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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 CBB76C34047 for ; Wed, 19 Feb 2020 17:07:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A11A920801 for ; Wed, 19 Feb 2020 17:07:56 +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="tJgwSjzo" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726707AbgBSRHz (ORCPT ); Wed, 19 Feb 2020 12:07:55 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:37136 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726598AbgBSRHy (ORCPT ); Wed, 19 Feb 2020 12:07:54 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=2xN/67dkbMYjl8utBRoK3KoAvhWmqTFf76Sk2gS40xQ=; b=tJgwSjzoN+WUNV7puG9hFY/ykA YHoCQ/AJ1Ca1eVqD2pg5eMy3goeHDGH7kIJ8diYJCgY4mJf06A7yS/aSUsjAChvDpA3wCwge7eRJt jqc65Ha8YU8y4ErKlwNq/Znw5TPZm42MdmYizp1rGMbxohlw1bA/wLUjpNeC8RK91FcdWdD+2xUqj iuE2iDI97h6c8pDTHBoXtUc7YcOsWmVL9DAKl9nN6wbGyURddIETe+pXtJnaSv0DjHEmWR+xrMNG5 DWReefJ8A4jedOZpsT22R+svm5kK0CZRjgFhaRRWitqczRrtqFTWAyrSci309BZ6k2Y/rvlpAekc1 XZ/rSVsQ==; 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 1j4Sop-0001Ax-FG; Wed, 19 Feb 2020 17:07:27 +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 526D9300565; Wed, 19 Feb 2020 18:05:33 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id BF588202287DD; Wed, 19 Feb 2020 18:07:25 +0100 (CET) Date: Wed, 19 Feb 2020 18:07:25 +0100 From: Peter Zijlstra To: Borislav Petkov Cc: Steven Rostedt , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.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, Will Deacon , Marc Zyngier , Michael Ellerman , Petr Mladek Subject: Re: [PATCH v3 01/22] hardirq/nmi: Allow nested nmi_enter() Message-ID: <20200219170725.GO18400@hirez.programming.kicks-ass.net> References: <20200219144724.800607165@infradead.org> <20200219150744.428764577@infradead.org> <20200219103126.33f67cf3@gandalf.local.home> <20200219165650.GB32346@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200219165650.GB32346@zn.tnic> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 19, 2020 at 05:56:50PM +0100, Borislav Petkov wrote: > On Wed, Feb 19, 2020 at 10:31:26AM -0500, Steven Rostedt wrote: > > Probably should document somewhere (in a comment above nmi_enter()?) > > that we allow nmi_enter() to nest up to 15 times. > > Yah, and can we make the BUG_ON() WARN_ON or so instead, so that there's > at least a chance to be able to catch it for debugging. Or is the box > going to be irreparably wedged after the 4 bits overflow? It's going to be fairly buggered, because at that point in_nmi() is going to be false again. It might survive for a little, it might not.