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 C0EE4C07E9B for ; Mon, 12 Jul 2021 07:15:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD38761477 for ; Mon, 12 Jul 2021 07:15:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243949AbhGLHRy (ORCPT ); Mon, 12 Jul 2021 03:17:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:53038 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239603AbhGLGw4 (ORCPT ); Mon, 12 Jul 2021 02:52:56 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8EFC3610A6; Mon, 12 Jul 2021 06:50:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626072608; bh=1hBnDIF+sduapjhfuvMGL5/eDR7r5UOLZyaaGtPZrs4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=H2PvCYC3bgX+ZMbC0mDKmYuymKd6RW2BGL+YtKX77E41LQTZ2wy5wyrylYF7p7DiP 60DxQsAYbL3PZ6HVDEhPSzJXK+FR8m4j2A/d3N5StOdqG2zmUMY0NjWgRq7lASYw46 2pNIm4qEza5sOHKr5Mf3xrb4NyiFwys7BLXBpQRA= 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 5.10 553/593] powerpc: Offline CPU in stop_this_cpu() Date: Mon, 12 Jul 2021 08:11:53 +0200 Message-Id: <20210712060955.248665070@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060843.180606720@linuxfoundation.org> References: <20210712060843.180606720@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 0760230be56f..26a028a9233a 100644 --- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -600,6 +600,8 @@ 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(); @@ -615,6 +617,15 @@ 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