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,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 0D770C433ED for ; Mon, 10 May 2021 15:11:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D5E776101A for ; Mon, 10 May 2021 15:11:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234733AbhEJPM7 (ORCPT ); Mon, 10 May 2021 11:12:59 -0400 Received: from foss.arm.com ([217.140.110.172]:60738 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233157AbhEJPMZ (ORCPT ); Mon, 10 May 2021 11:12:25 -0400 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 772BC1691; Mon, 10 May 2021 08:11:20 -0700 (PDT) Received: from e113632-lin.cambridge.arm.com (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 5BF773F719; Mon, 10 May 2021 08:11:19 -0700 (PDT) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: Yejune Deng , mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de, bristot@redhat.com Subject: [PATCH 2/2] lib/smp_processor_id: Use is_percpu_thread() instead of nr_cpus_allowed Date: Mon, 10 May 2021 16:10:24 +0100 Message-Id: <20210510151024.2448573-3-valentin.schneider@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210510151024.2448573-1-valentin.schneider@arm.com> References: <20210510151024.2448573-1-valentin.schneider@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yejune Deng is_percpu_thread() more elegantly handles SMP vs UP, and further checks the presence of PF_NO_SETAFFINITY. This lets us catch cases where check_preemption_disabled() can race with a concurrent sched_setaffinity(). Signed-off-by: Yejune Deng [Amended changelog] Signed-off-by: Valentin Schneider --- lib/smp_processor_id.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/lib/smp_processor_id.c b/lib/smp_processor_id.c index 1c1dbd300325..046ac6297c78 100644 --- a/lib/smp_processor_id.c +++ b/lib/smp_processor_id.c @@ -19,11 +19,7 @@ unsigned int check_preemption_disabled(const char *what1, const char *what2) if (irqs_disabled()) goto out; - /* - * Kernel threads bound to a single CPU can safely use - * smp_processor_id(): - */ - if (current->nr_cpus_allowed == 1) + if (is_percpu_thread()) goto out; #ifdef CONFIG_SMP -- 2.25.1