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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 D560EC34022 for ; Mon, 17 Feb 2020 14:50:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B0F5D20718 for ; Mon, 17 Feb 2020 14:50:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729206AbgBQOuT (ORCPT ); Mon, 17 Feb 2020 09:50:19 -0500 Received: from mx2.suse.de ([195.135.220.15]:37566 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728375AbgBQOuT (ORCPT ); Mon, 17 Feb 2020 09:50:19 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 23A52B47D; Mon, 17 Feb 2020 14:50:17 +0000 (UTC) Date: Mon, 17 Feb 2020 15:50:16 +0100 From: Petr Mladek To: John Ogness Cc: Sergey Senozhatsky , Sergey Senozhatsky , lijiang , Peter Zijlstra , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Andrea Parri , Thomas Gleixner , kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2] printk: replace ringbuffer Message-ID: <20200217145016.7r6b7i5o6tqkaa2x@pathway.suse.cz> References: <20200205044848.GH41358@google.com> <20200205050204.GI41358@google.com> <88827ae2-7af5-347b-29fb-cffb94350f8f@redhat.com> <20200205063640.GJ41358@google.com> <877e11h0ir.fsf@linutronix.de> <20200205110522.GA456@jagdpanzerIV.localdomain> <87wo919grz.fsf@linutronix.de> <20200214155639.m5yp3rd2t3vdzfj7@pathway.suse.cz> <87blpxbh62.fsf@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87blpxbh62.fsf@linutronix.de> User-Agent: NeoMutt/20170912 (1.9.0) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 2020-02-17 12:13:25, John Ogness wrote: > On 2020-02-14, Petr Mladek wrote: > >> I oversaw that devkmsg_open() setup a printk_record and so I did not > >> see to add the extra NULL initialization of text_line_count. There > >> should be be an initializer function/macro to avoid this danger. > >> > >> John Ogness > >> > >> The quick fixup: > >> > >> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c > >> index d0d24ee1d1f4..5ad67ff60cd9 100644 > >> --- a/kernel/printk/printk.c > >> +++ b/kernel/printk/printk.c > >> @@ -883,6 +883,7 @@ static int devkmsg_open(struct inode *inode, struct file *file) > >> user->record.text_buf_size = sizeof(user->text_buf); > >> user->record.dict_buf = &user->dict_buf[0]; > >> user->record.dict_buf_size = sizeof(user->dict_buf); > >> + user->record.text_line_count = NULL; > > > > The NULL pointer hidden in the structure also complicates the code > > reading. It is less obvious when the same function is called > > only to get the size/count and when real data. > > OK. > > > I played with it and created extra function to get this information. > > > > In addition, I had problems to follow the code in > > record_print_text_inline(). So I tried to reuse the new function > > and the existing record_printk_text() there. > > > > Please, find below a patch that I ended with. I booted a system > > with this patch. But I guess that I actually did not use the > > record_print_text_inline(). So, it might be buggy. > > Yes, there are several bugs. But I see where you want to go with this: > > - introduce prb_count_lines() to handle line counting > > - introduce prb_read_valid_info() for only reading meta-data and getting > the line count > > - also use prb_count_lines() internally In addition, I would like share the code between record_print_text_inline() and record_print_text(). They both do very similar thing and the logic in far from trivial. Alternative solution would be to get rid of record_print_text() and use record_print_text_inline() everywhere. It will have some advantages: + _inline() variant will get real testing + no code duplication + saving the extra buffer also in console, sysfs, and devkmsg interface. > I will include these changes in v2. I will still introduce the static > inlines to initialize records because readers and writers do it > differently. Sounds good. Best Regards, Petr