Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755248AbYF3O2k (ORCPT ); Mon, 30 Jun 2008 10:28:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751299AbYF3O23 (ORCPT ); Mon, 30 Jun 2008 10:28:29 -0400 Received: from out1.smtp.messagingengine.com ([66.111.4.25]:35689 "EHLO out1.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751048AbYF3O22 (ORCPT ); Mon, 30 Jun 2008 10:28:28 -0400 X-Sasl-enc: 9JVxR04Gi3isp4MCSB6iFYx9rPtCQz+ltBvk+SHfmF1B 1214836106 Date: Mon, 30 Jun 2008 11:28:22 -0300 From: Henrique de Moraes Holschuh To: Stefan Becker Cc: ext David Brownell , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, ext Alan Stern Subject: Re: PATCH: 2.6.26-rc8: Fix IRQF_DISABLED for shared interrupts Message-ID: <20080630142822.GA22984@khazad-dum.debian.net> References: <200806281251.21299.david-b@pacbell.net> <4867A2DE.3070509@nokia.com> <200806292009.26975.david-b@pacbell.net> <48686D8F.8010901@nokia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <48686D8F.8010901@nokia.com> X-GPG-Fingerprint: 1024D/1CDB0FE3 5422 5C61 F6B7 06FB 7E04 3738 EE25 DE3F 1CDB 0FE3 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1208 Lines: 25 On Mon, 30 Jun 2008, Stefan Becker wrote: > Good question. What happens when you mix a random and a not-so-random > source: does the result have an as good random quality as the original It becomes unusable. In fact, I find it likely that shared IRQs are not safe for random data gathering at all in general. IRQs are not in fact completely random, they just (sometimes) have a very small ammount of randomness in them. And the combined result you see in a shared IRQ line could be correlated or "get somewhat more correlated" because of the sharing (they go over the same BUS -> one can delay the other, etc)... and that correlation might be dangerous. IMO, the safe thing to do is to block shared IRQs from being used as random sources. -- "One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie." -- The Silicon Valley Tarot Henrique Holschuh -- 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/