spinlock.c

这学期的os课程设计的

#include<stdio.h>
#include<unistd.h>
#include <sys/shm.h>
#include <errno.h>
#include <memory.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ipc.h>

#define LOCKED     1 /* spinlock is locked         */
#define UNLOCKED   0 /* spinlock is free           */
#define SPINLOCKS  3 /* the number of spinlocks    */
#define TERMINATED 1 /* the process is terminated*/
#define UNTERMINATED 0 /*the process is still running or not yet started*/

int *lock[SPINLOCKS];              /*the lock*/
int *terminate[SPINLOCKS];         /*share lock */
int *lockTerminate[SPINLOCKS];     /*share lock lock*/

//get spinlock
int get_spinlock( int *lockarea )
{	
	asm(
		"pushl %%eax;\n\t"
		"pushl %%ecx;\n\t"
		"l1: movl %1, %%eax;\n\t"	    
		"movl %2, %%ecx;"				
		"cmpxchg %%ecx, %0;\n\t"         
		"jne l1;\n\t"
		"popl %%ecx;\n\t"
		"popl %%eax;\n\t"		
		: "+m" (*lockarea) 
		:"i"(UNLOCKED),"i"(LOCKED)
		:"%eax","%ecx");			
	return 0;
}

int release_spinlock(int *lockarea)
{
	*lockarea = UNLOCKED;
}



main()
{
    int *shmptr;
    int shmid, i;
	int m_pid;						//监控进程m的进程标识符
	int p_pid;
	int status;
    /* Get shared memory to hold the data structures protected by
	one or more spinlocks. 74285 is a unique key, 1024 is size */
    shmid = shmget(74285, 3*SPINLOCKS*sizeof(int), IPC_CREAT|0600);
    if (shmid == -1) {
        fprintf(stderr, "shmget failed\n");
        exit(EXIT_FAILURE);
    }
    shmptr = shmat(shmid, 0, 0);   /* Attach to the阿 shared memory */
    if ( shmptr == (void *)-1) {
        fprintf(stderr, "shmat failed\n");
        exit(EXIT_FAILURE);
    }
	
	for (i = 0; i < 3* SPINLOCKS; i++)
	{
		shmptr[i]= 1;	
	}
	for (i=0; i < SPINLOCKS; i++)
	{
		lock[i] = shmptr + i;
		terminate[i] = shmptr + i + SPINLOCKS;
		*terminate[i] = 0;
		lockTerminate[i] = shmptr + i + 2*SPINLOCKS;
	}

	for (i=0; i < SPINLOCKS; i++)
	{
		if ( (p_pid=fork()) ==0 )
		{		
			get_spinlock(lock[i]);
			printf("process %d is running\n",i);
			get_spinlock(lockTerminate[i]);
			*terminate[i] = 1;	
			break;
		}
	}
	
	if (p_pid > 0) {
		i = 0;
		while(i < SPINLOCKS)
		{
			if(*lock[i]==LOCKED) {
				release_spinlock(lockTerminate[i]);
				release_spinlock(lock[i]);
			}
			if (*terminate[i] == 1)
			{
				printf("process %d is terminated!\n",i);
				i++;
			}
		}
		wait(&status);
	}
	
}