From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751681AbaHDHzl (ORCPT ); Mon, 4 Aug 2014 03:55:41 -0400 Received: from casper.infradead.org ([85.118.1.10]:60873 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751206AbaHDHzj (ORCPT ); Mon, 4 Aug 2014 03:55:39 -0400 Date: Mon, 4 Aug 2014 09:55:28 +0200 From: Peter Zijlstra To: Waiman Long Cc: Ingo Molnar , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, Davidlohr Bueso , Jason Low , Scott J Norton Subject: Re: [PATCH 1/7] locking/rwsem: don't resched at the end of optimistic spinning Message-ID: <20140804075528.GI9918@twins.programming.kicks-ass.net> References: <1407119782-41119-1-git-send-email-Waiman.Long@hp.com> <1407119782-41119-2-git-send-email-Waiman.Long@hp.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="vzhXYRv6YJrvJIA1" Content-Disposition: inline In-Reply-To: <1407119782-41119-2-git-send-email-Waiman.Long@hp.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 --vzhXYRv6YJrvJIA1 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, Aug 03, 2014 at 10:36:16PM -0400, Waiman Long wrote: > For a fully preemptive kernel, a call to preempt_enable() could > potentially trigger a task rescheduling event. In the case of rwsem > optimistic spinning, the task has either gotten the lock or is going > to sleep soon. So there is no point to do rescheduling here. Uh what? Why shouldn't we preempt if we've gotten the lock? What if a FIFO task just woke up?=20 --vzhXYRv6YJrvJIA1 Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJT3zxwAAoJEHZH4aRLwOS6RYMP/RKT7ZtZg1Gg4KJhJJHMgXcg SbnhqX5QJdJxu4KZ9w9KqmODKp6zUdBUI1Y70Qg/Xhafrkqcpt2qnfShfITQGaVk smm1gje+0ZAZzQeW01Hj1bZcj6WIRVoFVcXMsNvO+bamtyI4oOrGlSOggo8XI6+h NZW8YZClw4Ui5qy+OiOCBToU41XI/eUka7Y5QTU3FR5cNL4W0e0TMCmgSlfleIWt J20HdykK7arBfOGew1DQ3/Uau/lAb1X+YZIWtYes1g76wLXAoteGVOHCsGoeNk6o 5SsPVq9diI33wd4jseZ/3co87R2gPxabmmQLFQOnhMgI/wdisKux4GTv1FWyENsW +IfeF2ZvssuYvcT6fyGWncuosNeQTMlf9r4b/xDzr47f3xugQaLv3KPy2QowVTEG jVTuNyh2sKs8V9EWgdzpTzrk5XaIudoqnAwYHYNkh22zYv/5pTogScSMWPEFd9ZT KH808BZ4A0B/wsbeqhf23MRyPv7f049bg4V7sq/lWdxDB9OvSUa+hPnKKBd1FYde e+jllWEE33X4iDuxBY41bUOGOIuuMTPdFe7qlCe25PWUF8hLe8us9w/UF1ra6xHD ByzdJDvCa6PxknJmRNayQOR8iSNkQ/7QFpnS7dyMRpU49DWwjgAG9QIpwYVTpWQu vuIEWMl/YIvIiqJi5Kuy =upai -----END PGP SIGNATURE----- --vzhXYRv6YJrvJIA1--