From owner-freebsd-current Wed Mar 10 11: 5:45 1999 Delivered-To: freebsd-current@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [209.157.86.2]) by hub.freebsd.org (Postfix) with ESMTP id 4E3B4151DD for ; Wed, 10 Mar 1999 11:05:31 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.3/8.9.1) id LAA57081; Wed, 10 Mar 1999 11:05:11 -0800 (PST) (envelope-from dillon) Date: Wed, 10 Mar 1999 11:05:11 -0800 (PST) From: Matthew Dillon Message-Id: <199903101905.LAA57081@apollo.backplane.com> To: Dag-Erling Smorgrav Cc: sthaug@nethelp.no, dcs@newsguy.com, Jos.Backus@nl.origin-it.com, dima@tejblum.dnttm.rssi.ru, perhaps@yes.no, freebsd-current@FreeBSD.ORG Subject: Re: panic: zone: entry not free References: <28892.921083219@verdi.nethelp.no> Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG :No, it is not - not in the general case, and not in the long term. I :was trying to point out that there may be extreme cases where an :otherwise harmless bug would cause a panic with invariants enabled. : :Matt claimed that invariants increase data safety, which I find :difficult to understand. : :DES There is no such thing as a harmless bug. If it's a bug, it needs to be fixed. Many 'harmless bugs' which are noted in source code come back to bite you later when some other programmer adds new code that uses a function in a legal but never-before-tested way. It is my considered opinion that one of the reasons why it has taken FreeBSD years to work out and fix serious bugs in the kernel is that there are simply not enough sanity checks being made in the kernel. The VM system is especially fragile in this regard, but most of the rest of the system has the same problem. For example, trying to block on a lockmgr lock inside an interrupt should result in an instantanious panic. But it doesn't. I can recall at least a dozen bugs that took months to locate because that sort of sanity check is not being made. It is *NOT* 'harmless', even if the occassional hit doesn't fry the system. -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message