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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 320B6C433E0 for ; Thu, 14 May 2020 13:54:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0393620671 for ; Thu, 14 May 2020 13:54:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589464444; bh=bNrG9XA/HjyOs+0yCswb5zYOyQkr7H9bUyY9HpZXdFs=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=nupBtOz1uqBZxqJv0iVrtN1KITq6iCy/SNekE8+lQ1pz5N0dgzKU3cc8Xfxihmefv dTSHXXGWm1uh2lLNFiBcBGFcFmDnUEYruct/ABhIrHJjHVMsFVPS72CNWNfVITkPR4 Ux7pQP3/Fsn8il/j7uz5NyC4qYU+N+lRX0FIi+GE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726117AbgENNyD (ORCPT ); Thu, 14 May 2020 09:54:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:47250 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726073AbgENNyD (ORCPT ); Thu, 14 May 2020 09:54:03 -0400 Received: from paulmck-ThinkPad-P72.home (unknown [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 97198205CB; Thu, 14 May 2020 13:54:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589464442; bh=bNrG9XA/HjyOs+0yCswb5zYOyQkr7H9bUyY9HpZXdFs=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=QWJYt4wEUS1rFbebQVlFjN3m/eKsEr/xBfs4ECKjTfE9k0eMwRGO9qWMyqUaRxlLG mU2TXve7ph1ssgyQpd6zlo8pGFNEOe2np32uwSi+akKIG7pSOB1AwVI3Obmi+qiRK5 DtHJmMgY1HOkFUyDjEJaduNRfKNFlfnmFH+UeeO4= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 1F57C35229C5; Thu, 14 May 2020 06:54:02 -0700 (PDT) Date: Thu, 14 May 2020 06:54:02 -0700 From: "Paul E. McKenney" To: Qian Cai Cc: Stephen Rothwell , Linux Next Mailing List , Linux Kernel Mailing List , Madhuparna Bhowmik , Amol Grover , Dmitry Vyukov Subject: Re: Default enable RCU list lockdep debugging with PROVE_RCU Message-ID: <20200514135402.GI2869@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200514222535.259cb69e@canb.auug.org.au> <20200514133328.GG2869@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-next-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-next@vger.kernel.org On Thu, May 14, 2020 at 09:44:28AM -0400, Qian Cai wrote: > > > > On May 14, 2020, at 9:33 AM, Paul E. McKenney wrote: > > > > On Thu, May 14, 2020 at 08:31:13AM -0400, Qian Cai wrote: > >> > >> > >>> On May 14, 2020, at 8:25 AM, Stephen Rothwell wrote: > >>> > >>> Hi Paul, > >>> > >>> This patch in the rcu tree > >>> > >>> d13fee049fa8 ("Default enable RCU list lockdep debugging with PROVE_RCU") > >>> > >>> is causing whack-a-mole in the syzbot testing of linux-next. Because > >>> they always do a debug build of linux-next, no testing is getting done. :-( > >>> > >>> Can we find another way to find all the bugs that are being discovered > >>> (very slowly)? > >> > >> Alternatively, could syzbot to use PROVE_RCU=n temporarily because it can’t keep up with it? I personally found PROVE_RCU_LIST=y is still useful for my linux-next testing, and don’t want to lose that coverage overnight. > > > > The problem is that PROVE_RCU is exactly PROVE_LOCKING, and asking people > > to test without PROVE_LOCKING is a no-go in my opinion. But of course > > on the other hand if there is no testing of RCU list lockdep debugging, > > those issues will never be found, let alone fixed. > > > > One approach would be to do as Stephen asks (either remove d13fee049fa8 > > or pull it out of -next) and have testers force-enable the RCU list > > lockdep debugging. > > > > Would that work for you? > > Alternatively, how about having > > PROVE_RCU_LIST=n if DEBUG_AID_FOR_SYZBOT > > since it is only syzbot can’t keep up with it? Sound good to me, assuming that this works for the syzkaller guys. Or could there be a "select PROVE_RCU_LIST" for the people who would like to test it. Alternatively, if we revert d13fee049fa8 from -next, I could provide you a script that updates your .config to set both RCU_EXPERT and PROVE_RCU_LIST. There are a lot of ways to appraoch this. So what would work best for everyone? Thanx, Paul