Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754681AbaBDQkA (ORCPT ); Tue, 4 Feb 2014 11:40:00 -0500 Received: from order.stressinduktion.org ([87.106.68.36]:57585 "EHLO order.stressinduktion.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753612AbaBDQj6 (ORCPT ); Tue, 4 Feb 2014 11:39:58 -0500 Date: Tue, 4 Feb 2014 17:39:57 +0100 From: Hannes Frederic Sowa To: Stephan Mueller Cc: Geert Uytterhoeven , "Theodore Ts'o" , =?utf-8?B?SsO2cm4=?= Engel , "H. Peter Anvin" , Linux Kernel Developers List , "Maciej W. Rozycki" , Ralf Baechle , dave.taht@gmail.com, John Crispin , andrewmcgr@gmail.com, Thorsten Glaser , sandyinchina@gmail.com Subject: Re: [PATCH 2/5] CPU Jitter RNG: Enable compilation Message-ID: <20140204163957.GA13928@order.stressinduktion.org> Mail-Followup-To: Stephan Mueller , Geert Uytterhoeven , Theodore Ts'o , =?utf-8?B?SsO2cm4=?= Engel , "H. Peter Anvin" , Linux Kernel Developers List , "Maciej W. Rozycki" , Ralf Baechle , dave.taht@gmail.com, John Crispin , andrewmcgr@gmail.com, Thorsten Glaser , sandyinchina@gmail.com References: <2039634.jSmQAS6tdi@myon.chronox.de> <3180926.X9oRPa7ARL@myon.chronox.de> <3579180.ti4z33qfDe@tauon> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <3579180.ti4z33qfDe@tauon> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 04, 2014 at 05:19:52PM +0100, Stephan Mueller wrote: > Also, I consider the execution speed of the entropy collection is not > really an issue because the RNG delivers random numbers at a > comparatively high rate. Any other noise source feeding into random.c > delivers data with far less speed. Compiling the kernel with -O0 could add some other problems, like e.g. not doing enough constant folding which could result in linking errors. I guess it is not a problem currently though, but some of the compile time checks depend on this (compiletime_assert and such). Have you looked into adding compiler barriers into relevant places in the loops to stop the compiler from optimizing and spill out the values from the registers to their memory locations? Greetings, Hannes -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/