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=-20.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 A92F6C6377D for ; Mon, 19 Jul 2021 16:21:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8F651613F9 for ; Mon, 19 Jul 2021 16:21:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346736AbhGSPjB (ORCPT ); Mon, 19 Jul 2021 11:39:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:53810 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343855AbhGSO7X (ORCPT ); Mon, 19 Jul 2021 10:59:23 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id E183A61353; Mon, 19 Jul 2021 15:37:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626709055; bh=5MbsnozhPTJL9h5KtJUwuo/wLMDLSOJeNoVttIPL/bE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QJDuXDfmQv9QcbT89scIAo4YwZFERmfUcZQSwdmAH613QlVcFAptL+aAIJ4KRDfuV DpkaXQv2wquPP0M/Fw/MiM0bkfTD6uaXrSOa5XPRVNAnxLjkRFWq56YemIvlSTBqQp FizMOhiVUbge8O12/EsLVVmoKWEoCTLHSylNahvU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Nicholas Piggin , Michael Ellerman , Sasha Levin Subject: [PATCH 4.19 218/421] powerpc: Offline CPU in stop_this_cpu() Date: Mon, 19 Jul 2021 16:50:29 +0200 Message-Id: <20210719144953.897089678@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210719144946.310399455@linuxfoundation.org> References: <20210719144946.310399455@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Nicholas Piggin [ Upstream commit bab26238bbd44d5a4687c0a64fd2c7f2755ea937 ] printk_safe_flush_on_panic() has special lock breaking code for the case where we panic()ed with the console lock held. It relies on panic IPI causing other CPUs to mark themselves offline. Do as most other architectures do. This effectively reverts commit de6e5d38417e ("powerpc: smp_send_stop do not offline stopped CPUs"), unfortunately it may result in some false positive warnings, but the alternative is more situations where we can crash without getting messages out. Fixes: de6e5d38417e ("powerpc: smp_send_stop do not offline stopped CPUs") Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210623041245.865134-1-npiggin@gmail.com Signed-off-by: Sasha Levin --- arch/powerpc/kernel/smp.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c index a9ec4467705c..14adfeacfa46 100644 --- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -570,6 +570,8 @@ static void nmi_stop_this_cpu(struct pt_regs *regs) /* * IRQs are already hard disabled by the smp_handle_nmi_ipi. */ + set_cpu_online(smp_processor_id(), false); + spin_begin(); while (1) spin_cpu_relax(); @@ -585,6 +587,15 @@ void smp_send_stop(void) static void stop_this_cpu(void *dummy) { hard_irq_disable(); + + /* + * Offlining CPUs in stop_this_cpu can result in scheduler warnings, + * (see commit de6e5d38417e), but printk_safe_flush_on_panic() wants + * to know other CPUs are offline before it breaks locks to flush + * printk buffers, in case we panic()ed while holding the lock. + */ + set_cpu_online(smp_processor_id(), false); + spin_begin(); while (1) spin_cpu_relax(); -- 2.30.2