From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 305DFC433E0 for ; Fri, 5 Jun 2020 10:56:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0BCDE206E6 for ; Fri, 5 Jun 2020 10:56:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="J5ozC2eX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726937AbgFEK4e (ORCPT ); Fri, 5 Jun 2020 06:56:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45138 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726918AbgFEK4e (ORCPT ); Fri, 5 Jun 2020 06:56:34 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ED333C08C5C2 for ; Fri, 5 Jun 2020 03:56:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=saGaZrcjpuLsokLkuqJY11c916jNr+yTKHM09OZCpIc=; b=J5ozC2eXJq+fpphcd4SqmfXiJz vBzmZyc7ZssHqW2l0FCvAOWyq+6cbPhGK0DZjGLrIf4ErqGZoStVRFt3E7WmxNyby66uGpWuMnSzv HCi5pXg6ko573as95hZ3EUWvUkjhT7svfA7OPpax2FbE8llrGbxrEXKzXZZzZUApJr3Zk/A6t2a5p cFvS6CCexzuWvt2WMwD3MniDTPFbwjaPyE4ORWFn4sJcGAZ71op6mlAyMtdNa2rKgc3wfkTjG/OQ4 dK9xBTXfqd+NzPjkv1ad70OtR++h1LT+GIaqUkV3qYkPTtclCKDS9v0rBVYWMHXkuzvo0Y8HdbGw1 ZSiSjfNg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jhA1I-0000u5-Ny; Fri, 05 Jun 2020 10:56:18 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id DBEE230280D; Fri, 5 Jun 2020 12:56:14 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A062121A74B27; Fri, 5 Jun 2020 12:56:14 +0200 (CEST) Date: Fri, 5 Jun 2020 12:56:14 +0200 From: Peter Zijlstra To: "Paul E. McKenney" Cc: mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: Re: BUG: kernel NULL pointer dereference from check_preempt_wakeup() Message-ID: <20200605105614.GC2948@hirez.programming.kicks-ass.net> References: <20200604225445.GA32319@paulmck-ThinkPad-P72> <20200605103859.GI3976@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200605103859.GI3976@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 05, 2020 at 12:38:59PM +0200, Peter Zijlstra wrote: > On Thu, Jun 04, 2020 at 03:54:45PM -0700, Paul E. McKenney wrote: > > Hello! > > > > I get the splat below at a rate of roughly two per thirty hours when > > running rcutorture scenario TREE03 on x86 at the June 3rd mainline commit: > > > > cb8e59cc8720 ("Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next") > > > > Running 140 hours of this same scenario at the following June 2nd mainline > > commit shows no errors: > > > > d9afbb350990 ("Merge branch 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security") > > > > I have started a bisection, but it is likely to take several days to > > complete. I am looking at ways of speeding this up, but in the meantime, > > I figured that I should check to see if others are also encountering this. > > > > Thoughts? > > I think this shows there's a boo-boo with the IPI patches. I've not > managed to reproduce, but I'll give them another hard look. > > Would you have a .config for me? My compiler's check_preempt_wakeup > isn't anywhere near 0x180 bytes long. I'm thiknig you have > instrumentation enabled, KCSAN? n/m, I was looking at the wrong function.. let me go puzzle.