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 588C5C433E9 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 21C3F22B30 for ; Mon, 11 Jan 2021 17:12:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389378AbhAKRM0 (ORCPT ); Mon, 11 Jan 2021 12:12:26 -0500 Received: from foss.arm.com ([217.140.110.172]:33228 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389352AbhAKRMW (ORCPT ); Mon, 11 Jan 2021 12:12:22 -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 11A7613A1; Mon, 11 Jan 2021 09:11:37 -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 47FED3F73C; Mon, 11 Jan 2021 09:11:36 -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 4/4] cpu/hotplug: Fix CPU down rollback Date: Mon, 11 Jan 2021 17:10:47 +0000 Message-Id: <1610385047-92151-5-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 After the AP brought itself down to CPUHP_TEARDOWN_CPU, the BP will finish the job. The steps left are as followed: +--------------------+ | CPUHP_TEARDOWN_CPU | -> If fails state is CPUHP_TEARDOWN_CPU +--------------------+ | ATOMIC STATES | -> Cannot Fail +--------------------+ | CPUHP_BRINGUP_CPU | -> Cannot fail +--------------------+ | ... | | ... | -> Can fail and rollback | CPUHP_OFFLINE | +--------------------+ There are, in case of failure two possibilities: 1. Failure in CPUHP_TEARDOWN_CPU, then st->state will still be CPUHP_TEARDOWN_CPU 2. Failure between CPUHP_OFFLINE and CPUHP_BRINGUP_CPU. For 2. The rollback will always run in the CPUHP_BRINGUP_CPU bringup callback (bringup_cpu()) which kicks the AP back on. The latter will then end-up setting st->state to CPUHP_AP_ONLINE_IDLE. Checking for CPUHP_AP_ONLINE_IDLE allows then to rollback in all cases. Signed-off-by: Vincent Donnefort --- kernel/cpu.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index aebec3a..8b3f84e 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1078,7 +1078,14 @@ 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) { + if (ret && (st->state == CPUHP_AP_ONLINE_IDLE || + st->state == CPUHP_TEARDOWN_CPU) && + st->state < prev_state) { + /* + * After an error the state can be either: + * - CPUHP_TEARDOWN_CPU if this step failed. + * - CPUHP_AP_ONLINE_IDLE if any other failed. + */ cpuhp_reset_state(st, prev_state); __cpuhp_kick_ap(st); } -- 2.7.4