* Copyright 1999, 2000, 2001, 2008 Bernie Innocenti <bernie@codewiz.org>
* -->
*
- * \brief Process scheduler (public interface).
+ * \brief BeRTOS Kernel core (Process scheduler).
*
* \version $Id$
* \author Bernie Innocenti <bernie@codewiz.org>
+ *
+ * $WIZ$ module_name = "kernel"
+ * $WIZ$ module_configuration = "bertos/cfg/cfg_proc.h"
+ * $WIZ$ module_depends = "switch_ctx", "coop"
+ * $WIZ$ module_supports = "not atmega103"
*/
+
#ifndef KERN_PROC_H
#define KERN_PROC_H
-#include "cfg/cfg_kern.h"
+#include "cfg/cfg_proc.h"
+#include "cfg/cfg_monitor.h"
+
#include <cfg/compiler.h>
#if CONFIG_KERN_PREEMPT
#include <cfg/debug.h> // ASSERT()
#endif
-#include <cpu/types.h> // cpustack_t
+#include <cpu/types.h> // cpu_stack_t
+#include <cpu/frame.h> // CPU_SAVED_REGS_CNT
/*
* Forward declaration. The definition of struct Process is private to the
*/
struct Process;
-/* Task scheduling services */
+/**
+ * Initialize the process subsystem (kernel).
+ * It must be called before using any process related function.
+ */
void proc_init(void);
-struct Process *proc_new_with_name(const char* name, void (*entry)(void), iptr_t data, size_t stacksize, cpustack_t *stack);
+
+/**
+ * Create a new named process and schedules it for execution.
+ *
+ * When defining the stacksize take into account that you may want at least:
+ * \li save all the registers for each nested function call;
+ * \li have memory for the struct Process, which is positioned at the bottom
+ * of the stack;
+ * \li have some memory for temporary variables inside called functions.
+ *
+ * The value given by CONFIG_KERN_MINSTACKSIZE is rather safe to use in the first place.
+ *
+ * \note The function
+ * \code
+ * proc_new(entry, data, stacksize, stack)
+ * \endcode
+ * is a more convenient way to create a process, as you don't have to specify
+ * the name.
+ *
+ * \param name Name of the process (currently unused).
+ * \param entry Function that the process will execute.
+ * \param data Pointer to user data.
+ * \param stacksize Length of the stack.
+ * \param stack Pointer to the memory area to be used as a stack.
+ */
+struct Process *proc_new_with_name(const char *name, void (*entry)(void), iptr_t data, size_t stacksize, cpu_stack_t *stack);
#if !CONFIG_KERN_MONITOR
#define proc_new(entry,data,size,stack) proc_new_with_name(NULL,(entry),(data),(size),(stack))
#define proc_new(entry,data,size,stack) proc_new_with_name(#entry,(entry),(data),(size),(stack))
#endif
+/**
+ * Terminate the execution of the current process.
+ */
void proc_exit(void);
+
+/**
+ * Co-operative context switch.
+ *
+ * The process that calls this function will release the CPU before its cpu quantum
+ * expires, the scheduler will run to select the next process that will take control
+ * of the processor.
+ * \note This function is available only if CONFIG_KERN is enabled
+ * \sa cpu_relax(), which is the recommended method to release the cpu.
+ */
void proc_yield(void);
-#define proc_switch proc_yield /* OBSOLETE */
+
+void proc_rename(struct Process *proc, const char *name);
+const char *proc_name(struct Process *proc);
+const char *proc_currentName(void);
+
+/**
+ * Return a pointer to the user data of the current process.
+ *
+ * To obtain user data, just call this function inside the process. Remember to cast
+ * the returned pointer to the correct type.
+ * \return Pointer to the user data of the current process.
+ */
+iptr_t proc_currentUserData(void);
int proc_testSetup(void);
int proc_testRun(void);
int proc_testTearDown(void);
-struct Process *proc_current(void);
-iptr_t proc_currentUserData(void);
-void proc_rename(struct Process *proc, const char *name);
-const char *proc_name(struct Process *proc);
-const char *proc_currentName(void);
+/**
+ * Return the context structure of the currently running process.
+ *
+ * The details of the Process structure are private to the scheduler.
+ * The address returned by this function is an opaque pointer that can
+ * be passed as an argument to other process-related functions.
+ */
+INLINE struct Process *proc_current(void)
+{
+ extern struct Process *CurrentProcess;
+ return CurrentProcess;
+}
#if CONFIG_KERN_PRI
void proc_setPri(struct Process *proc, int pri);
* \note Calling functions that could sleep while task switching is disabled
* is dangerous and unsupported.
*
+ * \note calling proc_forbid() from within an interrupt is illegal and
+ * meaningless.
+ *
* \note proc_permit() expands inline to 1-2 asm instructions, so it's a
* very efficient locking primitive in simple but performance-critical
* situations. In all other cases, semaphores offer a more flexible and
INLINE void proc_forbid(void)
{
#if CONFIG_KERN_PREEMPT
- // No need to protect against interrupts here.
