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[209.85.167.42]) by smtp.gmail.com with ESMTPSA id f23sm1179992lfc.25.2019.08.09.09.00.21 for (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Fri, 09 Aug 2019 09:00:21 -0700 (PDT) Received: by mail-lf1-f42.google.com with SMTP id x3so69985552lfc.0 for ; Fri, 09 Aug 2019 09:00:21 -0700 (PDT) X-Received: by 2002:a19:641a:: with SMTP id y26mr12874406lfb.29.1565366420690; Fri, 09 Aug 2019 09:00:20 -0700 (PDT) MIME-Version: 1.0 References: <20190807222634.1723-1-john.ogness@linutronix.de> <20190807222634.1723-10-john.ogness@linutronix.de> <874l2rclmw.fsf@linutronix.de> <20190808194523.6f83e087@gandalf.local.home> <20190808204841.5afcad46@gandalf.local.home> In-Reply-To: From: Linus Torvalds Date: Fri, 9 Aug 2019 09:00:04 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH v4 9/9] printk: use a new ringbuffer implementation To: Thomas Gleixner Cc: Steven Rostedt , John Ogness , Linux List Kernel Mailing , Peter Zijlstra , Petr Mladek , Sergey Senozhatsky , Greg Kroah-Hartman , Andrea Parri , Sergey Senozhatsky , Brendan Higgins Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 9, 2019 at 4:15 AM Thomas Gleixner wrote: > > > > > But I don't know what a power-off-in-laptop scenario really looks like.. > > That's random behaviour. It's hardware & BIOS & value add. What do you > expect? > > I tried on a few machines. My laptop does not retain any useful information > and on some server box (which takes ages to boot) the memory is squeaky > clean, i.e. the BIOS wiped it already. Some others worked with a two second > delay between turning the remote power switch on and off. You were there at the Intel meeting, weren't you? This is all about the fact that "we're not getting sane and reliable debug facilities for remote debugging". We haven't gotten them over two decades, we're not seeing it in the future either. So what if we _can_ get an ACPI update and in the next decade your laptop _will_ have a memory area that doesn't get scribbled over? Does it work today? Yes it does, but only for very special cases (basically warm reboot with "fast boot" enabled). But they are special cases that may be things that can be extended upon without any actual hardware changes. Linus