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=-10.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 65DE0C4320E for ; Mon, 2 Aug 2021 06:37:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4F00660F39 for ; Mon, 2 Aug 2021 06:37:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229734AbhHBGiG (ORCPT ); Mon, 2 Aug 2021 02:38:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46332 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232240AbhHBGiF (ORCPT ); Mon, 2 Aug 2021 02:38:05 -0400 Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8E369C0613D5 for ; Sun, 1 Aug 2021 23:37:56 -0700 (PDT) Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4GdSxG32lFz9sT6; Mon, 2 Aug 2021 16:37:53 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ellerman.id.au; s=201909; t=1627886274; bh=0uXfwbhBCmX/Vg3rWzcrO7cxScT07wbJRsldPrQjcJg=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=UlyAEEuqpUr7HyNxGmr/t+o9RMm53ShS+XC28yL19BQiVGDFZzrBOz4fJJQseGlzi 4Kq6ZJ+SfaTnw7QipHwL+/CR/4x2CN819spyjvnNXy325llTLEu4EKc4dgXy1XYjnO UByIo8RBqrAiGjfX+JwnmxFKvkwleB17R+3av8LMjSxEDhtmremWL1NEbQ18IYzaYM C3LqTv7dzTJoomE+6DR+qBHIunwvb2hy7knTYawsTa5WAP7fBQTxekQSn9uqw69R8V 0AFgwH4pvkuoPv2+6/s9wz19J+Rx7EUwtxDRC76NIrCHqETnh1sFb4hrVrQZAREihy Fuw/vbYGtly9g== From: Michael Ellerman To: =?utf-8?Q?C=C3=A9dric?= Le Goater , linuxppc-dev@lists.ozlabs.org Cc: =?utf-8?Q?C=C3=A9dric?= Le Goater , stable@vger.kernel.org, Geetika Moolchandani , Srikar Dronamraju Subject: Re: [PATCH] powerpc/xive: Do not skip CPU-less nodes when creating the IPIs In-Reply-To: <20210629131542.743888-1-clg@kaod.org> References: <20210629131542.743888-1-clg@kaod.org> Date: Mon, 02 Aug 2021 16:37:53 +1000 Message-ID: <87a6m0l5by.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org C=C3=A9dric Le Goater writes: > On PowerVM, CPU-less nodes can be populated with hot-plugged CPUs at > runtime. Today, the IPI is not created for such nodes, and hot-plugged > CPUs use a bogus IPI, which leads to soft lockups. > > We could create the node IPI on demand but it is a bit complex because > this code would be called under bringup_up() and some IRQ locking is > being done. The simplest solution is to create the IPIs for all nodes > at startup. > > Fixes: 7dcc37b3eff9 ("powerpc/xive: Map one IPI interrupt per node") > Cc: stable@vger.kernel.org # v5.13 > Reported-by: Geetika Moolchandani > Cc: Srikar Dronamraju > Signed-off-by: C=C3=A9dric Le Goater > --- > > This patch breaks old versions of irqbalance (<=3D v1.4). Possible nodes > are collected from /sys/devices/system/node/ but CPU-less nodes are > not listed there. When interrupts are scanned, the link representing > the node structure is NULL and segfault occurs. Breaking userspace is usually frowned upon, even if it is irqbalance. If CPU-less nodes appeared in /sys/devices/system/node would that fix it? Could we do that or is that not possible for other reasons? > Version 1.7 seems immune.=20 Which was released in August 2020. Looks like some distros still ship 1.6, I take it you're not sure if that is broken or not. cheers