- extern int preempt_forbid_cnt;
- ++preempt_forbid_cnt;
+ extern cpu_atomic_t _preempt_forbid_cnt;
+ /*
+ * We don't need to protect the counter against other processes.
+ * The reason why is a bit subtle.
+ *
+ * If a process gets here, preempt_forbid_cnt can be either 0,
+ * or != 0. In the latter case, preemption is already disabled
+ * and no concurrency issues can occur.
+ *
+ * In the former case, we could be preempted just after reading the
+ * value 0 from memory, and a concurrent process might, in fact,
+ * bump the value of preempt_forbid_cnt under our nose!
+ *
+ * BUT: if this ever happens, then we won't get another chance to
+ * run until the other process calls proc_permit() to re-enable
+ * preemption. At this point, the value of preempt_forbid_cnt
+ * must be back to 0, and thus what we had originally read from
+ * memory happens to be valid.
+ *
+ * No matter how hard you think about it, and how complicated you
+ * make your scenario, the above holds true as long as
+ * "preempt_forbid_cnt != 0" means that no task switching is
+ * possible.
+ */
+ ++_preempt_forbid_cnt;
/*
- * Make sure preempt_forbid_cnt is flushed to memory so the
+ * Make sure _preempt_forbid_cnt is flushed to memory so the
* preemption softirq will see the correct value from now on.
*/
MEMORY_BARRIER;
* flushed to memory before task switching is re-enabled.
*/
MEMORY_BARRIER;
-
+ extern cpu_atomic_t _preempt_forbid_cnt;
/* No need to protect against interrupts here. */
- extern int preempt_forbid_cnt;
- --preempt_forbid_cnt;
- ASSERT(preempt_forbid_cnt >= 0);
+ ASSERT(_preempt_forbid_cnt != 0);
+ --_preempt_forbid_cnt;
/*
- * This ensures preempt_forbid_cnt is flushed to memory immediately
+ * This ensures _preempt_forbid_cnt is flushed to memory immediately
* so the preemption interrupt sees the correct value.
*/
MEMORY_BARRIER;
#endif
}
+/**
+ * \return true if preemptive task switching is allowed.
+ * \note This accessor is needed because _preempt_forbid_cnt
+ * must be absoultely private.
+ */
+INLINE bool proc_allowed(void)
+{
+ #if CONFIG_KERN_PREEMPT
+ extern cpu_atomic_t _preempt_forbid_cnt;
+ return (_preempt_forbid_cnt == 0);
+ #else
+ return true;
+ #endif
+}
/**
* Execute a block of \a CODE atomically with respect to task scheduling.
* stack.
*
* The actual size computed by the default formula is:
- * AVR: 102
- * i386: 156
- * ARM: 164
- * x86_64: 184
+ * \li AVR: 102
+ * \li i386: 156
+ * \li ARM: 164
+ * \li x86_64: 184
*
* Note that on most 16bit architectures, interrupts will also
* run on the stack of the currently running process. Nested
* usage.
*/
#define CONFIG_KERN_MINSTACKSIZE \
- (CPU_SAVED_REGS_CNT * 2 * sizeof(cpustack_t) \
- + 32 * sizeof(int))
+ (CPU_SAVED_REGS_CNT * 2 * sizeof(cpu_stack_t) \
+ + 48 * sizeof(int))
#endif
#endif
-#define CONFIG_PROC_DEFSTACKSIZE CONFIG_KERN_MINSTACKSIZE // OBSOLETE
-
/* Memory fill codes to help debugging */
#if CONFIG_KERN_MONITOR
#include <cpu/types.h>
#if (SIZEOF_CPUSTACK_T == 1)
- /* 8bit cpustack_t */
+ /* 8bit cpu_stack_t */
#define CONFIG_KERN_STACKFILLCODE 0xA5
#define CONFIG_KERN_MEMFILLCODE 0xDB
#elif (SIZEOF_CPUSTACK_T == 2)
- /* 16bit cpustack_t */
+ /* 16bit cpu_stack_t */
#define CONFIG_KERN_STACKFILLCODE 0xA5A5
#define CONFIG_KERN_MEMFILLCODE 0xDBDB
#elif (SIZEOF_CPUSTACK_T == 4)
- /* 32bit cpustack_t */
+ /* 32bit cpu_stack_t */
#define CONFIG_KERN_STACKFILLCODE 0xA5A5A5A5UL
#define CONFIG_KERN_MEMFILLCODE 0xDBDBDBDBUL
#elif (SIZEOF_CPUSTACK_T == 8)
- /* 64bit cpustack_t */
+ /* 64bit cpu_stack_t */
#define CONFIG_KERN_STACKFILLCODE 0xA5A5A5A5A5A5A5A5ULL
#define CONFIG_KERN_MEMFILLCODE 0xDBDBDBDBDBDBDBDBULL
#else
- #error No cpustack_t size supported!
+ #error No cpu_stack_t size supported!
#endif
#endif
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