/**  linux/mykernel/mypcb.h**  Kernel internal PCB types**  Copyright (C) 2013  Mengning**/#define MAX_TASK_NUM        4
#define KERNEL_STACK_SIZE   1024*2 # unsigned long
/* CPU-specific state of this task */
struct Thread { //用于保存erp,espunsigned long      ip;unsigned long        sp;
};typedef struct PCB{int pid;volatile long state;   /* -1 unrunnable, 0 runnable, >0 stopped */unsigned long stack[KERNEL_STACK_SIZE];/* CPU-specific state of this task */struct Thread thread;unsigned long    task_entry;struct PCB *next;
}tPCB;void my_schedule(void);

/**  linux/mykernel/mymain.c**  Kernel internal my_start_kernel**  Copyright (C) 2013  Mengning**/
#include <linux/types.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/tty.h>
#include <linux/vmalloc.h>#include "mypcb.h"tPCB task[MAX_TASK_NUM];
tPCB * my_current_task = NULL;
volatile int my_need_sched = 0;void my_process(void);void __init my_start_kernel(void)
{int pid = 0;int i;/* Initialize process 0*/task[pid].pid = pid;task[pid].state = 0;/* -1 unrunnable, 0 runnable, >0 stopped */task[pid].task_entry = task[pid].thread.ip = (unsigned long)my_process;task[pid].thread.sp = (unsigned long)&task[pid].stack[KERNEL_STACK_SIZE-1];task[pid].next = &task[pid];/*fork more process，每个进程都有自己的堆栈，并指向下一个进程 */for(i=1;i<MAX_TASK_NUM;i++){memcpy(&task[i],&task[0],sizeof(tPCB));task[i].pid = i;//*(&task[i].stack[KERNEL_STACK_SIZE-1] - 1) = (unsigned long)&task[i].stack[KERNEL_STACK_SIZE-1];task[i].thread.sp = (unsigned long)(&task[i].stack[KERNEL_STACK_SIZE-1]);task[i].next = task[i-1].next;task[i-1].next = &task[i];}/* 从第0个进程开始 */pid = 0;my_current_task = &task[pid];asm volatile("movl %1,%%esp\n\t"     /* set task[pid].thread.sp to esp */"pushl %1\n\t"             /* push ebp */"pushl %0\n\t"             /* push task[pid].thread.ip */"ret\n\t"                 /* pop task[pid].thread.ip to eip */: : "c" (task[pid].thread.ip),"d" (task[pid].thread.sp)    /* input c or d mean %ecx/%edx*/);
} int i = 0;void my_process(void)
{    while(1){i++;if(i%10000000 == 0){printk(KERN_NOTICE "this is process %d -\n",my_current_task->pid);if(my_need_sched == 1) //ny_need_sched=1时才会调度{my_need_sched = 0;my_schedule();}printk(KERN_NOTICE "this is process %d +\n",my_current_task->pid);}     }
}

/**  linux/mykernel/myinterrupt.c**  Kernel internal my_timer_handler**  Copyright (C) 2013  Mengning**/
#include <linux/types.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/tty.h>
#include <linux/vmalloc.h>#include "mypcb.h"extern tPCB task[MAX_TASK_NUM];
extern tPCB * my_current_task;
extern volatile int my_need_sched;
volatile int time_count = 0;/** Called by timer interrupt.* it runs in the name of current running process,* so it use kernel stack of current running process*/
void my_timer_handler(void)
{
#if 1if(time_count%1000 == 0 && my_need_sched != 1) //设置时间片大小，时间片用完设置调度标志{printk(KERN_NOTICE ">>>my_timer_handler here<<<\n");my_need_sched = 1;} time_count ++ ;
#endifreturn;
}void my_schedule(void)
{tPCB * next;把当前tPCB * prev;if(my_current_task == NULL || my_current_task->next == NULL){return;}printk(KERN_NOTICE ">>>my_schedule<<<\n");/* schedule */next = my_current_task->next; //把当前进程的下一个进程赋值给nextprev = my_current_task;if(next->state == 0)/* 下一个进程正在执行*/{        my_current_task = next; printk(KERN_NOTICE ">>>switch %d to %d<<<\n",prev->pid,next->pid);  /* switch to next process */asm volatile(    //切换进程"pushl %%ebp\n\t"         /* save ebp */"movl %%esp,%0\n\t"     /* 把当前进程的esp赋给prev->thread.sp，保存*/"movl %2,%%esp\n\t"     /* 把下一进程的next->thread.sp赋给esp */"movl $1f,%1\n\t"       /* save eip */    "pushl %3\n\t" "ret\n\t"                 /*把下一进程的next->thread.ip进栈*/"1:\t"                  /* 下一进程开始执行*/"popl %%ebp\n\t": "=m" (prev->thread.sp),"=m" (prev->thread.ip): "m" (next->thread.sp),"m" (next->thread.ip)); }  return;
}