+/**
+ * \file
+ * <!--
+ * Copyright 2001,2004 Develer S.r.l. (http://www.develer.com/)
+ * Copyright 1999,2000,2001 Bernardo Innocenti <bernie@develer.com>
+ * All Rights Reserved.
+ * -->
+ *
+ * \brief Simple realtime multitasking scheduler.
+ * Context switching is only done cooperatively.
+ *
+ * \version $Id$
+ *
+ * \author Bernardo Innocenti <bernie@develer.com>
+ * \author Stefano Fedrigo <aleph@develer.com>
+ */
+
+/*
+ * $Log$
+ * Revision 1.1 2004/05/23 17:27:00 bernie
+ * Import kern/ subdirectory.
+ *
+ */
+
+#include "cpu.h"
+#include "proc_p.h"
+#include "proc.h"
+#include "event.h"
+#include "hw.h"
+#include <drv/kdebug.h>
+
+#include <string.h> /* memset() */
+
+/* CPU dependent context switching routines */
+extern void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
+
+/*
+ * The scheduer tracks ready and waiting processes
+ * by enqueuing them in these lists. A pointer to the currently
+ * running process is stored in the CurrentProcess pointer.
+ *
+ * NOTE: these variables are protected by DI/EI locking
+ */
+REGISTER Process *CurrentProcess;
+REGISTER List ProcReadyList;
+
+#if CONFIG_KERN_PREEMPTIVE
+/*
+ * The time sharing scheduler forces a task switch when
+ * the current process has consumed its quantum.
+ */
+uint16_t Quantum;
+#endif
+
+
+/* In Win32 we must emulate stack on the real process stack */
+#if (ARCH & ARCH_EMUL)
+extern List StackFreeList;
+#endif
+
+/* The main process (the one that executes main()) */
+struct Process MainProcess;
+
+static void proc_init_struct(Process* proc)
+{
+#if CONFIG_KERN_TIMER
+ INITEVENT_SIG(&proc->proc_timer.expire, proc, SIG_SINGLE);
+#endif
+
+#if CONFIG_KERN_SIGNALS
+ proc->sig_recv = 0;
+#endif
+
+#if CONFIG_KERN_HEAP
+ proc->flags = 0;
+#endif
+}
+
+void proc_init(void)
+{
+ INITLIST(&ProcReadyList);
+
+ /* We "promote" the current context into a real process. The only thing we have
+ to do is create a PCB and make it current. We don't need to setup the stack
+ pointer because it will be written the first time we switch to another process. */
+ proc_init_struct(&MainProcess);
+ CurrentProcess = &MainProcess;
+}
+
+
+/*!
+ * Create a new process, starting at the provided entry point.
+ *
+ * \return Process structure of new created process
+ * if successful, NULL otherwise.
+ */
+Process *proc_new(void (*entry)(void), size_t stacksize, cpustack_t *stack_base)
+{
+ Process *proc;
+ size_t i;
+ size_t proc_size_words = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t);
+#if CONFIG_KERN_HEAP
+ bool free_stack = false;
+#endif
+
+#if (ARCH & ARCH_EMUL)
+ /* Ignore stack provided by caller
+ * and use the large enough default instead
+ */
+ stack_base = (cpustack_t *)StackFreeList.head;
+ REMOVE((Node *)stack_base);
+ stacksize = DEF_STACKSIZE;
+#elif CONFIG_KERN_HEAP
+ /* Did the caller provide a stack for us? */
+ if (!stack_base)
+ {
+ /* Did the caller specify the desired stack size? */
+ if (!stacksize)
+ stacksize = CONFIG_KERN_DEFSTACKSIZE + sizeof(Process);
+
+ /* Allocate stack dinamically */
+ if (!(stack_base = heap_alloc(stacksize)))
+ return NULL;
+
+ free_stack = true;
+ }
+#else
+ /* Stack must have been provided by the user */
+ ASSERT(stack_base);
+ ASSERT(stacksize);
+#endif
+
+#ifdef _DEBUG
+ /* Fill-in the stack with a special marker to help debugging */
+ memset(stack_base, CONFIG_KERN_STACKFILLCODE, stacksize / sizeof(cpustack_t));
+#endif /* _DEBUG */
+
+ /* Initialize the process control block */
+ if (CPU_STACK_GROWS_UPWARD)
+ {
+ proc = (Process*)stack_base;
+ proc->stack = stack_base + proc_size_words;
+ if (CPU_SP_ON_EMPTY_SLOT)
+ proc->stack++;
+ }
+ else
+ {
+ proc = (Process*)(stack_base + stacksize / sizeof(cpustack_t) - proc_size_words);
+ proc->stack = (cpustack_t*)proc;
+ if (CPU_SP_ON_EMPTY_SLOT)
+ proc->stack--;
+ }
+
+ proc_init_struct(proc);
+
+#if CONFIG_KERN_HEAP
+ proc->stack_base = stack_base;
+ proc->stack_size = stack_size;
+ if (free_stack)
+ proc->flags |= PF_FREESTACK;
+#endif
+
+ /* Initialize process stack frame */
+ CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit);
+ CPU_PUSH_CALL_CONTEXT(proc->stack, entry);
+
+ /* Push a clean set of CPU registers for asm_switch_context() */
+ for (i = 0; i < CPU_SAVED_REGS_CNT; i++)
+ CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i));
+
+ /* Add to ready list */
+ DISABLE_INTS;
+ SCHED_ENQUEUE(proc);
+ ENABLE_INTS;
+
+ return proc;
+}
+
+
+/*!
