From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752572AbbJSHGL (ORCPT ); Mon, 19 Oct 2015 03:06:11 -0400 Received: from mail-wi0-f174.google.com ([209.85.212.174]:33115 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750912AbbJSHGK (ORCPT ); Mon, 19 Oct 2015 03:06:10 -0400 Date: Mon, 19 Oct 2015 09:06:05 +0200 From: Ingo Molnar To: Peter Zijlstra Cc: Catalin Marinas , "Paul E. McKenney" , Will Deacon , Linux Kernel Mailing List , Oleg Nesterov , Linus Torvalds , Andrew Morton Subject: Re: Q: schedule() and implied barriers on arm64 Message-ID: <20151019070604.GA17855@gmail.com> References: <20151016151830.GZ3816@twins.programming.kicks-ass.net> <20151016160422.GQ3910@linux.vnet.ibm.com> <20151016161608.GA3816@twins.programming.kicks-ass.net> <20151016190648.GC3816@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151016190648.GC3816@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra wrote: > In any case, its all moot now, since Paul no longer requires schedule() to imply > a full barrier. > > [...] Nevertheless from a least-surprise POV it might be worth guaranteeing it, because I bet there's tons of code that assumes that schedule() is a heavy operation and it's such an easy mistake to make. Since we are so close to having that guarantee, we might as well codify it? Just like system calls are assumed to be barriers in general - and system calls are more lightweight than schedule() ... Thanks, Ingo