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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,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 442E9C4646B for ; Wed, 26 Jun 2019 07:59:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1B8802133F for ; Wed, 26 Jun 2019 07:59:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ifNVdZNF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727093AbfFZH7P (ORCPT ); Wed, 26 Jun 2019 03:59:15 -0400 Received: from mail-pl1-f193.google.com ([209.85.214.193]:44396 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726042AbfFZH7P (ORCPT ); Wed, 26 Jun 2019 03:59:15 -0400 Received: by mail-pl1-f193.google.com with SMTP id t7so976423plr.11 for ; Wed, 26 Jun 2019 00:59:14 -0700 (PDT) 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=m4ccwwpO5oRzKymdnY/55sXpZJv1GlqtCN/M5c5AvmY=; b=ifNVdZNFnY/2v4zh/dDKfkaBnMcIoW/YPwoxRXpDgBPjIpbAtY9RULlxulJ0n8osIW oikinqGd5ACHyhyJfm8gEuflttq5znCoqv/p9W9o3DxtDKiY/dP6y0QK32QnOFT1ly8W OcslnNnxHhZ5fimkjloj72FgwhbwVoVMRBnmB3Dfowpb+y5KghzISjOl/m7LRcPNmTHa Sp4glE1irTzNlJ7dDmLNmoSbPP8ehBwblXYBdax57+UceVwebOuP7G6weJfhcJLCPFdb BCGvhc1R6AjuxfCzusrGdYXVQMx46iZqUGeUdt7S88Ci2Dbu5+rvzOl4dNhoau1g+3PO GULQ== 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=m4ccwwpO5oRzKymdnY/55sXpZJv1GlqtCN/M5c5AvmY=; b=Fdf/XMeH4pQjMZXMboZh4zXwEX6yRmSUpQH+1NwBhgbLn+5k1evdKZrVfUwOtSTNNK MXb4LinGW+Fi5KH+Ds5S+bYETvC+Pjsz06FTv2BLckX4NKOS73+zZ8jMGx/ECyx27202 WTZqgWlsFlK278pTviyKWIBcW3VOxpRXsXFRMLd/9cDmt1v1AlTTdCQtAWj4fs57hgdF ki7wXZ6P2FIbJt2uAK91SVyA6NwRYhPoVjHS59JyOEyvypSdEHOwluPzzU7CmAzpMjcP b1rTud8XalCvaaw+32OrtVXFIi0I5k14Rl7ckaxwvWp093iLSkmRQ2jBEcgXsLh6hYXr JwUQ== X-Gm-Message-State: APjAAAVWDPsQpGKzHk5g1gCK7A7rACajQWypmuXvHB+7OgD3/alMKeEO gL5UiR2DmXw1tRdMV7Fc1lI= X-Google-Smtp-Source: APXvYqwb0Kc9S0n5E7F36S1KdjVeYBGXxGk/mESd3n76+oCdkdana+gh3ApUne4sMUzL5pIyTnPR5Q== X-Received: by 2002:a17:902:5ac4:: with SMTP id g4mr3986808plm.80.1561535954603; Wed, 26 Jun 2019 00:59:14 -0700 (PDT) Received: from localhost ([175.223.45.10]) by smtp.gmail.com with ESMTPSA id k22sm19500304pfg.77.2019.06.26.00.59.13 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 26 Jun 2019 00:59:13 -0700 (PDT) Date: Wed, 26 Jun 2019 16:59:10 +0900 From: Sergey Senozhatsky To: Petr Mladek Cc: John Ogness , Sergey Senozhatsky , linux-kernel@vger.kernel.org, Peter Zijlstra , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Andrea Parri , Thomas Gleixner , Sergey Senozhatsky Subject: Re: [RFC PATCH v2 1/2] printk-rb: add a new printk ringbuffer implementation Message-ID: <20190626075910.GA2936@jagdpanzerIV> References: <87imt2bl0k.fsf@linutronix.de> <20190625064543.GA19050@jagdpanzerIV> <20190625071500.GB19050@jagdpanzerIV> <875zoujbq4.fsf@linutronix.de> <20190625090620.wufhvdxxiryumdra@pathway.suse.cz> <20190625100322.GD532@jagdpanzerIV> <87woh9hnxg.fsf@linutronix.de> <20190626020837.GA25178@jagdpanzerIV> <87mui43jgk.fsf@linutronix.de> <20190626074718.n7fmxugeul3lyyq6@pathway.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190626074718.n7fmxugeul3lyyq6@pathway.suse.cz> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (06/26/19 09:47), Petr Mladek wrote: [..] > If the data might change under the hood then we have bigger > problems. For example, there might be a race when the trailing > "\0" has not been written yet. Current printk would not handle such cases. I'm only talking about transition from one consistent state to another, when sprintf(NULL, ptr) == A && sprintf(buf, ptr) != A Wether it's a corner case or not is entirely unclear to me but I probably would not call it "an impossible scenario". -ss