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_INVALID,DKIM_SIGNED, 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 89B7CC31E40 for ; Fri, 9 Aug 2019 06:14:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5373F208C3 for ; Fri, 9 Aug 2019 06:14:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="HFTXmhtz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405536AbfHIGO6 (ORCPT ); Fri, 9 Aug 2019 02:14:58 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:55582 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725920AbfHIGO5 (ORCPT ); Fri, 9 Aug 2019 02:14:57 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=jJMeCIZk1dJ4cGtAjfl9MWzK2vlDx5N7AdKbdBQf0T0=; b=HFTXmhtzNHNKhcj1E06ya8Mrl BwmS0s8MCZYi8hm1k8r27ynoKDjZy21hJ9Qv62FN/QH8G9CBoxK2phV1aWirhubv8dvNiP5sviQ01 +fHnkhey/jRvNTZiJBK1yhL3W/7LZ/zRNuTW6OhkbAl+Ppmywv4y/xCDX4izFbfVfpHnXu62g5kgg ytswo9emvNskg79gNwqALsG2orF3hijRXVKyqT0dKfP8mMc8cqlXE55J4lFt6mRWTbLnws3YRu4jb 6TSHLzYQSkS1dcrss8UCCW6tYXoASNa6xhNGDyzPSgn8b30Fno6K5p9jVtoCJZRTbugYRG9cOLHCI WOVA2eEcQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1hvyAj-00055i-2z; Fri, 09 Aug 2019 06:14:41 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 5A1E2307764; Fri, 9 Aug 2019 08:14:11 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id B38C120BE516F; Fri, 9 Aug 2019 08:14:37 +0200 (CEST) Date: Fri, 9 Aug 2019 08:14:37 +0200 From: Peter Zijlstra To: Linus Torvalds Cc: John Ogness , Linux List Kernel Mailing , Petr Mladek , Sergey Senozhatsky , Steven Rostedt , Greg Kroah-Hartman , Andrea Parri , Thomas Gleixner , Sergey Senozhatsky , Brendan Higgins Subject: Re: [RFC PATCH v4 9/9] printk: use a new ringbuffer implementation Message-ID: <20190809061437.GE2332@hirez.programming.kicks-ass.net> References: <20190807222634.1723-1-john.ogness@linutronix.de> <20190807222634.1723-10-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Thu, Aug 08, 2019 at 12:07:28PM -0700, Linus Torvalds wrote: > End result: a DRAM buffer can work, but is not "reliable". > Particularly if you turn power on and off, data retention of DRAM is > iffy. But it's possible, at least in theory. > > So I have a patch that implements a "stupid ring buffer" for thisa > case, with absolutely zero data structures (because in the presense of > DRAM corruption, all you can get is "hopefully only slightly garbled > ASCII". Note that you can hook this into printk as a fake early serial device; just have the serial device write to the DRAM buffer.