From owner-freebsd-arch@FreeBSD.ORG Fri Feb 27 15:21:22 2015 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 2D658402 for ; Fri, 27 Feb 2015 15:21:22 +0000 (UTC) Received: from bigwig.baldwin.cx (bigwig.baldwin.cx [IPv6:2001:470:1f11:75::1]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 07033A5B for ; Fri, 27 Feb 2015 15:21:22 +0000 (UTC) Received: from ralph.baldwin.cx (pool-173-54-116-245.nwrknj.fios.verizon.net [173.54.116.245]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id 1E4B9B960; Fri, 27 Feb 2015 10:21:21 -0500 (EST) From: John Baldwin To: freebsd-arch@freebsd.org Subject: Re: Minor ULE changes and optimizations Date: Fri, 27 Feb 2015 09:14:10 -0500 Message-ID: <2311645.BNIPBaFv2E@ralph.baldwin.cx> User-Agent: KMail/4.14.2 (FreeBSD/10.1-STABLE; KDE/4.14.2; amd64; ; ) In-Reply-To: <54EF2C54.7030207@astrodoggroup.com> References: <54EF2C54.7030207@astrodoggroup.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Fri, 27 Feb 2015 10:21:21 -0500 (EST) Cc: Harrison Grundy X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 27 Feb 2015 15:21:22 -0000 On Thursday, February 26, 2015 06:23:16 AM Harrison Grundy wrote: > https://reviews.freebsd.org/D1969 > This allows a non-migratable thread to pin itself to a CPU if it is > already running on that CPU. > > I've been running these patches for the past week or so without issue. > Any additional testing or comments would be greatly appreciated. Can you explain the reason / use case for this? This seems to be allowing an API violation. sched_pin() was designed to be a lower-level API than sched_bind(), so you wouldn't call sched_bind() if you were already pinned. In addition, sched_pin() is sometimes used by code that assumes it won't migrate until sched_unpin() (e.g. temporary mappings inside an sfbuf). If you allow sched_bind() to move a thread that is pinned you will allow someone to unintentionally break those sort of things instead of getting an assertion failure panic. -- John Baldwin