#include<unistd.h>
#include<stdio.h>
#include<stdlib.h>
#include<fcntl.h>
#include<errno.h>
#include<pthread.h>
#include<stddef.h>
#include<stdint.h>

#define DIE(x)\
{\
	fprintf(stderr, "Assertion failed: " #x " file: %s, line:%d, errno:%d ", __FILE__, __LINE__, errno); \
	perror(". Error:");\
	fflush(stdout);\
	abort();\
}
#define ASS(x) if (!(x)) DIE(x)
#define ASS1(x) ASS((x) != -1)
#define ASS0(x) ASS((x) == 0)

void * deadlocker(void *arg)
{
    int fd = (int)(ptrdiff_t)arg;
    for (;;) {
        ASS1( lockf(fd, F_LOCK, 1) );
        ASS1( lockf(fd, F_ULOCK, 1) );
    }
    return NULL;
}

int main(int argc, char * argv[])
{
    int fd1, fd2;
    ASS( argc >= 3 );
    ASS1( fd1 = creat(argv[1], 0660) );
    ASS1( fd2 = creat(argv[2], 0660) );
    void * thrv;
    pthread_t thr1, thr2;
    ASS0( pthread_create(&thr1, NULL, deadlocker, (void *)(ptrdiff_t)fd2) );
    ASS0( pthread_create(&thr2, NULL, deadlocker, (void *)(ptrdiff_t)fd1) );
    ASS0( pthread_join(thr1, &thrv) );
    ASS0( pthread_join(thr2, &thrv) );
    return 0;
}