From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753104Ab1KQWFe (ORCPT ); Thu, 17 Nov 2011 17:05:34 -0500 Received: from e8.ny.us.ibm.com ([32.97.182.138]:60477 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752334Ab1KQWFd (ORCPT ); Thu, 17 Nov 2011 17:05:33 -0500 Message-ID: <1321567402.25715.35.camel@work-vm> Subject: Re: [PATCH 15/16] time: Update tiemkeeper structure using a local shadow From: John Stultz To: LKML Cc: Thomas Gleixner , Eric Dumazet , Richard Cochran Date: Thu, 17 Nov 2011 14:03:22 -0800 In-Reply-To: <1321329846-14755-16-git-send-email-john.stultz@linaro.org> References: <1321329846-14755-1-git-send-email-john.stultz@linaro.org> <1321329846-14755-16-git-send-email-john.stultz@linaro.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.1- Content-Transfer-Encoding: 7bit Mime-Version: 1.0 x-cbid: 11111722-9360-0000-0000-000000B5C909 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2011-11-14 at 20:04 -0800, John Stultz wrote: > Uses a local shadow structure to update the timekeeper. This > reduces the timekeeper.lock hold time. > > WARNING: This introduces a race, but the window might be provably > so small as to not be observable. This patch needs lots more math > and comments to validate that assumption. Bah. After thinking about it, this patch won't work, since it would possibly lose updates via settimeofday(), etc. So I'm coming around to Thomas' double lock reader-seq/writer-lock method. thanks -john