#include <stdio.h>

union {
	struct {
		unsigned char val;
		unsigned char flag;
	};
	unsigned short lock;
} l = { 0,0 };

int main(int argc, char **argv)
{
	int i;
	{
	    {

			for (i = 0; i < 100000000; i++) {
				unsigned short inc = 2;
				if (l.val >= (0x100 - 2))
					inc += -1 << 8;
				asm volatile("lock; xadd %1,%0" : "+m" (l.lock), "+r" (inc) : );
				if (inc & 0x100)
					break;
				asm volatile("" : : : "memory");
			}
			l.flag = 1;
		}
	}
	return 0;
}