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_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 C6D55C2BA83 for ; Thu, 13 Feb 2020 09:08:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 99D6120848 for ; Thu, 13 Feb 2020 09:08:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="VjrhEKjg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729619AbgBMJIB (ORCPT ); Thu, 13 Feb 2020 04:08:01 -0500 Received: from mail-pf1-f194.google.com ([209.85.210.194]:35568 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726232AbgBMJIA (ORCPT ); Thu, 13 Feb 2020 04:08:00 -0500 Received: by mail-pf1-f194.google.com with SMTP id y73so2765774pfg.2 for ; Thu, 13 Feb 2020 01:08:00 -0800 (PST) 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=iZ4ALMIQ3+TkLwExvTpCpZXbkNrLF9yBShKjZ2USbmI=; b=VjrhEKjg/eQQL39kqbYW4sTUO7Dkc4Lwr+Txc2E6nE9o78H+RPowJ5/THyptvadMzN hLmpo02dDGTpF6sjQQJCR2DbqfEUaBtJFqewYeZ3bOzekqvoa8svO7s4rAaeyosodBNM oA9Mdq6PTJdrAlcBdB1RVTAyyN84Z/zRhOv8UAQcIIYYQxhdAAz7/fyYYd+KCF6/erkP aGxry2onFhnMIN50g04l8s9InEvOyUGkLkBjg5nlXl/9eSq4LnmogJC9hkwR33KFDyB3 8tuhDKc4Ar5YYgl/hvbYN+sgB1JNdWqsitexCsumRFuDSPkNs2LHsSTNqGhrtEvalu4v SlSg== 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=iZ4ALMIQ3+TkLwExvTpCpZXbkNrLF9yBShKjZ2USbmI=; b=jcbvGZyWRT6aV9o3xofKDjJJ/3OIiD4GcjVYyqGdW8Jco7MnHBze9pqU9xuiisVL3z 7SAzaOShpUtrb7zfa6e5UzPM1OJgINzyCTybBe5aSIdzijP/pQt1xuHFzVXk0Aypidfs 6LazzYiyqasgK5VSk/W/QQsUcxHb8/cBBbUax9SXF+KANBGj+RlCYtoTAmqmTm1mdZlK mQp1Rs+2y4RVnIGthqDyaoz6hfF6ENXxPUe8V0f13pFRMVsUKtCHXV6wJFce5bpmFx3p LnPrBb96gCNfthwb5m3AhJaXDvac1EPlv+xR1PQ9P+9hQ0TgOLDplrKtF4aaw3LSzn1r RplQ== X-Gm-Message-State: APjAAAUMXcbT84fdegAYHnr0IVNSXAvkjFpf5JqBD+i+AZVccc/Wsbz3 I1h5zR+k70JVVMS4AISgXOc= X-Google-Smtp-Source: APXvYqzHEVTHskgrdP+FV0zdgL5k5qeBTwi8pTz/gKF/KF6N5daLmf/6qact8sPmkxlTbcKlT6X8vg== X-Received: by 2002:a62:1a97:: with SMTP id a145mr16870284pfa.244.1581584880034; Thu, 13 Feb 2020 01:08:00 -0800 (PST) Received: from localhost ([2401:fa00:8f:203:5bbb:c872:f2b1:f53b]) by smtp.gmail.com with ESMTPSA id k1sm2259597pfg.66.2020.02.13.01.07.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Feb 2020 01:07:58 -0800 (PST) Date: Thu, 13 Feb 2020 18:07:57 +0900 From: Sergey Senozhatsky To: John Ogness Cc: Petr Mladek , Peter Zijlstra , Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Andrea Parri , Thomas Gleixner , kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] printk: use the lockless ringbuffer Message-ID: <20200213090757.GA36551@google.com> References: <20200128161948.8524-1-john.ogness@linutronix.de> <20200128161948.8524-3-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200128161948.8524-3-john.ogness@linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (20/01/28 17:25), John Ogness wrote: [..] > - while (user->seq == log_next_seq) { > + if (!prb_read_valid(prb, user->seq, r)) { > if (file->f_flags & O_NONBLOCK) { > ret = -EAGAIN; > logbuf_unlock_irq(); > @@ -890,30 +758,26 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, > > logbuf_unlock_irq(); > ret = wait_event_interruptible(log_wait, > - user->seq != log_next_seq); > + prb_read_valid(prb, user->seq, r)); > if (ret) > goto out; > logbuf_lock_irq(); > } > > - 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; > + if (user->seq < r->info->seq) { > + /* the expected message is gone, return error and reset */ > + user->seq = r->info->seq; > ret = -EPIPE; > logbuf_unlock_irq(); > goto out; > } Sorry, why doesn't this do something like if (user->seq < prb_first_seq(prb)) { /* the expected message is gone, return error and reset */ user->seq = prb_first_seq(prb); ret = -EPIPE; ... } ? -ss