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linux系统内核流转浅析

编程日记 2023/11/01 14:46:25

SJTUBEAR 原创作品转载请注明出处《Linux内核分析》MOOC课程http://mooc.study.163.com/course/USTC-1000029000

我们通过简单地内核来模拟一下linux的系统调度，代码如下：

/**  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 */for(i=1;i<MAX_TASK_NUM;i++){memcpy(&task[i],&task[0],sizeof(tPCB));task[i].pid = i;task[i].state = -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];}/* start process 0 by task[0] */pid = 0;my_current_task = &task[pid];asm volatile("movl %1,%%esp
	"     /* set task[pid].thread.sp to esp */"pushl %1
	"             /* push ebp */"pushl %0
	"             /* push task[pid].thread.ip */"ret
	"                 /* pop task[pid].thread.ip to eip */"popl %%ebp
	": : "c" (task[pid].thread.ip),"d" (task[pid].thread.sp)    /* input c or d mean %ecx/%edx*/);
}   
void my_process(void)
{int i = 0;while(1){i++;if(i%10000000 == 0){printk(KERN_NOTICE "this is process %d -
",my_current_task->pid);if(my_need_sched == 1){my_need_sched = 0;my_schedule();}printk(KERN_NOTICE "this is process %d +
",my_current_task->pid);}     }
}