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=-3.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 0A07AC433E1 for ; Mon, 17 Aug 2020 05:15:14 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BA8A42072E for ; Mon, 17 Aug 2020 05:15:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="aOIGVnn8"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="AdKggnTL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BA8A42072E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:To:Subject:Message-ID:Date:From:In-Reply-To: References:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=NnRG/bg9d2YCKghoM9+2q7a8DydPvV29RA3dW7W/N4w=; b=aOIGVnn82H2RA/t7AXRIDqbyk qA4MTWZtm0mzydq39QVHUfMiR/omtyWlDwr5BA9dFrntuZqrtozkz0J0+TqIFJ6THH4hmo03akYOx GaZrdg8v3wA7h4oIWeokUpk2bg2Nr+d0ng0PayaI9wGqeGPrrNhcn0SKVvktsQL/0jmf7mZM71t6H xdSzHukzRGQSYkRhe1du7mT+fouWeJ62ic6pQ9zxU9ncO4GPlleqBKVVn/ogIYWEPQ1e3Yfg80YEI mOxZpGvCnOVHhN2cA2oK3hedXgv5uR+fk4gF398FqrkwPNmsf8tBqzuFIGKYiZ0WiP+qEPy1RKK+2 iC9/8SCfQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1k7XSH-0003Cs-8p; Mon, 17 Aug 2020 05:13:09 +0000 Received: from mail-lf1-x141.google.com ([2a00:1450:4864:20::141]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1k7XSB-0003C5-RP for linux-arm-kernel@lists.infradead.org; Mon, 17 Aug 2020 05:13:05 +0000 Received: by mail-lf1-x141.google.com with SMTP id j22so7711046lfm.2 for ; Sun, 16 Aug 2020 22:12:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=8wbtEbHtU9M4Jod/JrcC7BZqQ8yoT12QXGXyBKx7JXA=; b=AdKggnTL3w6eZGHsRkx/100sgIDTgVVJxjW/eLCKNep4uW4Yl3iMpb4KJ/hcYsaTMx wP8SFf2QchKBG7PVGLeRaaVoNVzX1/pwr8T4EVeDUQhCo14ZxN8K2MYSOWOlZzFkEP5M Ciq0EA/yuDtUAFgNLJJGqxOJZhwMMqQoYlYyHZZb4R7DlqeXWidG15ku96JwrEUYkecI 8V6nyYxnw1wRy+xl1yfpgjlbh7n23OlsCIBXBzIFKFF4pVNcWMD2+SmoShkRxWfhxW2U fzykn0JV7r4VvJ1UM79GY/+iTN3SMoxwqLsYQmQmfutFRaxf0iASb0eXZ3RO9itt5p3T S8Eg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=8wbtEbHtU9M4Jod/JrcC7BZqQ8yoT12QXGXyBKx7JXA=; b=qwRkBVPKBNfM7CBCXhQGldqq/kZ/UgfhvGVPArlUL3Ajf5CU8dSdzvFMFL/iSGkdkJ ITQdWDznljR72vJbeUtsnsBmAMx7RiZ2sNhTChLZTQ9N+IyjeYasreREbgiuuObJ1vnS VUiYlcpeDqGdIEIiucq0aTU8wO9M3E8DuHjeKRYOuFvwwbqaWr8c6KQe8t1TC0mpHINj gqh4wFf8TEbvQWcGAqkScvKD1bgyakBuJjhZHvxASkErb8Br5Pt31B5UF3c1/XLldurF 55a+FYUJK3fov7ghEFk9aLux4FEiGKnGyI1Yf5dQkZosGrvTGahOELIXcfl9CVWEKVPM Kgtg== X-Gm-Message-State: AOAM533dtEdlVLa8JxOUKjy+KDPFHXwH5nmAAswuqgPH02L5uK38wx8X m9Uw5qo/DY4Ku0eI44ctNmzL88ErwCZ1/AlMEECYzA== X-Google-Smtp-Source: ABdhPJx5Xf4vEf6FrlCe2817ep57MgRm1K5c+hgJrods56LEUJS2xB8Xl7414M0vSYBeVkIvAAnFai/v6XBsFEsLoD4= X-Received: by 2002:a19:8705:: with SMTP id j5mr6468504lfd.122.1597641177454; Sun, 16 Aug 2020 22:12:57 -0700 (PDT) MIME-Version: 1.0 References: <20200811135801.GA416071@kroah.com> <20200811145816.GA424033@kroah.com> <20200813101703.566thqmnc2d7cb3n@holly.lan> <20200814141822.opahh33nfc5yodkb@holly.lan> In-Reply-To: <20200814141822.opahh33nfc5yodkb@holly.lan> From: Sumit Garg Date: Mon, 17 Aug 2020 10:42:43 +0530 Message-ID: Subject: Re: [RFC 0/5] Introduce NMI aware serial drivers To: Daniel Thompson X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200817_011304_039250_2B4847B5 X-CRM114-Status: GOOD ( 31.13 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Greg Kroah-Hartman , Jason Wessel , Russell King - ARM Linux admin , Doug Anderson , linux-arm-kernel , linux-serial@vger.kernel.org, Jiri Slaby , kgdb-bugreport@lists.sourceforge.net, Linux Kernel Mailing List Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 14 Aug 2020 at 19:48, Daniel Thompson wrote: > > On Fri, Aug 14, 2020 at 05:36:36PM +0530, Sumit Garg wrote: > > On Thu, 13 Aug 2020 at 15:47, Daniel Thompson > > wrote: > > > > > > On Thu, Aug 13, 2020 at 02:55:12PM +0530, Sumit Garg wrote: > > > > On Thu, 13 Aug 2020 at 05:38, Doug Anderson wrote: > > > > > On Wed, Aug 12, 2020 at 8:27 AM Doug Anderson wrote: > > > > > > One > > > > > > last worry is that I assume that most people testing (and even > > > > > > automated testing labs) will either always enable NMI or won't enable > > > > > > NMI. That means that everyone will be only testing one codepath or > > > > > > the other and (given the complexity) the non-tested codepath will > > > > > > break. > > > > > > > > > > > > > > The current patch-set only makes this NMI to work when debugger (kgdb) > > > > is enabled which I think is mostly suitable for development > > > > environments. So most people testing will involve existing IRQ mode > > > > only. > > > > > > > > However, it's very much possible to make NMI mode as default for a > > > > particular serial driver if the underlying irqchip supports it but it > > > > depends if we really see any production level usage of NMI debug > > > > feature. > > > > > > The effect of this patch is not to make kgdb work from NMI it is to make > > > (some) SysRqs work from NMI. I think that only allowing it to deploy for > > > kgdb users is a mistake. > > > > > > Having it deploy automatically for kgdb users might be OK but it seems > > > sensible to make this feature available for other users too. > > > > I think I wasn't clear enough in my prior reply. Actually I meant to > > say that this patch-set enables NMI support for a particular serial > > driver via ".poll_init()" interface and the only current user of that > > interface is kgdb. > > > > So if there are other users interested in this feature, they can use > > ".poll_init()" interface as well to enable it. > > Huh? > > We appear to speaking interchangably about users (people who sit in > front of the machine and want a stack trace) and sub-systems ;-). > > I don't think other SysRq commands have quite such a direct relationship > between the sub-system and the sysrq command. For example who are you > expecting to call .poll_init() if a user wants to use the SysRq to > provoke a stack trace? > Ah, I see. So you meant to provide a user-space interface to dynamically enable/disable NMI debug, correct? It will require IRQ <-> NMI switching at runtime which should be doable safely. -Sumit > > Daniel. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel