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=-19.4 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, URIBL_BLOCKED,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 0066EC11F69 for ; Mon, 12 Jul 2021 08:14:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CCC6A6142F for ; Mon, 12 Jul 2021 08:14:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353464AbhGLIOx (ORCPT ); Mon, 12 Jul 2021 04:14:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:43856 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343683AbhGLH2q (ORCPT ); Mon, 12 Jul 2021 03:28:46 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CB99161370; Mon, 12 Jul 2021 07:24:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626074663; bh=gmheCfvythPcp/bQS7LLZEaWytqmQPx21ikpAMv9Qrs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mH7i9rGAKC72IW23oQLpPg6OiFjf5ruqLteBF7fzc+0aFScfrERToLyCKH1MBaJR8 rPRmsYEGl5+hUgenFQOfmOGVxzbCgYStZWeF+a5Z6kgeGKsH6zJbTPnaYCRqiweQcv lRMGaT4luLI72RRXOxKeUiBEhlrlH4l4anSGl4gM= 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 5.12 654/700] powerpc: Offline CPU in stop_this_cpu() Date: Mon, 12 Jul 2021 08:12:17 +0200 Message-Id: <20210712061045.434849846@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060924.797321836@linuxfoundation.org> References: <20210712060924.797321836@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 1d7daef1c3b6..216919de87d7 100644 --- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -619,6 +619,8 @@ 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(); @@ -634,6 +636,15 @@ 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