From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755858Ab0DCSLp (ORCPT ); Sat, 3 Apr 2010 14:11:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:12961 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755075Ab0DCSLj (ORCPT ); Sat, 3 Apr 2010 14:11:39 -0400 Message-ID: <4BB7822F.1000100@third-harmonic.com> Date: Sat, 03 Apr 2010 14:00:15 -0400 From: john cooper User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Darren Hart CC: "Peter W. Morreale" , rostedt@goodmis.org, "lkml," , Peter Zijlstra , Gregory Haskins , Sven-Thorsten Dietrich , Thomas Gleixner , Ingo Molnar , Eric Dumazet , Chris Mason , john cooper Subject: Re: RFC: Ideal Adaptive Spinning Conditions References: <4BB3D90C.3030108@us.ibm.com> <1270078689.19685.8040.camel@gandalf.stny.rr.com> <1270081066.2997.22.camel@hermosa.site> <4BB4041C.6020302@us.ibm.com> In-Reply-To: <4BB4041C.6020302@us.ibm.com> X-Enigmail-Version: 0.96.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Darren Hart wrote: > Right, and I'm looking to provide some kernel assistance for userspace > spinlocks here, and am targeting short lived critical sections as well. What did you have in mind beyond existing mechanisms which address sibling contention? One scenario which AFAICT isn't yet addressed is that of a userspace spin lock holder taking a scheduling preemption which may result in other threads piling up on the lock orders of magnitude beyond normal wait times, until the lock holder is rescheduled. -john -- john.cooper@third-harmonic.com