sched.c

用于汇编领域的,运用于OS的MAIN函数.基于硬件基础的源代码

#include "hos.h"
struct task_struct * next_p(){
	// select next processor
	// skip pid=0 when there is other processes
	if (current->next_run->pid==0)
	   return (current->next_run->next_run);
	return (current->next_run);
}

#define switch_to(prev, next, last) do { \
	asm volatile("pushl %%esi\n\t"  \
			"pushl %%edi\n\t"  \
			"pushl %%ebp\n\t" \
			"movl %%esp, %0\n\t" /*save esp*/ \
			"movl %2, %%esp\n\t" /*restore esp*/ \
			"movl $1f, %1\n\t" /*save eip*/ \
			"pushl %3\n\t" /*restore eip*/ \
			"ret\n\t" \
			"1:\t" \
			"popl %%ebp\n\t"  \
			"popl %%edi\n\t"  \
			"popl %%esi\n\t"  \
			:"=m"(prev->esp), "=m"(prev->eip) \
			:"m"(next->esp), "m"(next->eip) \
			 ); \
}while (0)
void schedule(void){
	struct task_struct *prev, *next;
	unsigned long *pgdir_loc;
/*
    // for hacking exec. skip scheduling
	if (current->pid==1) {
		  return;
    }
*/

	//unsigned long addr; //float x=0.0; int i;
	if (!current->need_reschedule) return;
	//get next process and start it
	prev=current;
	current->need_reschedule=0; // reset
	next=next_p();
	current=next;
	pgdir_loc = current->mm.pgdir; // location of pgdir of current
	// change page directory
	__asm__ ("pushl %%eax\n\t"
	         "movl %0, %%eax\n\t"
			 "movl %%eax, %%cr3\n\t"
			 "popl %%eax\n\t"
			 ::"m"(pgdir_loc));
	if (next!=prev){
		//printk("about to switch. current is %x\n",current);
		/*
		for(i=0;i<100000000;i++)
			x=x+1.0;
			*/
		// take care tss first
		//init_tss.esp0 = next->esp0; we don't handel user mode process
		//printk("bef switch. stack top of next is %x\n", next->esp);
		//printk("and stack is "); 
		//display_regs((struct pt_regs *)next->esp);
		//printk("and ret address is %x\n", next->eip);
		switch_to(prev,next,prev);
		/*
		asm("popl %%eax\n\t"
		    "movl %%eax, %0\n\t"
		    :"=m"(addr):);
		printk("p1_body is %x, return addr: %x\n", p1_body, addr);
		for(;;);
		*/
	}
}