From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936225AbaFIJXV (ORCPT ); Mon, 9 Jun 2014 05:23:21 -0400 Received: from ns.horizon.com ([71.41.210.147]:37581 "HELO ns.horizon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S933541AbaFIJXS (ORCPT ); Mon, 9 Jun 2014 05:23:18 -0400 Date: 9 Jun 2014 05:23:17 -0400 Message-ID: <20140609092317.17828.qmail@ns.horizon.com> From: "George Spelvin" To: linux@horizon.com, tytso@mit.edu Subject: Re: [RFC PATCH] drivers/char/random.c: Is reducing locking range like this safe? Cc: hpa@linux.intel.com, linux-kernel@vger.kernel.org, mingo@kernel.org, price@mit.edu In-Reply-To: <20140609040355.8126.qmail@ns.horizon.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Sigh, adventures in "unable to mount root filesystem" currently underway. PEBKAC resolved. (I had CONFIG_ATA=m for some testing, but forgot to change it back to y when compiling a kernel I expected to boot.) 32 MiB write: Without patch With patch 0 readers: 0.495523 0.494998 0.515995 0.516026 1 reader: 0.842245 0.845308 0.704283 0.704318 2 readers: 1.18658 1.18762 0.904635 0.904844 3 readers: 1.49615 1.49616 1.14311 1.16836 I haven't rebooted back to the without-patch kernel to see if the 20 ms loss is consistent, but obviously that needs fixing. (There's more than just that patch I posted in there.) Anyway, it's noticeable, but maybe not worth fixing. The interesting question is whether we should get rid of out[]. That's obscurity that contributes no security, and thus a Bad Thing by definition.