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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 11C73C5DF61 for ; Thu, 7 Nov 2019 14:46:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D83B72187F for ; Thu, 7 Nov 2019 14:46:58 +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="kbemZYtz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729776AbfKGOq5 (ORCPT ); Thu, 7 Nov 2019 09:46:57 -0500 Received: from merlin.infradead.org ([205.233.59.134]:33462 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726033AbfKGOq5 (ORCPT ); Thu, 7 Nov 2019 09:46:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=/OrRskXnNuvYig/50XlPP6h0k/nysPrTGBFYIGLGuRs=; b=kbemZYtzK3JmELNafF32Lxmc1 gRMJufJLmNBt97FDGu3WqjwiEiBwab3dB2xk2Uq1dc/KhBRlA6F1nb9ykoeH+PxuvXVZV8IJ9Z2PR kCMyHADv8MmNISol/yEl4ObegVKtLsPlQ1OFf0HSplzPE6vjW58gCTflj6geND/b3XGGSFZoONxwt SGAnVg7AYeMBsSi7MFgeApAJIAWu8JKQBwE/XcYqegio3JYvzwqL0OWulqpZRke4vpgywuCBp8m6h YWUQ//DhKWRzq7FZyyGOmEgSgY/t3HQWRJoBddWF9vi69IWlNidinqPpqxCiBQeaZpxY6dSBrlkus ygLpUVp6A==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iSj3a-0008Ns-BU; Thu, 07 Nov 2019 14:46:42 +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 DBB85301747; Thu, 7 Nov 2019 15:45:34 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 2746420241336; Thu, 7 Nov 2019 15:46:39 +0100 (CET) Date: Thu, 7 Nov 2019 15:46:39 +0100 From: Peter Zijlstra To: Valentin Schneider Cc: kernel test robot , Aaron Lu , Phil Auld , Julien Desfossez , Nishanth Aravamudan , LKML , Linus Torvalds , lkp@01.org Subject: Re: [sched] 10e7071b2f: BUG:kernel_NULL_pointer_dereference,address Message-ID: <20191107144639.GB4114@hirez.programming.kicks-ass.net> References: <20191107090808.GW29418@shao2-debian> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 07, 2019 at 01:51:47PM +0000, Valentin Schneider wrote: > Using that, the fail is on: > > if (need_pull_dl_task(rq, prev)) { > > Which is most likely explained by the above call ending up doing a > > dl_prio(prev->prio); > > which doesn't play well with > > class->pick_next_task(rq, NULL, NULL); > > > Now, this is no longer an issue (I think) with the rest of Peter's series, > since the above deref is gone with > > 67692435c411 ("sched: Rework pick_next_task() slow-path") > > It would be interesting to know whether LKP found this on a mainline kernel > and bisected it down, or if it stumbled on this while bisecting something > else. That seems pausible indeed.