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=-3.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 8637AC433E1 for ; Wed, 26 Aug 2020 10:01:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 616E120786 for ; Wed, 26 Aug 2020 10:01:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="rZYrbaDK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728487AbgHZKBT (ORCPT ); Wed, 26 Aug 2020 06:01:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728041AbgHZKBS (ORCPT ); Wed, 26 Aug 2020 06:01:18 -0400 Received: from mail-pf1-x442.google.com (mail-pf1-x442.google.com [IPv6:2607:f8b0:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AB50EC061574 for ; Wed, 26 Aug 2020 03:01:17 -0700 (PDT) Received: by mail-pf1-x442.google.com with SMTP id m71so724151pfd.1 for ; Wed, 26 Aug 2020 03:01:17 -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; bh=lN7CDYsBp+g8H+Q27SUJ+E2mec/tKF8dfPsVSHDg050=; b=rZYrbaDKZEGSb9NrM2Wt0vKPzu5pSLr7Z4soaF4BK4oG6IipXyLFdENSTzR4AXtYBp L9wZEWqNiqlq+e1Ehqss9bk8toyUAh/MRXvdjVU41UmfjkIgOL/Nl5nYwY56g+5OtCXD 1VduYt2QKNS+wORnDVcOEmFtpCMlsdM5TU7WADFxW/w0ZxNJLSgJgd1vtaN5ziSTYERh qrh2gko/0nAWQ1FnuPVeqNhihUO4Vi7+glLJ6C3Pp9lQ8K1jlDB8aW7JSpDS2FgDeOOF 9oamUieaJr3PetzWIJeYJCYnvbEM1IMuunwNh9GXFGkXDPE04lA225VhJBGuHhoI1z6V cqAQ== 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; bh=lN7CDYsBp+g8H+Q27SUJ+E2mec/tKF8dfPsVSHDg050=; b=kdEJjiH70OKAq+g+jErybiHRBolGRRYkSEXlDktSrImVL+xXq3fjcBSB68FqZHnuF2 C4IngypyKdn2LEn0OBepUHQSpcAbOabQNlhu4nBbu6OQ/SDBGffQIqR7cZGYHFjWqBxc VnVP9kiUL8yy9d0sWRuvNxhUhGZkY8zwI4qg1kA2DpO7AZ7GoObfzZ1O7t7bHsC4a8xI 5NYMzkdZRL2o5SysBrQe/A3a+HtHPdM0tFyGptaZAsSu6DA8tAKLfwY/OO9WqsmU93So Wsz9x5c5RjsrUh8gmLMRWeOFXyKR8j7KZPcsytLTFrNWLMhBhVsrfG4+2qXleBJ9/MVd 3Dcg== X-Gm-Message-State: AOAM5310GcDK96awuLxXuIi5DdWBaBgMInMhmc0mL8bXx4LOn5OwdA2v 99G0/4V2lSXvphP8KB2iDqY= X-Google-Smtp-Source: ABdhPJxYhjBzb/1wST94Ldy6U50tkVIofIqQYck5r6/B+ywfwdF7ykYwG15AippqtuGIGa8U2xmnKg== X-Received: by 2002:aa7:8490:: with SMTP id u16mr5709733pfn.258.1598436077192; Wed, 26 Aug 2020 03:01:17 -0700 (PDT) Received: from localhost ([2409:10:2e40:5100:6e29:95ff:fe2d:8f34]) by smtp.gmail.com with ESMTPSA id o2sm1762049pjh.4.2020.08.26.03.01.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Aug 2020 03:01:16 -0700 (PDT) Date: Wed, 26 Aug 2020 19:01:13 +0900 From: Sergey Senozhatsky To: John Ogness Cc: Petr Mladek , Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Thomas Gleixner , Peter Zijlstra , Andrea Parri , Paul McKenney , kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 5/7][next] printk: ringbuffer: add finalization/extension support Message-ID: <20200826100113.GA8849@jagdpanzerIV.localdomain> References: <20200824103538.31446-1-john.ogness@linutronix.de> <20200824103538.31446-6-john.ogness@linutronix.de> <87lfi1ls2g.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87lfi1ls2g.fsf@jogness.linutronix.de> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (20/08/26 10:45), John Ogness wrote: > On 2020-08-24, John Ogness wrote: > > @@ -1157,6 +1431,14 @@ bool prb_reserve(struct prb_reserved_entry *e, struct printk_ringbuffer *rb, > > goto fail; > > } > > > > + /* > > + * New data is about to be reserved. Once that happens, previous > > + * descriptors are no longer able to be extended. Finalize the > > + * previous descriptor now so that it can be made available to > > + * readers (when committed). > > + */ > > + desc_finalize(desc_ring, DESC_ID(id - 1)); > > + > > d = to_desc(desc_ring, id); > > > > /* > > Apparently this is not enough to guarantee that past descriptors are > finalized. I am able to reproduce a scenario where the finalization of a > certain descriptor never happens. That leaves the descriptor permanently > in the reserved queried state, which prevents any new records from being > created. I am investigating. Good to know. I also run into problems: - broken dmesg (and broken journalctl -f /dev/kmsg poll) and broken syslog read $ strace dmesg ... openat(AT_FDCWD, "/dev/kmsg", O_RDONLY|O_NONBLOCK) = 3 lseek(3, 0, SEEK_DATA) = 0 read(3, 0x55dda8c240a8, 8191) = -1 EAGAIN (Resource temporarily unavailable) close(3) = 0 syslog(10 /* SYSLOG_ACTION_SIZE_BUFFER */) = 524288 mmap(NULL, 528384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f43ea847000 syslog(3 /* SYSLOG_ACTION_READ_ALL */, "", 524296) = 0 munmap(0x7f43ea847000, 528384) = 0 ... -ss