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=-13.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_PASS,USER_IN_DEF_DKIM_WL 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 5F70EC43381 for ; Tue, 19 Mar 2019 08:10:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2F49A204FD for ; Tue, 19 Mar 2019 08:10:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="QG3kAGNL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727453AbfCSIKi (ORCPT ); Tue, 19 Mar 2019 04:10:38 -0400 Received: from mail-io1-f66.google.com ([209.85.166.66]:39807 "EHLO mail-io1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725934AbfCSIKh (ORCPT ); Tue, 19 Mar 2019 04:10:37 -0400 Received: by mail-io1-f66.google.com with SMTP id e13so6739917ioq.6 for ; Tue, 19 Mar 2019 01:10:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=55JpN7h5Cm1wdHGXAMw2S4e/Hdymfa+JelMv9Ti/sbE=; b=QG3kAGNLbyq85ujdMaXiqMwjfehuwZ81+bJ8I9c/6v053fzGoNFXQ0ufhaMfDj0z1t vQYBqbPlPuYDziKjUNgLZq5aeCc8/zsFCKebyzSVf4sMamzJGWc5IsNNpLKAf5fBRFUA nCAJi5ULyolQX2LJ+2g9jbLk0yD+DfhRdHgvo0pDgBLrLJFHcyA5Y6z4p1KTjticyrWG MLSO4XJjsV4NpyHHIEQ7UFkghKgRNM7TbCoUI/g3ZSpsuQxFogoY2VL+KgG+zqXkOgAa 5bvQ88aSvIK3P0AEtu5UFurBuCST9/+EMdTvqHGPrfYhgEyIJ0Owzg9W8YpEAl/Y7e1P oL8w== 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=55JpN7h5Cm1wdHGXAMw2S4e/Hdymfa+JelMv9Ti/sbE=; b=TQ+Njz5RIvCURUo12Xbm3Z1ez5gsi3kjAUz4MtwqcdxCOlVMhzXHUuq4UlbuAkW1wF 5A5ab0BYyDMWJb6WRYTC2LAZqjMq22pw+WTWZyz4e/UOADXWW0cOVhaihU3OXc5GVb2F owWGpdGvRaZA+TqhaMItl1HQPbjp9c/HEJ3bXQWsep+vSdZIMYnPCDcKug/JkSgqbX12 VS+jIqEmiU1luuDW9zLZMd1t+ufQ4TD0Z2fXXCOLjsZUXL8mwpEi3DlzaNdxag/VSBT5 GSkNQ00/24pTfn0n1AnKl8W0aP3TcLAumnwe7a+syjEdBjesbc+F2qensI8mqsD3MqJp 7z3Q== X-Gm-Message-State: APjAAAUmNN1LYEd1V+yymVuvKGY/T3GoH7ejglz3i9Xmd6tU0PzeBtiX 7omFFK5WjyoMYHFKf3JM/IolXuE0JJ0HCZZaaKUiMQ== X-Google-Smtp-Source: APXvYqz0I8yoSsJxT+RbjlzMYlv9ljXdxfdfr5YpAA4VQrUGhsoR8/0d1i8nTKGaDIjcB9urAVgrBwDD2z8iqLeox24= X-Received: by 2002:a5d:834a:: with SMTP id q10mr562496ior.271.1552983036690; Tue, 19 Mar 2019 01:10:36 -0700 (PDT) MIME-Version: 1.0 References: <2a48dee7-b649-65a4-be5d-8b3374013cee@i-love.sakura.ne.jp> <201903180527.x2I5RQVp009981@www262.sakura.ne.jp> <20190318125019.GA2686@tigerII.localdomain> <20190318140937.GA29374@tigerII.localdomain> In-Reply-To: <20190318140937.GA29374@tigerII.localdomain> From: Dmitry Vyukov Date: Tue, 19 Mar 2019 09:10:25 +0100 Message-ID: Subject: Re: [syzbot? printk?] no WARN_ON() messages printed before "Kernel panic - not syncing: panic_on_warn set ..." To: Sergey Senozhatsky Cc: Tetsuo Handa , Petr Mladek , Sergey Senozhatsky , LKML , syzkaller Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 18, 2019 at 3:09 PM Sergey Senozhatsky wrote: > > On (03/18/19 14:42), Dmitry Vyukov wrote: > > > There is also SYSLOG_ACTION_CONSOLE_OFF, which disables logging. > > > > That one I somehow figured earlier, here is the exact check: > > https://github.com/google/syzkaller/blob/61f9c92f3a465025d2b9d91f429aaec968aeaa2a/sys/linux/init.go#L152-L155 > > OK, cool. > You probably would also want to add SYSLOG_ACTION_CLEAR to the list. It's not hard to add, but I would like to understand why exactly. syzkaller reads out console output from qemu, GCE VM, android phone all the time. So if something was already written and we read it out right away, it seems that clearing won't affect things. Does SYSLOG_ACTION_CLEAR affect only reading output via syslog syscall, /dev/something? In some setups we read out output with "dmesg -w" (should stream output as well) in absence of a better solution. Will this be affected by SYSLOG_ACTION_CLEAR?