size),(stack))
68 void proc_yield(void);
70 int proc_testSetup(void);
71 int proc_testRun(void);
72 int proc_testTearDown(void);
74 struct Process *proc_current(void);
75 iptr_t proc_currentUserData(void);
76 void proc_rename(struct Process *proc, const char *name);
77 const char *proc_name(struct Process *proc);
78 const char *proc_currentName(void);
81 void proc_setPri(struct Process *proc, int pri);
83 INLINE void proc_setPri(UNUSED_ARG(struct Process *,proc), UNUSED_ARG(int, pri))
89 * Disable preemptive task switching.
91 * The scheduler maintains a global nesting counter. Task switching is
92 * effectively re-enabled only when the number of calls to proc_permit()
93 * matches the number of calls to proc_forbid().
95 * \note Calling functions that could sleep while task switching is disabled
96 * is dangerous and unsupported.
98 * \note calling proc_forbid() from within an interrupt is illegal and
101 * \note proc_permit() expands inline to 1-2 asm instructions, so it's a
102 * very efficient locking primitive in simple but performance-critical
103 * situations. In all other cases, semaphores offer a more flexible and
104 * fine-grained locking primitive.
108 INLINE void proc_forbid(void)
110 #if CONFIG_KERN_PREEMPT
111 extern int _preempt_forbid_cnt;
113 * We don't need to protect the counter against other processes.
114 * The reason why is a bit subtle.
116 * If a process gets here, preempt_forbid_cnt can be either 0,
117 * or != 0. In the latter case, preemption is already disabled
118 * and no concurrency issues can occur.
120 * In the former case, we could be preempted just after reading the
121 * value 0 from memory, and a concurrent process might, in fact,
122 * bump the value of preempt_forbid_cnt under our nose!
124 * BUT: if this ever happens, then we won't get another chance to
125 * run until the other process calls proc_permit() to re-enable
126 * preemption. At this point, the value of preempt_forbid_cnt
127 * must be back to 0, and thus what we had originally read from
128 * memory happens to be valid.
130 * No matter how hard you think about it, and how complicated you
131 * make your scenario, the above holds true as long as
132 * "preempt_forbid_cnt != 0" means that no task switching is
135 ++_preempt_forbid_cnt;
138 * Make sure _preempt_forbid_cnt is flushed to memory so the
139 * preemption softirq will see the correct value from now on.
146 * Re-enable preemptive task switching.
150 INLINE void proc_permit(void)
152 #if CONFIG_KERN_PREEMPT
155 * This is to ensure any global state changed by the process gets
156 * flushed to memory before task switching is re-enabled.
159 extern int _preempt_forbid_cnt;
160 /* No need to protect against interrupts here. */
161 ASSERT(_preempt_forbid_cnt != 0);
162 --_preempt_forbid_cnt;
165 * This ensures _preempt_forbid_cnt is flushed to memory immediately
166 * so the preemption interrupt sees the correct value.
174 * \return true if preemptive task switching is allowed.
175 * \note This accessor is needed because _preempt_forbid_cnt
176 * must be absoultely private.
178 INLINE bool proc_allowed(void)
180 #if CONFIG_KERN_PREEMPT
181 extern int _preempt_forbid_cnt;
182 return (_preempt_forbid_cnt == 0);
189 * Execute a block of \a CODE atomically with respect to task scheduling.
191 #define PROC_ATOMIC(CODE) \
198 #ifndef CONFIG_KERN_MINSTACKSIZE
200 #if (ARCH & ARCH_EMUL)
201 /* We need a large stack because system libraries are bloated */
202 #define CONFIG_KERN_MINSTACKSIZE 65536
205 * Default stack size for each thread, in bytes.
207 * The goal here is to allow a minimal task to save all of its
208 * registers twice, plus push a maximum of 32 variables on the
211 * The actual size computed by the default formula is:
217 * Note that on most 16bit architectures, interrupts will also
218 * run on the stack of the currently running process. Nested
219 * interrupts will greatly increases the amount of stack space
220 * required per process. Use irqmanager to minimize stack
223 #define CONFIG_KERN_MINSTACKSIZE \
224 (CPU_SAVED_REGS_CNT * 2 * sizeof(cpustack_t) \
229 /* Memory fill codes to help debugging */
230 #if CONFIG_KERN_MONITOR
231 #include <cpu/types.h>
232 #if (SIZEOF_CPUSTACK_T == 1)
233 /* 8bit cpustack_t */
234 #define CONFIG_KERN_STACKFILLCODE 0xA5
235 #define CONFIG_KERN_MEMFILLCODE 0xDB
236 #elif (SIZEOF_CPUSTACK_T == 2)
237 /* 16bit cpustack_t */
238 #define CONFIG_KERN_STACKFILLCODE 0xA5A5
239 #define CONFIG_KERN_MEMFILLCODE 0xDBDB
240 #elif (SIZEOF_CPUSTACK_T == 4)
241 /* 32bit cpustack_t */
242 #define CONFIG_KERN_STACKFILLCODE 0xA5A5A5A5UL
243 #define CONFIG_KERN_MEMFILLCODE 0xDBDBDBDBUL
244 #elif (SIZEOF_CPUSTACK_T == 8)
245 /* 64bit cpustack_t */
246 #define CONFIG_KERN_STACKFILLCODE 0xA5A5A5A5A5A5A5A5ULL
247 #define CONFIG_KERN_MEMFILLCODE 0xDBDBDBDBDBDBDBDBULL
249 #error No cpustack_t size supported!
253 #endif /* KERN_PROC_H */