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=-5.1 required=3.0 tests=BUG6152_INVALID_DATE_TZ_ABSURD,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS,INVALID_DATE_TZ_ABSURD,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 46026C433E0 for ; Thu, 9 Jul 2020 07:03:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 18D5E2065D for ; Thu, 9 Jul 2020 07:03:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="YxVpPnUM"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="TWsmltBc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726321AbgGIHDo (ORCPT ); Thu, 9 Jul 2020 03:03:44 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:33022 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726140AbgGIHDo (ORCPT ); Thu, 9 Jul 2020 03:03:44 -0400 From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1594278222; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=b094mquuzsSv4LF1uZkVaKAu65Nvlb3yg5Y2rgetvew=; b=YxVpPnUMWW4M+ckySVPwnqBLPQAXP016ktzDOSgX8oNn0pBLjg0MJaFhSiH1c0nHqSSSdD NeqCk9ylTuciVG+UX7a5SykXAuqNBVHEKWuSE3HyKhQvJwHEqNtdJQeUDpnilr9fb/s8hG klu9I89PX5PzxjTNlXkvdtBbi/kVbiDvRBxyHmeuTVEtOQAK+Wvrx2azj/0etXfBeJAupa EIAs5Udhe7RhXN/WM9SlkHD0vKo8tiogzWsV02zwPgS0+1PjYC7/iyfrz0iPHckwlEXoQ0 uroTd8dzJoS5kC7a0ftoaWTRkofUtGAPPFD2+ESs8BdlhPn2czpU3TAmmDPPWA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1594278222; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=b094mquuzsSv4LF1uZkVaKAu65Nvlb3yg5Y2rgetvew=; b=TWsmltBcjmai5IXExwbUPLpMSO6iux3fbPrn3VWNrZt/gq8jwf9v2v1v7GCgZ55VwTacdn RYgSVEC+VXjoiVAw== To: Petr Mladek Cc: Peter Zijlstra , Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Andrea Parri , Thomas Gleixner , Paul McKenney , kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 0/4] printk: replace ringbuffer In-Reply-To: <20200708152005.GF4751@alley> References: <20200707145932.8752-1-john.ogness@linutronix.de> <20200708152005.GF4751@alley> Date: Thu, 09 Jul 2020 09:09:31 +0206 Message-ID: <87wo3d9nlo.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-07-08, Petr Mladek wrote: > OK, I think that we are ready to try this in linux-next. > I am going to push it there via printk/linux.git. > > [...] > > Of course, there are still many potential problems. The following comes > to my mind: > > [...] > > + Debugging tools accessing the buffer directly would need to > understand the new structure. Fortunately John provided > patches for the most prominent ones. The next series in the printk-rework (move LOG_CONT handling from writers to readers) makes some further changes that, while not incompatible, could affect the output of existing tools. It may be a good idea to let the new ringbuffer sit in linux-next until the next series has been discussed/reviewed/merged. After the next series, everything will be in place (with regard to userspace tools) to finish the rework. As reminder, here are all the steps planned for the full rework: 1. replace ringbuffer 2. implement NMI-safe LOG_CONT (i.e. move handling to readers) 3. remove logbuf_lock 4. remove safe buffers 5. implement per-console printing kthreads 6. implement emergency mode and write_atomic() support 7. implement write_atomic() for 8250 UART Some of the steps may be combined into a single series if the changes are not too dramatic. John Ogness