+ * System scheduler: pass CPU control to the next process in
+ * the ready queue.
+ *
+ * Saving and restoring the context on the stack is done
+ * by a CPU-dependent support routine which must usually be
+ * written in assembly.
+ */
+void proc_schedule(void)
+{
+ /* This function must not have any "auto" variables, otherwise
+ * the compiler might put them on the stack of the process
+ * being switched out.
+ */
+ static Process *old_process;
+
+ /* Remember old process to save its context later */
+ old_process = CurrentProcess;
+ CurrentProcess = NULL;
+
+ /* Poll on the ready queue for the first ready process
+ */
+ for(;;) /* forever */
+ {
+ /* Do CPU specific idle processing (ARGH, should be moved to the end of the loop!) */
+ SCHEDULER_IDLE;
+
+ DISABLE_INTS;
+ if (!ISLISTEMPTY(&ProcReadyList))
+ {
+ /* Get process from ready list */
+ CurrentProcess = (Process *)ProcReadyList.head;
+ REMOVE((Node *)CurrentProcess);
+ ENABLE_INTS;
+ break;
+ }
+ ENABLE_INTS;
+ }
+
+ /* Optimization: don't switch contexts when the active
+ * process has not changed.
+ */
+ if (CurrentProcess != old_process)
+ {
+ static cpustack_t* dummy;
+
+#if CONFIG_KERN_PREEMPTIVE
+ /* Reset quantum for this process */
+ Quantum = CONFIG_KERN_QUANTUM;
+#endif
+
+ /* Save context of old process and switch to new process. If there is no
+ * old process, we save the old stack pointer into a dummy variable that
+ * we ignore. In fact, this happens only when the old process has just
+ * exited.
+ * TODO: Instead of physically clearing the process at exit time, a zombie
+ * list should be created.
+ */
+ asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
+ }
+
+ /* This RET resumes the execution on the new process */
+}
+
+
+/*!
+ * Terminate the current process
+ */
+void proc_exit(void)
+{
+#if CONFIG_KERN_HEAP
+ /* The following code is BROKEN.
+ * We are freeing our own stack before entering proc_schedule()
+ * BAJO: A correct fix would be to rearrange the scheduler with
+ * an additional parameter which frees the old stack/process
+ * after a context switch.
+ */
+ if (CurrentProcess->flags & PF_FREESTACK)
+ heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size);
+ heap_free(CurrentProcess);
+#endif
+
+#if (ARCH & ARCH_EMUL)
+#error This is wrong
+ /* Reinsert process stack in free list */
+ ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack
+ - (DEF_STACKSIZE / sizeof(cpustack_t))));
+
+ /* NOTE: At this point the first two words of what used
+ * to be our stack contain a list node. From now on, we
+ * rely on the compiler not reading/writing the stack.
+ */
+#endif /* ARCH_EMUL */
+
+ CurrentProcess = NULL;
+ proc_schedule();
+ /* not reached */
+}
+
+
+/*!
+ * Co-operative context switch
+ */
+void proc_switch(void)
+{
+ DISABLE_INTS;
+ SCHED_ENQUEUE(CurrentProcess);
+ ENABLE_INTS;
+ proc_schedule();
+}
+
+
+/*!
+ * Get the pointer to the current process
+ */
+struct Process *proc_current(void)
+{
+ return CurrentProcess;
+}
+
+
+#if 0 /* Simple testcase for the scheduler */
+
+/*!
+ * Proc scheduling test subthread 1
+ */
+static void NORETURN proc_test_thread1(void)
+{
+ for (;;)
+ {
+ kputs(">task 1\n");
+ timer_delay(50);
+ proc_switch();
+ }
+}
+
+/*!
+ * Proc scheduling test subthread 2
+ */
+static void NORETURN proc_test_thread2(void)
+{
+ for (;;)
+ {
+ kputs(">task 2\n");
+ timer_delay(75);
+ proc_switch();
+ }
+}
+
+static cpustack_t proc_test_stack1[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
+static cpustack_t proc_test_stack2[CONFIG_KERN_DEFSTACKSIZE/sizeof(cpustack_t)];
+
+/*!
+ * Proc scheduling test
+ */
+void NORETURN proc_test(void)
+{
+ proc_new(proc_test_thread1, sizeof(proc_test_stack1), proc_test_stack1);
+ proc_new(proc_test_thread2, sizeof(proc_test_stack2), proc_test_stack2);
+ kputs("Created tasks\n");
+
+ kputs("stack1:\n");
+ kdump(proc_test_stack1+sizeof(proc_test_stack1)-64, 64);
+ kputs("stack2:\n");
+ kdump(proc_test_stack2+sizeof(proc_test_stack1)-64, 64);
+
+ for (;;)
+ {
+ kputs(">main task\n");
+ timer_delay(93);
+ proc_switch();
+ }
+
+ ASSERT(false);
+}
+#endif