sem.c

来自「操作系统实验一到四 哈尔滨工业大学计算机学院的」· C语言 代码 · 共 139 行

#include <errno.h>
#include <unistd.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <asm/segment.h>
#include <asm/system.h>

#define PC_BUFFER_MAX 10

int in,out; //生产者当前处理缓存区的指针
int pc_Buffers[PC_BUFFER_MAX];

sem_t array[NR_SEMS];
char myname[NR_MAX];
void sem_init()
{
    int i;
    for(i=0; i<NR_SEMS; i++)
    {
	array[i].used=0;
	array[i].value=0;
	array[i].wait=NULL;
    };
}

sem_t * sys_sem_open(const char *name, unsigned int value)
{
    cli();
    char c;
    int size=0,i,pos=-1;
    for(i=0;i<NR_MAX;i++)
		myname[i]='\0';
    while((c=get_fs_byte(name+size++))!='\0');
    if (size>NR_MAX){ sti(); return NULL;}
    
    for ( i = 0 ;i<size; i++)
        myname[i] = get_fs_byte(name+i);



    for(i=0;i<NR_SEMS;i++)
    {
        if(pos==-1&&array[i].used==0)
            pos=i;
        if(!strcmp(myname,array[i].name))
        {
            sti();
            return array+i;
        }
    }
    if(pos==-1)
    {
        sti();
        return NULL;
    }
    array[pos].value=value;
    array[pos].used=1;
    array[pos].wait=NULL;
    for(i=0;i<size;i++)
        array[pos].name[i]=myname[i];
    
    sti();
    return array+pos;
}

int sys_sem_wait(sem_t *sem)
{
    cli();
    sem->value--;
    /*fprintk(1,"sem->name=%s\nsem->value=%d\nwait_process_pid=%ld\n",sem->name,sem->value,sem->wait->pid);*/
    if(sem->value<0)
	sleep_on(&(sem->wait));
    sti();
    return 0;
}

int sys_sem_post(sem_t *sem)
{
    cli();
    sem->value++;
   /* fprintk(1,"sem->name=%s\nsem->value=%d\npost_process_pid=%ld\n",sem->name,sem->value,sem->wait->pid);*/
    if(sem->value<=0)
    {
        wake_up(&(sem->wait));

    }
    sti();
    return 0;
}

int sys_sem_unlink(const char *name)
{
    cli();
    int i,flag=0,size;
    char c;
    for(i=0;i<NR_MAX;i++)
		myname[i]='\0';
    for(size=0;(c=get_fs_byte(name+size))!='\0';size++)
    {
		if(size>=NR_MAX-1)
		{
		    sti();
			return -1;
		}
		else
                	myname[size]=c;
    }
    for(i=0;i<NR_SEMS;i++)
    {
        if(!strcmp(myname,array[i].name))
        {
            flag=1;
            array[i].used=0;
            array[i].value=0;
            array[i].wait=NULL;
            sti();
            return 0;
        }
    }
    sti();
    return -1;
}

int sys_pcinsert(int item)
{
    
    pc_Buffers[in]=item;
    in=(in+1)%PC_BUFFER_MAX;
    return 0;
}

int sys_pcdelete(void)
{
    int item;
    item=pc_Buffers[out];
    out=(out+1)% PC_BUFFER_MAX;
    return item;
}