From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from merlin.infradead.org ([205.233.59.134]:53078 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762468Ab3DDQjs (ORCPT ); Thu, 4 Apr 2013 12:39:48 -0400 Received: from dhcp-089-099-019-018.chello.nl ([89.99.19.18] helo=dyad.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.80.1 #2 (Red Hat Linux)) id 1UNnCU-0004CW-Tl for linux-media@vger.kernel.org; Thu, 04 Apr 2013 16:39:47 +0000 Message-ID: <1365093584.2609.110.camel@laptop> Subject: Re: [PATCH v2 2/3] mutex: add support for reservation style locks, v2 From: Peter Zijlstra To: Daniel Vetter Cc: Maarten Lankhorst , linux-arch@vger.kernel.org, daniel.vetter@ffwll.ch, x86@kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, robclark@gmail.com, tglx@linutronix.de, mingo@elte.hu, linux-media@vger.kernel.org Date: Thu, 04 Apr 2013 18:39:44 +0200 In-Reply-To: <20130404133123.GW2228@phenom.ffwll.local> References: <20130228102452.15191.22673.stgit@patser> <20130228102502.15191.14146.stgit@patser> <1364900432.18374.24.camel@laptop> <515AF1C1.7080508@canonical.com> <1364921954.20640.22.camel@laptop> <1365076908.2609.94.camel@laptop> <20130404133123.GW2228@phenom.ffwll.local> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On Thu, 2013-04-04 at 15:31 +0200, Daniel Vetter wrote: > The trick with the current code is that the oldest task > will never see an -EAGAIN ever and hence is guaranteed to make forward > progress. If the task is really unlucky though it might be forced to > wait > for a younger task for every ww_mutex it tries to acquire. Agreed on that.. while I didn't state this my proposed thing should behave the same. It follows from the symmetry breaking in that only younger tasks can get 'kill'ed.