操作系统中的临界区是什么

t;
#include
#include
#include
#define false 0
#define true 1

int flag[2];
int turn;

void P0()
{
while(true)
{
flag[0]=true;
turn = 1;
while(flag[1]&&turn==1)
;
printf ("P0 is in critical section.\n");
printf ("P0 is going to leave critical section.\n");
flag[0]=false;
printf ("P0 is out of critical section.\n");
}
}
void P1()
{
while(true)
{
flag[1]=true;
turn = 0;
while(flag[0]&&turn==0)
;
printf ("P1 is in critical section.\n");
printf ("P1 is going to leave critical section.\n");
flag[1]=false;
printf ("P1 is out of critical section.\n");
}
}
int main()
{
pthread_t pid0;
pthread_t pid1;
flag[0]=false;
flag[1]=false;
pthread_create(&pid0, NULL, (void*)P0, NULL);
pthread_create(&pid1, NULL, (void*)P1, NULL);
pthread_join(pid0, NULL);
pthread_join(pid1, NULL);
exit(0);
}
Linux系统下实现

每个进程中访问临界资源的那段代码