Received: by 2002:ad5:474a:0:0:0:0:0 with SMTP id i10csp2482187imu; Thu, 10 Jan 2019 15:07:20 -0800 (PST) X-Google-Smtp-Source: ALg8bN7RC4piMH7n+XTLTB9KSmVsW/tgaoxKBgnUR+MAr8ihCNx0LP0w6HBe5c/T8XtSERp80cMo X-Received: by 2002:a17:902:43e4:: with SMTP id j91mr1702653pld.147.1547161640562; Thu, 10 Jan 2019 15:07:20 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1547161640; cv=none; d=google.com; s=arc-20160816; b=jGWGPk/8+zOf+pENyFFoyzGO+owu5SHBQGtM0XKqgYW/4UGDqaRs8YSzbI9h/hDKku WNrvsVluJxIOy97BwgAgByfVn+RBNhyHsKRqW40cxU5FySqUZtfXVD/gN0U8FsISyh+U OwSaoMjY0ssvDW/zcDPHQXl6Y3imks/fH9BpC2oFZzzq2NmZIKr2uh+1mHuy34CheSMU Wm+SzgpV6kFbUxXLtKzemKV0vc/9tfoEIHXzjqKDt2eeA5fErt7t5sVjqBL/h7VuhLAo wX6ud4P4+PqG6BhBvsSfLjNnb2iiYvzVV00ezolqB07/eMWM1oamn1iW2kmqzMLM3mNK FxGw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:user-agent:in-reply-to :content-disposition:mime-version:references:message-id:subject:cc :to:from:date:dkim-signature; bh=prrTEl/O1mn8pEBS0AEe6chxDE6RBTZn76+uyV1l/z4=; b=KDCuO0BRy1QeuzxRKlJl6K7xIfI5w2aQZI02tnLO/jThPbiKdV1tsLcfCGVG/szz17 L0ry5le4nNVSl05Fk7qrTNn38cME2BrvVAJP6iastATBelKL/sEp+KI31svHLTaKgeYs Mf5XZwbQa/wMQNTxjZSgM2D2cUMLjzs/38TPN1Pk7UIVScJuzU/auzv62o27kDlZbPXW PLIAcpXkuyCUx+2t9j71V1JNMooYG82oq7rYLlGqmQhRXRagUwnPQFHm0EB2nbfpjjno /Z4iiOzCAK7KXSmJcHHZR+EWkad1Vlc394CQCya7/0dOW2V8GeNo8suqkHxsGlMfr2fB ug9w== ARC-Authentication-Results: i=1; mx.google.com; dkim=fail header.i=@infradead.org header.s=bombadil.20170209 header.b=B9SkaYoZ; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id u3si24413734pgj.300.2019.01.10.15.07.02; Thu, 10 Jan 2019 15:07:20 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=fail header.i=@infradead.org header.s=bombadil.20170209 header.b=B9SkaYoZ; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728999AbfAJUDI (ORCPT + 99 others); Thu, 10 Jan 2019 15:03:08 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:35338 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726242AbfAJUDI (ORCPT ); Thu, 10 Jan 2019 15:03:08 -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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=prrTEl/O1mn8pEBS0AEe6chxDE6RBTZn76+uyV1l/z4=; b=B9SkaYoZd/wV9XMafsHVbPK2S vm46mM1w1YM4Hu4GqgioDlx/HYJcsSfrW8fqc3AeB0hIYxSehADi8otcoAzEZbBDbUyN/UTsGiW5c +R6RERORijCtJsvnHZmoS4eNcwMreVgrumGIDyg0nq6Y/mwK0unQcQwru84M0JFo5hsE/9uYhwMNs 0JrHn/I8m9vfxt/YJ/JserMisvgBAF+1kf+cclefeGxi22ciWPQWvUd8eLcVHENze1d33w9NfkxCO NkQg/+BQz4vjY7MgeZxKFhaLPBpwIFFdaR2V+tGQUURCRSxMp6b2e3ZNV2wk6VKUxNUbTxnDj1nh8 y9I2f/PpQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1ghgXi-0007ys-UY; Thu, 10 Jan 2019 20:03:07 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 9D5E89844AF; Thu, 10 Jan 2019 21:03:03 +0100 (CET) Date: Thu, 10 Jan 2019 21:03:03 +0100 From: Peter Zijlstra To: Zhenzhong Duan Cc: LKML , longman@redhat.com, SRINIVAS Subject: Re: Question about qspinlock nest Message-ID: <20190110200303.GG2861@worktop.programming.kicks-ass.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Thu, Jan 10, 2019 at 04:02:53PM +0800, Zhenzhong Duan wrote: > Hi Maintainer, > > > There is a question confused me for days. Appreciate an answer. > > In below code, the comment says we never have more than 4 nested contexts. > > What happen if debug and mce exceptions nest with the four, or we ensure it > never happen? MCE and NMI really should not use spinlocks at all since they cannot be masked.