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=-3.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=no 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 BE3DFC352A4 for ; Wed, 12 Feb 2020 21:14:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8FB07217F4 for ; Wed, 12 Feb 2020 21:14:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="mrMcE+oE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729256AbgBLVO0 (ORCPT ); Wed, 12 Feb 2020 16:14:26 -0500 Received: from merlin.infradead.org ([205.233.59.134]:33530 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729107AbgBLVOT (ORCPT ); Wed, 12 Feb 2020 16:14:19 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-Id:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=mocOxZQUeqTQQ8yUjNc0DjmC3mFU9HxodacHaxasgBg=; b=mrMcE+oEiR7AV3tvqz+nagCfXK vZ92EkbvuT8cXWn1bQiE89yk8R3NYhjZ+9Qheg0zZbWcLBbuFY7t3KrktePTvJJgkxMz+ovBpYEfe Y4I0dQAYEwfJyAfdsnpKViQjv/YLaTUo2HWc0W3Fxz6T8t7xY/EtoOZcvg8NShXbRvSsNibsTEqUL SSM97GW1Gs4wHn44HLhH5WYXCjsr5WR1pTWepn5f0BOOnV9aadDR7IasMyZWbCdcNrfeYTbBXmqGR fZfnx/63uTOpFV1Qw4nsMwQ6SR512lABJ8Iko+VKTizDZGJLpU37qaDCLS+EtJjqyTjv53lYlMGf7 3C1fM8qg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1j1zKM-0002Kx-3D; Wed, 12 Feb 2020 21:13:46 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id C1BC8306E5C; Wed, 12 Feb 2020 22:11:52 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 85972203A89A9; Wed, 12 Feb 2020 22:13:41 +0100 (CET) Message-Id: <20200212210750.084959585@infradead.org> User-Agent: quilt/0.65 Date: Wed, 12 Feb 2020 22:01:44 +0100 From: Peter Zijlstra To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, rostedt@goodmis.org Cc: peterz@infradead.org, mingo@kernel.org, joel@joelfernandes.org, gregkh@linuxfoundation.org, gustavo@embeddedor.com, tglx@linutronix.de, paulmck@kernel.org, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com Subject: [PATCH v2 5/9] x86,tracing: Add comments to do_nmi() References: <20200212210139.382424693@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add a few comments to do_nmi() as a result of the audit. Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/kernel/nmi.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) --- a/arch/x86/kernel/nmi.c +++ b/arch/x86/kernel/nmi.c @@ -529,11 +529,14 @@ do_nmi(struct pt_regs *regs, long error_ * continue to use the NMI stack. */ if (unlikely(is_debug_stack(regs->sp))) { - debug_stack_set_zero(); + debug_stack_set_zero(); /* notrace due to Makefile */ this_cpu_write(update_debug_stack, 1); } #endif + /* + * It is important that no tracing happens before nmi_enter()! + */ nmi_enter(); inc_irq_stat(__nmi_count); @@ -542,10 +545,13 @@ do_nmi(struct pt_regs *regs, long error_ default_do_nmi(regs); nmi_exit(); + /* + * No tracing after nmi_exit()! + */ #ifdef CONFIG_X86_64 if (unlikely(this_cpu_read(update_debug_stack))) { - debug_stack_reset(); + debug_stack_reset(); /* notrace due to Makefile */ this_cpu_write(update_debug_stack, 0); } #endif