Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754538AbYJBNQb (ORCPT ); Thu, 2 Oct 2008 09:16:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753611AbYJBNQW (ORCPT ); Thu, 2 Oct 2008 09:16:22 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:46191 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753604AbYJBNQV (ORCPT ); Thu, 2 Oct 2008 09:16:21 -0400 Date: Thu, 2 Oct 2008 09:16:19 -0400 (EDT) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: Ingo Molnar cc: Linus Torvalds , Peter Zijlstra , Jonathan Corbet , Mathieu Desnoyers , LKML , Thomas Gleixner , Andrew Morton , prasad@linux.vnet.ibm.com, "Frank Ch. Eigler" , David Wilder , hch@lst.de, Martin Bligh , Christoph Hellwig , Masami Hiramatsu , Steven Rostedt , Arnaldo Carvalho de Melo Subject: Re: [boot crash] Re: [PATCH] ring-buffer: fix build error In-Reply-To: <20081002093835.GA17699@elte.hu> Message-ID: References: <20080930092001.69849210@bike.lwn.net> <1222790072.24384.21.camel@twins> <20081002085030.GF26084@elte.hu> <20081002085145.GA3202@elte.hu> <20081002090517.GA8708@elte.hu> <20081002093835.GA17699@elte.hu> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1587 Lines: 47 On Thu, 2 Oct 2008, Ingo Molnar wrote: > [ 0.332002] Kernel panic - not syncing: Fatal exception > > full serial log and config attached. I'm excluding these latest commits > from tip/master for now: Thanks I'll take a look at this. > > 339ce9a: ring-buffer: fix build error > b6eeea4: ftrace: preempt disable over interrupt disable The above "preempt disable" is the most likely culprit. I'm trying to get towards an interrupt disabled free and lockless code path. But in doing so, one must be extra careful. This is why I'm taking baby steps towards this approach. Any little error in one of these steps, and you have race conditions biting you. The above replaces interrupt disables with preempt disables, uses the atomic data disable to protect against reentrancy. But this could also have opened up a bug that was not present with the interrupts disabled version. > 52abc82: ring_buffer: allocate buffer page pointer > da78331: ftrace: type cast filter+verifier > > i'm quite sure 52abc82 causes this problem. Hmm, that was a trivial patch. Perhaps the trivial ones are the ones that are most likely to be error prone. A developer will take much more care in developing a patch that is complex than something he sees as trivial ;-) -- Steve > > Another 64-bit testbox crashed too meanwhile. > > Ingo > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/