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=-2.2 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_SANE_1 autolearn=no 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 B715BC04EBF for ; Mon, 23 Sep 2019 10:05:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 846E220865 for ; Mon, 23 Sep 2019 10:05:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="AdFpKtal" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2436759AbfIWKFS (ORCPT ); Mon, 23 Sep 2019 06:05:18 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:40309 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406837AbfIWKFS (ORCPT ); Mon, 23 Sep 2019 06:05:18 -0400 Received: by mail-pg1-f193.google.com with SMTP id w10so7745197pgj.7 for ; Mon, 23 Sep 2019 03:05:18 -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=GN9uWlPH+mRUOKL6lisCqKrCCm1x4VV54XbjaAcOsJ0=; b=AdFpKtale+UdPAqRVVH0fkEU9i6SHcwJqBcZYBseNzuhLNt/NGzkC55oi6FdJOLoxV G8gYDbiJ/ypG3KYfe05iuGw4zN20zFWoKRZnpto7CEvt/noqO370oRIwYRXwKURk/CKv aPxVdXi2O/j6jwwc5X4Ew8Gfk5+NLYhkyuDnKWYDyhTfcWvaB9k12IzYX8tShQLmD4sx L83adHOpCCNixrrUI4IWEbL7G7ZZjS+VaFaWfTydnm5enr2oD7BD9y+G9uC1pbaVYsXz a0NfzT0rvg6uVMn0JLO69l0lTCNBkBwR4VeMNnneXHNUlLUeOLdmRB3a8URubE4GBMdR TByQ== 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=GN9uWlPH+mRUOKL6lisCqKrCCm1x4VV54XbjaAcOsJ0=; b=ZsylborIandRlIRWL42AgUvDaLZNXElDOvNlddTLOsB1KeNXeNZXUz1hHFnPgJhv/+ CvhGi+IF2twcJxJzKTXheqJby7ai/K9h3STqXKywUZWl131HGLsfAT8/CAdz8g5xIDnz rF8MbBbS7IrzB96h50KV7HUpVbyYCbM91zhlU6xqgxrZV6+uFhaChtYPfeCmaBb3MULD KOujZrILN8iBA2r11dm05pOIhyZW1FAtqJUYnfc+YiKtvrxwiDLNOT87Mn5Hq6DSVkgY Hku7t2pjVGh217PgOYZaXWPFavt1ituGNQvjZkslC2GTD6KR5LbtKd08kMBhn/bTSWsC Ckzw== X-Gm-Message-State: APjAAAUoxhbac7YXTUDzJLGLku+x7t8ssJXABwea89QcLh35ZerInbF+ sBAloCr6WukxCjXT+Zm61kBpV/Wx X-Google-Smtp-Source: APXvYqymz9dteM+jXvuRx1ZHLlJbP4zvdHYa0ZZN0LO8z3y9tkVXTV3Vwftor/JPVb1+/OrL/pdRNQ== X-Received: by 2002:a63:c851:: with SMTP id l17mr4954033pgi.6.1569233117617; Mon, 23 Sep 2019 03:05:17 -0700 (PDT) Received: from localhost ([110.70.15.104]) by smtp.gmail.com with ESMTPSA id a13sm12231312pfg.10.2019.09.23.03.05.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Sep 2019 03:05:16 -0700 (PDT) Date: Mon, 23 Sep 2019 19:05:13 +0900 From: Sergey Senozhatsky To: zhe.he@windriver.com Cc: pmladek@suse.com, sergey.senozhatsky@gmail.com, rostedt@goodmis.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] printk: Fix unnecessary returning broken pipe error from devkmsg_read Message-ID: <20190923100513.GA51932@jagdpanzerIV> References: <1568813503-420025-1-git-send-email-zhe.he@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1568813503-420025-1-git-send-email-zhe.he@windriver.com> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (09/18/19 21:31), zhe.he@windriver.com wrote: > > When users read the buffer from start, there is no need to return -EPIPE > since the possible overflows will not affect the output. > [..] > - if (user->seq < log_first_seq) { > + if (user->seq == 0) { > + user->seq = log_first_seq; > + } else if (user->seq < log_first_seq) { > /* our last seen message is gone, return error and reset */ > user->idx = log_first_idx; > user->seq = log_first_seq; A tough call. User-space wants to read messages which are gone: log_first_seq > user->seq. I think returning EPIPE is sort of appropriate; user-space, possibly, can printf(stderr, "Some /dev/kmsg messages are gone\n"); or something like that. -ss