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=-2.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 3F558C07E85 for ; Tue, 11 Dec 2018 08:07:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 02BD320811 for ; Tue, 11 Dec 2018 08:07:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="fiTzXMAl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 02BD320811 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726211AbeLKIHt (ORCPT ); Tue, 11 Dec 2018 03:07:49 -0500 Received: from mail-pg1-f195.google.com ([209.85.215.195]:41254 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726050AbeLKIHt (ORCPT ); Tue, 11 Dec 2018 03:07:49 -0500 Received: by mail-pg1-f195.google.com with SMTP id 70so6280095pgh.8; Tue, 11 Dec 2018 00:07:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=dtsah3hj3YglgtT4y8wajXfYCGKdjBGIw6dGZnIEYkU=; b=fiTzXMAlIVT6mau0PrKHi41nMq4d0t8CIUfdBoe0aiI3xSwNy8FN9n04aTmnVTEaHu Z0+MqBhbFc3TdkvRLXPXAX2Xl9gHQHE0Xn1ZQs+ZeTVxxA48hFAnYa9N70lPLTekFTGg wg4MrVKuwJUTJ4lUMq9avWa5MO17iD+PjyC+JWbhU8EYV2qhARD2pycr7Pqg+KF5SIjM DCbykyzKtivJNJ2h9UbOUE+RcamX4S2nwfO8c4DBA8FcvQccbavZF2Ix/bbDBbU48q7u NjSFOq/iqpJcRv0XsMRIXxxzGdCw6cJodcTI6pqASFDjf498CVLthKjUx1heIieIcZ8N lf9Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=dtsah3hj3YglgtT4y8wajXfYCGKdjBGIw6dGZnIEYkU=; b=c9yUA2XMXt/EM7i4+BwKx+8z/zmrVUYNPRynXynbILAd4LSi7IWMWK5Sfe+2z1MDta dDB/Hc9QZoBVYZ5xXxkbK8XEqXHwrlkNlWHNCvfq62bfrfHoSO8lMvHR/GwDWoL0R2Dw dOtN3ZgqmNDjzeUdwbNsYYTqQyiR0vakwis87p7NGI8rTnUWVwS3GHPlH4k+E1jpIO8l lZmwcNhf+qWW0n7xszN5ikc5c3Lk27v30W9hokL+z3ibLwfzf6rOklbEQc90OroR1a6v sEJfJSB6yG9Atnurw5oyKRDLFD3jlujLmbORDAMXxBWg+HTlA2oabIso9MV0REjOpDat WLZw== X-Gm-Message-State: AA+aEWZolXoShSoU7TlDfHx9yChkoIv7ojLj8Tk1+NC9d5oC/HiK9FZt FdcpTL8qsCcFeOGMif+udx/t8F0D X-Google-Smtp-Source: AFSGD/U4lQ2c8GF0emWKUResBZIQzORfuKBg+e61AT9gX7H7jJ31cKFLiTfLljgbEJzt0I9dgLVxqQ== X-Received: by 2002:a63:fd0a:: with SMTP id d10mr13949394pgh.164.1544515668497; Tue, 11 Dec 2018 00:07:48 -0800 (PST) Received: from localhost ([175.223.2.144]) by smtp.gmail.com with ESMTPSA id m67sm22251090pfm.73.2018.12.11.00.07.46 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 11 Dec 2018 00:07:47 -0800 (PST) Date: Tue, 11 Dec 2018 17:07:43 +0900 From: Sergey Senozhatsky To: Petr Mladek Cc: Feng Tang , Sergey Senozhatsky , Peter Zijlstra , akpm@linux-foundation.org, bp@suse.de, keescook@chromium.org, mm-commits@vger.kernel.org, sergey.senozhatsky@gmail.com, stable@vger.kernel.org, tglx@linutronix.de, Steven Rostedt , Sasha Levin , Andi Kleen , linux-kernel@vger.kernel.org Subject: Re: + panic-avoid-the-extra-noise-dmesg.patch added to -mm tree Message-ID: <20181211080743.GB521@jagdpanzerIV> References: <20181205022654.GA503@jagdpanzerIV> <20181205024713.nqyt6qiamokq7qtl@shbuild888> <20181205025728.GC503@jagdpanzerIV> <20181205052912.GA423@jagdpanzerIV> <20181205080044.GA11190@jagdpanzerIV> <20181205154620.4dqtledc2duhrp2c@shbuild888> <20181206035825.jz2bfh3errj23rjq@shbuild888> <20181207095004.GB3729@jagdpanzerIV> <20181210094554.z5n7dmkrnlcpygg4@shbuild888> <20181210155705.qowbi7xvszzfonzk@pathway.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181210155705.qowbi7xvszzfonzk@pathway.suse.cz> User-Agent: Mutt/1.11.1 (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (12/10/18 16:57), Petr Mladek wrote: > > > (masked out) and on panic_cpu disables only SDEI (interrupts from firmware, > > > if I got it right); so it seems that arm64 can handle IRQs after panic. And > > > if there are platforms that handle IRQ (including sysrq) after panic, then > > > both options - making printk a noop or keeping local irqs off - maybe can > > > cause some problems. Or maybe not. We better ask arch people. > > > > Yes, this is very valid concern. And after Petr and you raised it, I did > > some experiments with 3 x86 platforms at my hand, one Apollolake IOT device > > with serial console, one IvyBridge laptop and one Kabylake NUC, the magic key > > all works well before panic, and fails after panic. But I did remember the > > PageUp/PageDown key worked on some laptop years ago. And you actually raised a > > good question: what do we expect for the post-panic kernel? > > I am not sure why it does not work. But it would be nice if sysrq > worked. Absolutely. [..] > I still think that calming down printk() is acceptable when > it can be restored from sysrq. I would agree; peeking one of the two solutions, printk patch is probably preferable. > I think that only few people might be interested into debugging > post-panic problems. We could print a warning for them about > that printk() has got disabled. Dunno. This _maybe_ (speculation!) can upset folks on those platforms that have sysrq working after panic. printk is a common code. I'm probably missing a lot of things here, but just in case, I'm not sure at which point the idea of patching some files under arch/x86 directory was ruled out and why. -ss