From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752969AbZIXPx7 (ORCPT ); Thu, 24 Sep 2009 11:53:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752308AbZIXPx6 (ORCPT ); Thu, 24 Sep 2009 11:53:58 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45724 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751932AbZIXPx6 (ORCPT ); Thu, 24 Sep 2009 11:53:58 -0400 Date: Thu, 24 Sep 2009 19:57:32 +0200 From: Stanislaw Gruszka To: Peter Zijlstra Cc: Thomas Gleixner , Ingo Molnar , Oleg Nesterov , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] itimers: fix racy writes to cpu_itimer fields Message-ID: <20090924195732.384bea26@dhcp-lab-109.englab.brq.redhat.com> In-Reply-To: <1253803687.18939.26.camel@laptop> References: <1253802903-979-1-git-send-email-sgruszka@redhat.com> <1253803687.18939.26.camel@laptop> Organization: RedHat Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 24 Sep 2009 16:48:07 +0200 Peter Zijlstra wrote: > On Thu, 2009-09-24 at 16:35 +0200, Stanislaw Gruszka wrote: > > incr_error and error fields of struct cpu_itimer are used when calculating > > next timer tick in check_cpu_itimers() and should not be modified without > > tsk->sighand->siglock taken. > > Won't it be all-round much better to convert these things to hrtimers > instead of adding more and more fuzz on top to make them deal with > jiffies? Perhaps it would, but I don't know how to do it :{ . Especially how to precisely account user time. The only idea I have is make something like microstate accounting (http://lwn.net/Articles/127296/), but this patch and whole idea was rejected long time ago. Stanislaw