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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 43430C433E0 for ; Mon, 11 Jan 2021 17:12:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 02D7522B51 for ; Mon, 11 Jan 2021 17:12:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389362AbhAKRMW (ORCPT ); Mon, 11 Jan 2021 12:12:22 -0500 Received: from foss.arm.com ([217.140.110.172]:33212 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389238AbhAKRMU (ORCPT ); Mon, 11 Jan 2021 12:12:20 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1A3A011FB; Mon, 11 Jan 2021 09:11:35 -0800 (PST) Received: from e120877-lin.cambridge.arm.com (e120877-lin.cambridge.arm.com [10.1.194.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 444B33F70D; Mon, 11 Jan 2021 09:11:34 -0800 (PST) From: vincent.donnefort@arm.com To: peterz@infradead.org, tglx@linutronix.de, linux-kernel@vger.kernel.org Cc: valentin.schneider@arm.com, Vincent Donnefort Subject: [PATCH 2/4] cpu/hotplug: CPUHP_BRINGUP_CPU exception in fail injection Date: Mon, 11 Jan 2021 17:10:45 +0000 Message-Id: <1610385047-92151-3-git-send-email-vincent.donnefort@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1610385047-92151-1-git-send-email-vincent.donnefort@arm.com> References: <1610385047-92151-1-git-send-email-vincent.donnefort@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Vincent Donnefort The atomic states (between CPUHP_AP_IDLE_DEAD and CPUHP_AP_ONLINE) are triggered by the CPUHP_BRINGUP_CPU step. If the latter doesn't run, none of the atomic can. Hence, rollback is not possible after a hotunplug CPUHP_BRINGUP_CPU step failure and the "fail" interface shouldn't allow it. Moreover, the current CPUHP_BRINGUP_CPU teardown callback (finish_cpu()) cannot fail anyway. Signed-off-by: Vincent Donnefort --- kernel/cpu.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 9121edf..bcd7b2a 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2216,9 +2216,14 @@ static ssize_t write_cpuhp_fail(struct device *dev, return -EINVAL; /* - * Cannot fail STARTING/DYING callbacks. + * Cannot fail STARTING/DYING callbacks. Also, those callbacks are + * triggered by BRINGUP_CPU bringup callback. Therefore, the latter + * can't fail during hotunplug, as it would mean we have no way of + * rolling back the atomic states that have been previously teared + * down. */ - if (cpuhp_is_atomic_state(fail)) + if (cpuhp_is_atomic_state(fail) || + (fail == CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)) return -EINVAL; /* -- 2.7.4