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=-2.4 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 5919DC43219 for ; Fri, 26 Apr 2019 16:18:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 244E52084F for ; Fri, 26 Apr 2019 16:18:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="DLMWO8Q0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726303AbfDZQSv (ORCPT ); Fri, 26 Apr 2019 12:18:51 -0400 Received: from mail-pf1-f194.google.com ([209.85.210.194]:41822 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726049AbfDZQSv (ORCPT ); Fri, 26 Apr 2019 12:18:51 -0400 Received: by mail-pf1-f194.google.com with SMTP id 188so1957584pfd.8 for ; Fri, 26 Apr 2019 09:18:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=de4bNe6ru3D+sukfth4RLcI7Zhp1IspHKcI6VPzFIT0=; b=DLMWO8Q00VLneKlpiu6QGqSzIXoFQXOSrbGxnAP2X7EVfPq91WjP7D7CfqmbeU8gm7 6iM4WIdBgyw/SiCdQDL/tifZ1jCvGkIZwHAzWYuX4JV46OVQ8plIPPB3qJB5lkwP7uVL R4qAex8maEqzJEohumuEfuWnkrOTP+gqW/BRoK4B2sAg+K9u/DT6+100coIsJGFe6aK3 ZrsrNzuu15FJY4yorZ43fHbvxn4eSvnaNjE0Gx0vq5IcvY9Lhx8kQBM0zjq9mwwwlISw PdAWSgiC/8Vb9G8ydR66VnE2w1TTP0Ojtz05faNhZw5YdnxUwLHwX/FdCdbqE29cYJ9w 4JGw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=de4bNe6ru3D+sukfth4RLcI7Zhp1IspHKcI6VPzFIT0=; b=ULAQ2aQkWitERpsUMu5P4cxJTzp2mD/r7e+RKesAQYU0R2dSQ3aQq0QahOzdf0Wll3 qKYrrZ2Q6+3FIMLU4etnKYWVsrcKpF+8RFl/Ex/ppehpJq2rAH2aQtZkfvCCPJXbq16s 5tlTNV0CYbcoGhN3+bRdiQizcncY9LDYq10FzSnYJJyRvaJ4t79tancCl7J8cS5BTsYX y6QMuy39vdp2Vfa81ea+kZJH4E6v0+2pjLLxz/dOB8aJKzbBrYqFREhrk82Thuu0ijZO 3HkaKM1SBKq28LZYwbjODWvwk5dCkjEZGxg8B0hnEwWKZeCb3iEg1RXbpVs1ofiYBfDO BiDQ== X-Gm-Message-State: APjAAAUbN+CePRZV7PLGRKk6qowX9vQgLJ+72vDtcEm5PAIKDKVFPNBU SPodE+ZmscmwxgxgPtb4wPlcM9Pr X-Google-Smtp-Source: APXvYqx15GFlsFQGXDfEwBwENj7CEB0nt9L7aalCE9ijLJoaPHbYdwI2tQgT0tOiubwaG8OX+l07LQ== X-Received: by 2002:a62:ee0a:: with SMTP id e10mr47038892pfi.6.1556295530046; Fri, 26 Apr 2019 09:18:50 -0700 (PDT) Received: from localhost ([121.137.63.184]) by smtp.gmail.com with ESMTPSA id l4sm35149983pgh.17.2019.04.26.09.18.48 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 26 Apr 2019 09:18:49 -0700 (PDT) From: Sergey Senozhatsky X-Google-Original-From: Sergey Senozhatsky Date: Sat, 27 Apr 2019 02:16:40 +0900 To: Petr Mladek Cc: Feng Tang , Andrew Morton , Steven Rostedt , Sergey Senozhatsky , linux-kernel@vger.kernel.org, Aaro Koskinen , Kees Cook , Borislav Petkov , Sergey Senozhatsky Subject: Re: [PATCH v4] panic: add an option to replay all the printk message in buffer Message-ID: <20190426171640.GA7413@tigerII.localdomain> References: <1556199137-14163-1-git-send-email-feng.tang@intel.com> <20190426074934.seje2tn5p6fsuwaq@pathway.suse.cz> <20190426135316.GA505@tigerII.localdomain> <20190426141426.h7hpvhr3rqp7umbk@pathway.suse.cz> <20190426164302.GA26127@tigerII.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190426164302.GA26127@tigerII.localdomain> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (04/27/19 01:43), Sergey Senozhatsky wrote: [..] > > The console waiter logic is effective but it does not always > > work. The current console owner must be calling the console > > drivers. > > > > > Hmm, we might have a bit of a problem here, maybe. > > > > Hmm, the printk() might wait forever when NMI stopped > > the current console owner in the console driver code > > or with the logbuf_lock taken. > > I guess this is why we re-init logbuf lock from panic, > however, we don't do anything with the console_owner. > > > The console waiter logic might get solved by clearing > > the console_owner in console_flush_on_panic(). It can't > > be much worse, we already ignore console_lock() there, ... Hmm, or maybe we are fine... console_waiter logic should work before we send out stop IPI/NMI from panic CPU. When we call flush_on_panic() console_unlock() clears console_owner, so panic_print_sys_info() should not deadlock on console_owner. It's probably only problematic if we kill a console_owner CPU and then try to printk() (from smp_send_stop()) before we do flush_on_panic()->console_unlock(). -ss