Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756839Ab3E0IAo (ORCPT ); Mon, 27 May 2013 04:00:44 -0400 Received: from merlin.infradead.org ([205.233.59.134]:36609 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754364Ab3E0IAm (ORCPT ); Mon, 27 May 2013 04:00:42 -0400 Date: Mon, 27 May 2013 10:00:19 +0200 From: Peter Zijlstra To: Maarten Lankhorst Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, x86@kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, robclark@gmail.com, rostedt@goodmis.org, tglx@linutronix.de, mingo@elte.hu, linux-media@vger.kernel.org, Dave Airlie Subject: Re: [PATCH v3 2/3] mutex: add support for wound/wait style locks, v3 Message-ID: <20130527080019.GD2781@laptop> References: <20130428165914.17075.57751.stgit@patser> <20130428170407.17075.80082.stgit@patser> <20130430191422.GA5763@phenom.ffwll.local> <519CA976.9000109@canonical.com> <20130522161831.GQ18810@twins.programming.kicks-ass.net> <519CFF56.90600@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <519CFF56.90600@canonical.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1179 Lines: 22 On Wed, May 22, 2013 at 07:24:38PM +0200, Maarten Lankhorst wrote: > >> +- Functions to only acquire a single w/w mutex, which results in the exact same > >> + semantics as a normal mutex. These functions have the _single postfix. > > This is missing rationale. > trylock_single is useful when iterating over a list, and you want to evict a bo, but only the first one that can be acquired. > lock_single is useful when only a single bo needs to be acquired, for example to lock a buffer during mmap. OK, so given that its still early, monday and I haven't actually spend much time thinking on this; would it be possible to make: ww_mutex_lock(.ctx=NULL) act like ww_mutex_lock_single()? The idea is that if we don't provide a ctx, we'll get a different lockdep annotation; mutex_lock() vs mutex_lock_nest_lock(). So if we then go and make a mistake, lockdep should warn us. Would that work or should I stock up on morning juice? -- 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/