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 72536C433DB for ; Tue, 16 Feb 2021 10:36:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2C40064DF0 for ; Tue, 16 Feb 2021 10:36:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230055AbhBPKgy (ORCPT ); Tue, 16 Feb 2021 05:36:54 -0500 Received: from foss.arm.com ([217.140.110.172]:60208 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229924AbhBPKgJ (ORCPT ); Tue, 16 Feb 2021 05:36:09 -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 01BF9ED1; Tue, 16 Feb 2021 02:35:24 -0800 (PST) Received: from e124901.arm.com (unknown [10.57.6.158]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id C54173F73B; Tue, 16 Feb 2021 02:35:22 -0800 (PST) From: vincent.donnefort@arm.com To: peterz@infradead.org, tglx@linutronix.de Cc: linux-kernel@vger.kernel.org, valentin.schneider@arm.com, Vincent Donnefort Subject: [PATCH v2 2/3] cpu/hotplug: CPUHP_BRINGUP_CPU failure exception Date: Tue, 16 Feb 2021 10:35:05 +0000 Message-Id: <20210216103506.416286-3-vincent.donnefort@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210216103506.416286-1-vincent.donnefort@arm.com> References: <20210216103506.416286-1-vincent.donnefort@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 fails, no atomic state can be rolled back. DEAD callbacks too can't fail and disallow recovery. As a consequence, during hotunplug, the fail injection interface should prohibit all states from CPUHP_BRINGUP_CPU to CPUHP_ONLINE. Signed-off-by: Vincent Donnefort diff --git a/kernel/cpu.c b/kernel/cpu.c index 093f96fb0824..d44877095b8c 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1038,9 +1038,13 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen, * to do the further cleanups. */ ret = cpuhp_down_callbacks(cpu, st, target); - if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) { - cpuhp_reset_state(st, prev_state); - __cpuhp_kick_ap(st); + if (ret && st->state < prev_state) { + if (st->state == CPUHP_TEARDOWN_CPU) { + cpuhp_reset_state(st, prev_state); + __cpuhp_kick_ap(st); + } else { + WARN(1, "DEAD callback error for CPU%d", cpu); + } } out: @@ -2214,6 +2218,15 @@ static ssize_t write_cpuhp_fail(struct device *dev, if (cpuhp_is_atomic_state(fail)) return -EINVAL; + /* + * DEAD callbacks cannot fail... + * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter + * triggering STARTING callbacks, a failure in this state would + * hinder rollback. + */ + if (fail <= CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU) + return -EINVAL; + /* * Cannot fail anything that doesn't have callbacks. */ -- 2.25.1