From owner-freebsd-arch@FreeBSD.ORG Fri Nov 16 01:48:01 2012 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 509754AB for ; Fri, 16 Nov 2012 01:48:01 +0000 (UTC) (envelope-from postmaster@mailpod.hostingplatform.com) Received: from atl4mhob06.myregisteredsite.com (atl4mhob06.myregisteredsite.com [209.17.115.44]) by mx1.freebsd.org (Postfix) with ESMTP id E195E8FC13 for ; Fri, 16 Nov 2012 01:48:00 +0000 (UTC) Received: from mailpod1.hostingplatform.com (mailpod1.networksolutionsemail.com [206.188.198.65]) by atl4mhob06.myregisteredsite.com (8.14.4/8.14.4) with ESMTP id qAG1m0ND018566 for ; Thu, 15 Nov 2012 20:48:00 -0500 Received: (qmail 12667 invoked by uid 0); 16 Nov 2012 01:48:00 -0000 Received: (qmail 32120 invoked by uid 0); 15 Nov 2012 17:57:04 -0000 Received: from unknown (HELO atl4mhib42.myregisteredsite.com) (209) by 0 with SMTP; 15 Nov 2012 17:57:04 -0000 Received: from mx2.freebsd.org (mx2.freebsd.org [69.147.83.53]) by atl4mhib42.myregisteredsite.com (8.14.4/8.14.4) with ESMTP id qAFHv1nv032376 for ; Thu, 15 Nov 2012 12:57:01 -0500 Received: from hub.freebsd.org (hub.FreeBSD.org [8.8.178.136]) by mx2.freebsd.org (Postfix) with ESMTP id 4B6AB3B5D7B; Thu, 15 Nov 2012 17:56:37 +0000 (UTC) Received: from hub.FreeBSD.org (hub.FreeBSD.org [8.8.178.136]) by hub.freebsd.org (Postfix) with ESMTP id 686CA3DC; Thu, 15 Nov 2012 17:56:37 +0000 (UTC) (envelope-from owner-freebsd-hackers@freebsd.org) Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id F3CBF29D for ; Thu, 15 Nov 2012 17:56:23 +0000 (UTC) (envelope-from imp@bsdimp.com) Received: from mail-oa0-f54.google.com (mail-oa0-f54.google.com [209.85.219.54]) by mx1.freebsd.org (Postfix) with ESMTP id A537B8FC14 for ; Thu, 15 Nov 2012 17:56:23 +0000 (UTC) Received: by mail-oa0-f54.google.com with SMTP id n9so2409833oag.13 for ; Thu, 15 Nov 2012 09:56:22 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=sender:subject:mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to:x-mailer :x-gm-message-state; bh=Q8SFrS7WLIfT9llpZ/gg0GR2wFSWpUMEED98gONNncI=; b=L4oHlgxKV/uYmCGap7vFNxxc9yj8pf1wPMQ/E0rFSoRPkAlCpEdjYDnGRjSqucEoFr OgwrlB9HXn33zD+MgtvJsuI677U+uKobP2tUBRFI3x3EwUf3jJmbEpl8TYQPJjN5PyBr P0M8vt1Uh+eCa3sZ9BIpumOictAkpy2Q6W0mig1f32IzN48xguZeEnMmvlNyw6zeOA0O JZJnyELCb1zG3ODmzOiLHAWbrxXYeYFWlwAJfXQ3auwSB1NmnlabHofQxk8H1gbsSxes OCJIKNa+UIvG8a/M9dKJW6WtVDt1oMz/hwu34HS75q98M7yd6b5b0RI92kQBXwgNd4Gh 1hvQ== Received: by 10.60.10.133 with SMTP id i5mr1574894oeb.11.1353002182724; Thu, 15 Nov 2012 09:56:22 -0800 (PST) Received: from [10.30.101.53] ([209.117.142.2]) by mx.google.com with ESMTPS id m8sm12902611oeb.3.2012.11.15.09.56.20 (version=TLSv1/SSLv3 cipher=OTHER); Thu, 15 Nov 2012 09:56:21 -0800 (PST) Subject: Re: [RFQ] make witness panic an option Mime-Version: 1.0 (Apple Message framework v1085) From: Warner Losh In-Reply-To: Date: Thu, 15 Nov 2012 10:56:17 -0700 Message-Id: <47374EC3-5022-49AC-A17E-7F234A88B5C6@bsdimp.com> References: <1353001175.1217.153.camel@revolution.hippie.lan> To: attilio@FreeBSD.org X-Mailer: Apple Mail (2.1085) X-Gm-Message-State: ALoCoQmSwLPuMypES8ja2cHJ1nzIsffgVbdDtBnp+r8cH7mCpLt82C6AKIRmmKwU8cbD7QZF/Rnh X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: owner-freebsd-hackers@freebsd.org Sender: owner-freebsd-hackers@freebsd.org X-SpamScore: 0 X-MailHub-Apparently-To: mjm@michaelmeltzer.com X-MailHub-Forwarded: Yes Cc: Ian Lepore , Adrian Chadd , freebsd-hackers@freebsd.org, freebsd-arch@freebsd.org X-BeenThere: freebsd-arch@freebsd.org List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 16 Nov 2012 01:48:01 -0000 On Nov 15, 2012, at 10:47 AM, Attilio Rao wrote: > On 11/15/12, Ian Lepore wrote: >> On Wed, 2012-11-14 at 22:15 -0800, Adrian Chadd wrote: >>> Hi all, >>> >>> When debugging and writing wireless drivers/stack code, I like to >>> sprinkle lots of locking assertions everywhere. However, this does >>> cause things to panic quite often during active development. >>> >>> This patch (against stable/9) makes the actual panic itself >>> configurable. It still prints the message regardless. >>> >>> This has allowed me to sprinkle more locking assertions everywhere to >>> investigate whether particular paths have been hit or not. I don't >>> necessarily want those to panic the kernel. >>> >>> I'd like everyone to consider this for FreeBSD-HEAD. >>> >>> Thanks! >> >> I strongly support this, because I'm tired of having to hack it in by >> hand every time I need it. >> >> You can't boot an arm platform right now (on freebsd 8, 9, or 10) >> without a LOR very early in the boot. Once you get past that, 2 or 3 >> device drivers I use panic way before we even get to mounting root. >> Those panics can clearly be ignored, because we've been shipping >> products for years based on this code. (It's on my to-do list to fix >> them, but more pressing problems are higher on the list.) > > This is a ridicolous motivation. > What are the panics in question? Why they are not fixed yet? > Without WITNESS_KDB you should not panic even in cases where WITNESS > yells. So if you do, it means there is a more subdole breakage going > on here. > > Do you really think that an abusable mechanism will help here rather > than fixing the actual problems? > >> When a new problem crops up that isn't harmless, it totally sucks that I >> can't just turn on witness without first hacking the code to make the >> known problems non-panicky. > > I really don't understand what are these "harmless problems" here. > I just know one and it is between the dirhash lock and the bufwait > lock for UFS, which is carefully documented in the code comments. All > the others cases haven't been analyzed deeply enough to quantify them > as "harmless". > > Can you please make real examples? It sounds like he's more worried about introducing LoRs into his wireless code. They are harmless, for him, and he can fix them by reloading the driver. They are only harmful if he loses a race. Warner _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org"