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=-3.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 0A2CAC34047 for ; Wed, 19 Feb 2020 15:15:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D302724671 for ; Wed, 19 Feb 2020 15:15:41 +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="GaQZ2+he" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727827AbgBSPPk (ORCPT ); Wed, 19 Feb 2020 10:15:40 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:36000 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727636AbgBSPO1 (ORCPT ); Wed, 19 Feb 2020 10:14:27 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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=GaQZ2+heDUJP0fGQR2vqWg7Xrk z3cN44YljnueYMO9GiZ6R0YMafompFYV7GECXJsoXxIThvpBV3t0CIAYYT8ur+SsPshSalYXEX4+N JnrdfQMRzQvkymXieISEV6qcb1RoUgVMQF6NPInatRFaorwkJGPsU3KwbvPV+3Z1NB10gkx7gFYx5 qgxGuP+zkDMcvyWarnqd8alHF3QCXZlvGOT/Fp6e1NX5SS0Kd3UUUEwoEG4paUld3Er9533wrYCNs 8ofM25Z8uQ9QyHwmS+NYCgsGwGh0EELMmy3ggAh6y5jh2GsaV/E9Owcjy+zGqgQMatsjd+js81DBb JPZaqFaA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1j4R39-000110-6b; Wed, 19 Feb 2020 15:14:07 +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 F093E3077E6; Wed, 19 Feb 2020 16:12:11 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 873D12B17062B; Wed, 19 Feb 2020 16:14:03 +0100 (CET) Message-Id: <20200219150744.945913022@infradead.org> User-Agent: quilt/0.65 Date: Wed, 19 Feb 2020 15:47:34 +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, luto@kernel.org, tony.luck@intel.com, frederic@kernel.org, dan.carpenter@oracle.com, mhiramat@kernel.org Subject: [PATCH v3 10/22] x86,tracing: Add comments to do_nmi() References: <20200219144724.800607165@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