From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753285AbbCJSVT (ORCPT ); Tue, 10 Mar 2015 14:21:19 -0400 Received: from mblankhorst.nl ([141.105.120.124]:41498 "EHLO mblankhorst.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751231AbbCJSVQ (ORCPT ); Tue, 10 Mar 2015 14:21:16 -0400 Message-ID: <54FF3616.8060004@canonical.com> Date: Tue, 10 Mar 2015 19:21:10 +0100 From: Maarten Lankhorst User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Peter Zijlstra CC: Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org, Ingo Molnar , Mike Galbraith Subject: Re: [PATCH 2/3] locking: ww_mutex: Allow to use rt_mutex instead of mutex for the baselock References: <1425056229-22326-1-git-send-email-bigeasy@linutronix.de> <1425056229-22326-3-git-send-email-bigeasy@linutronix.de> <20150310123740.GA2896@worktop.programming.kicks-ass.net> <54FEFB66.1070606@canonical.com> <20150310152826.GE2896@worktop.programming.kicks-ass.net> In-Reply-To: <20150310152826.GE2896@worktop.programming.kicks-ass.net> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hey, Op 10-03-15 om 16:28 schreef Peter Zijlstra: > On Tue, Mar 10, 2015 at 03:10:46PM +0100, Maarten Lankhorst wrote: >> Op 10-03-15 om 13:37 schreef Peter Zijlstra: > >>> So IIRC this is the function that checks who gets wounded (and gets to >>> do the whole retry thing), right? >>> >>> So for the RT case, I think we should extend it to not (primarily) be a >>> FIFO thing, but also consider the priority of the tasks involved. >>> >>> Maybe a little something like: >>> >>> if (hold_ctx->task->prio < ctx->task->prio) >>> return -EDEADLOCK; >>> >>> before the timestamp check; although I suppose we should also add a >>> deadline test in case both prios are -1. > >> I think that's useful but if you implement -EDEADLK based on thread >> priority, any boosted thread should receive -EDEADLK when it tries to >> acquire a new lock in the same context, to force it to back off.. > > But _only_ if the boost comes from inside the ww_ctx, right? > > Yeah, implementing that might be tricky, maybe we can keep it as a note > for now ;) Indeed! ~Maarten