Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755283Ab3I2Vez (ORCPT ); Sun, 29 Sep 2013 17:34:55 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.226]:20676 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754843Ab3I2Vew (ORCPT ); Sun, 29 Sep 2013 17:34:52 -0400 Date: Sun, 29 Sep 2013 17:34:47 -0400 From: Steven Rostedt To: Oleg Nesterov Cc: Peter Zijlstra , Mel Gorman , Rik van Riel , Srikar Dronamraju , Ingo Molnar , Andrea Arcangeli , Johannes Weiner , Linux-MM , LKML , Paul McKenney , Thomas Gleixner , Linus Torvalds Subject: Re: [RFC] introduce synchronize_sched_{enter,exit}() Message-ID: <20130929173447.14accc5f@gandalf.local.home> In-Reply-To: <20130929183634.GA15563@redhat.com> References: <1378805550-29949-1-git-send-email-mgorman@suse.de> <1378805550-29949-38-git-send-email-mgorman@suse.de> <20130917143003.GA29354@twins.programming.kicks-ass.net> <20130929183634.GA15563@redhat.com> X-Mailer: Claws Mail 3.9.2 (GTK+ 2.24.20; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.118:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1151 Lines: 29 On Sun, 29 Sep 2013 20:36:34 +0200 Oleg Nesterov wrote: > Why? Say, percpu_rw_semaphore, or upcoming changes in get_online_cpus(), > (Peter, I think they should be unified anyway, but lets ignore this for > now). Or freeze_super() (which currently looks buggy), perhaps something > else. This pattern > Just so I'm clear to what you are trying to implement... This is to handle the case (as Paul said) to see changes to state by RCU and back again? That is, it isn't enough to see that the state changed to something (like SLOW MODE), but we also need a way to see it change back? With get_online_cpus(), we need to see the state where it changed to "performing hotplug" where holders need to go into the slow path, and then also see the state change to "no longe performing hotplug" and the holders now go back to fast path. Is this the rational for this email? Thanks, -- Steve -- 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/