Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758647AbZDEVt5 (ORCPT ); Sun, 5 Apr 2009 17:49:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755570AbZDEVtp (ORCPT ); Sun, 5 Apr 2009 17:49:45 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:34081 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758296AbZDEVto (ORCPT ); Sun, 5 Apr 2009 17:49:44 -0400 Message-ID: <49D92773.8030306@us.ibm.com> Date: Sun, 05 Apr 2009 14:49:39 -0700 From: Darren Hart User-Agent: Thunderbird 2.0.0.21 (X11/20090318) MIME-Version: 1.0 To: Thomas Gleixner CC: linux-kernel@vger.kernel.org, Sripathi Kodi , Peter Zijlstra , John Stultz , Steven Rostedt , Dinakar Guniguntala , Ulrich Drepper , Eric Dumazet , Ingo Molnar , Jakub Jelinek Subject: Re: [tip PATCH v7 0/9] RFC: futex: requeue pi implementation References: <20090403203832.9772.21410.stgit@Aeon> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2372 Lines: 49 Thomas Gleixner wrote: > Darren, > > On Fri, 3 Apr 2009, Darren Hart wrote: >> The following series is v7 of the requeue_pi patches against >> linux-2.6-tip/core/futexes. The current futex implementation doesn't allow for >> requeueing of PI futexes, which leads to a thundering herd during >> pthread_cond_broadcasa()t (as opposed to a civilized priority ordered wakeup >> sequence). The core of the problem is that the underlying rt_mutex cannot be >> left with waiters and no owner (which would break the PI logic). This patch >> series updates the futex code to allow for requeueing from non-PI to PI futexes >> in support of PI aware pthread_cond_* calls along with some needful rt_mutex >> helper routines. The credit for the conceptual design goes to Thomas Gleixner, >> while the bugs and other idiocies present in this implementation should be >> attributed to me. > > I went through the patches with a fine comb again and there is nothing > left which triggered my futex wreckage sensors. Thanks for your > patience to go through the lather, rinse, repeat drill. > > I think we are at a point where that code simply needs exposure to the > hostile environment of RT-Java VMs. I'm going to pull that into > tip/next and into -rt. Even if we have no requeue_pi user right now we > definitly want to test the heck out of the changes which also affect > the existing futex ops. > > Uli, Jakub can you please go over the design and the user space > interface ? > > Darren, could you please polish the initial design notes - especially > point out the subtle differences between requeue and requeue_pi - and > send them into the thread? That might help Uli and Jakub and we > definitly want to have that info preserved in Documentation/ as well. > Thanks Thomas! I'll review and update the docs (the emails you sent me last year along with git commit messages for these patches) and send out a new requeue_pi design and implementation document that we can consider for inclusion in Documentation/. I'll try and have something out on Monday. -- Darren Hart IBM Linux Technology Center Real-Time Linux Team -- 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/