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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 B8E2EC43387 for ; Tue, 18 Dec 2018 17:37:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8633E21873 for ; Tue, 18 Dec 2018 17:37:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727252AbeLRRhv (ORCPT ); Tue, 18 Dec 2018 12:37:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:40648 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726548AbeLRRhv (ORCPT ); Tue, 18 Dec 2018 12:37:51 -0500 Received: from gandalf.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E3BDA20578; Tue, 18 Dec 2018 17:37:49 +0000 (UTC) Date: Tue, 18 Dec 2018 12:37:48 -0500 From: Steven Rostedt To: Peter Zijlstra Cc: Sergey Senozhatsky , Borislav Petkov , Sergey Senozhatsky , Petr Mladek , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [RFC][PATCH] printk: increase devkmsg write() ratelimit Message-ID: <20181218123748.3aadd16c@gandalf.local.home> In-Reply-To: <20181218172109.GK15430@hirez.programming.kicks-ass.net> References: <20181218104812.GC15430@hirez.programming.kicks-ass.net> <20181218111701.GA32522@jagdpanzerIV> <20181218114709.GF7485@zn.tnic> <20181218130750.GA665@tigerII.localdomain> <20181218142623.GH7485@zn.tnic> <20181218145558.GD665@tigerII.localdomain> <20181218150313.GI7485@zn.tnic> <20181218151455.GE665@tigerII.localdomain> <20181218152413.GJ7485@zn.tnic> <20181218165217.GA534@tigerII.localdomain> <20181218172109.GK15430@hirez.programming.kicks-ass.net> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 18 Dec 2018 18:21:09 +0100 Peter Zijlstra wrote: > On Wed, Dec 19, 2018 at 01:52:17AM +0900, Sergey Senozhatsky wrote: > > On (12/18/18 16:24), Borislav Petkov wrote: > > > On Wed, Dec 19, 2018 at 12:14:55AM +0900, Sergey Senozhatsky wrote: > > > > Right, but unlike log_buf_len, devkmsg is a bit close to a "binary" knob: > > > > either all messages or none; > > > > > > ... which is perfectly fine for a debugging session. > > > > But devkmsg ratelimits systemd errors, so one does not even know that > > "some debugging is required". For instance from my x86 box: > > > > Unmounting /home... > > [..] > > home.mount: Mount process exited, code=exited status=32 > > Failed unmounting /home. > > > > I don't want to debug systemd, I want to know that something didn't > > work out. 10 messages max and 5 seconds interval looks a bit too strict. > > Again, complain to system-doofus for printing so much crap to somewhere > it should not print to begin with. I've been saying that it would be good to make the kmsg be a separate buffer that just gets interleaved with the kernel buffer. Userspace processes should never be able to overwrite messages from the kernel. -- Steve