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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 88689C4363A for ; Mon, 5 Oct 2020 07:52:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C7EA20756 for ; Mon, 5 Oct 2020 07:52:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Ad0lv/gp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725906AbgJEHwP (ORCPT ); Mon, 5 Oct 2020 03:52:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34246 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725870AbgJEHwO (ORCPT ); Mon, 5 Oct 2020 03:52:14 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6C546C0613CE for ; Mon, 5 Oct 2020 00:52:14 -0700 (PDT) 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; bh=kQD4/+GHLTI2vl6Qa3BGsZpfghTWh9K/7MHOnahIPWA=; b=Ad0lv/gpVg4Q5ghNTeTJnwcMph XSOY85e/Gf4ghk4fZkPyMp3gXy33r1BlMdd/TI5VZksBqJs/UsbpKxjwsVPUT3rWXti/QNC4x7Qly 2woyuhahSEHLyaBNYueDAXmA0u1AXPsLVV3uD1mF1Of8keTOyT1FapQx3S/7sfBGlwe/s+bcQbIAI vzg+EQNAwpj3O71M0cq3MwmyNAElMFEdMfuiGFbOYehcCEr0jR/gzn0kKMNa39F1vUAC6W/Nxw9Un QndhGxJvPKwV4xZA2trymT0abd6MFIvhtSyFFj3TbL1/gbl/DZ3gD21fu5RSbBQiXgo9R6KJGaK7a HpcBNj5g==; 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 1kPLI0-0001zV-My; Mon, 05 Oct 2020 07:52:08 +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 6059B3013E5; Mon, 5 Oct 2020 09:52:06 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 1C2D122BBB6D7; Mon, 5 Oct 2020 09:52:06 +0200 (CEST) Date: Mon, 5 Oct 2020 09:52:06 +0200 From: Peter Zijlstra To: Steven Rostedt Cc: Thomas Gleixner , "Paul E. McKenney" , LKML , svens@linux.ibm.com Subject: Re: [WARNING] kernel/rcu/tree.c:1058 rcu_irq_enter+0x15/0x20 Message-ID: <20201005075206.GI2651@hirez.programming.kicks-ass.net> References: <20200917131647.2b55ebb1@gandalf.local.home> <20200930181323.GF2628@hirez.programming.kicks-ass.net> <20201002135644.7903d0e5@gandalf.local.home> <20201002181313.GM29142@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201002181313.GM29142@worktop.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 02, 2020 at 08:13:13PM +0200, Peter Zijlstra wrote: > > checks within the irq disabling to get rid of the using cpu pointers within > > preemptable code warnings > > Ah, I think I lost a s/__this_cpu_read/raw_cpu_read/ somewhere. The > thing is, if we're preemptible/migratable it will be 0 on both CPUs and > it doesn't matter which 0 we read. If it is !0, IRQs will be disabled > and we can't get migrated. Aargh, this isn't in fact correct, and that means I have to revert: fddf9055a60d ("lockdep: Use raw_cpu_*() for per-cpu variables") The trouble is that on a bunch of architectures we can read the other CPUs variable from the new CPU, long after the old CPU has continued executing things. So this really needs to be this_cpu_read(). Luckily Sven has already fixed s390, but let me go audit all the other archs.