From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0C92C3A59F for ; Mon, 26 Aug 2019 15:25:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B23242173E for ; Mon, 26 Aug 2019 15:25:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731441AbfHZPZ0 (ORCPT ); Mon, 26 Aug 2019 11:25:26 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:40486 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727658AbfHZPZ0 (ORCPT ); Mon, 26 Aug 2019 11:25:26 -0400 Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1i2Grz-0007W4-Hf; Mon, 26 Aug 2019 17:25:23 +0200 Date: Mon, 26 Aug 2019 17:25:23 +0200 From: Sebastian Andrzej Siewior To: Joel Fernandes Cc: Scott Wood , linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, "Paul E . McKenney" , Thomas Gleixner , Peter Zijlstra , Juri Lelli , Clark Williams Subject: Re: [PATCH RT v2 2/3] sched: migrate_enable: Use sleeping_lock to indicate involuntary sleep Message-ID: <20190826152523.dcjbsgyyir4zjdol@linutronix.de> References: <20190821231906.4224-1-swood@redhat.com> <20190821231906.4224-3-swood@redhat.com> <20190823162024.47t7br6ecfclzgkw@linutronix.de> <433936e4c720e6b81f9b297fefaa592fd8a961ad.camel@redhat.com> <20190824031014.GB2731@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190824031014.GB2731@google.com> User-Agent: NeoMutt/20180716 Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On 2019-08-23 23:10:14 [-0400], Joel Fernandes wrote: > On Fri, Aug 23, 2019 at 02:28:46PM -0500, Scott Wood wrote: > > On Fri, 2019-08-23 at 18:20 +0200, Sebastian Andrzej Siewior wrote: > > > > > > this looks like an ugly hack. This sleeping_lock_inc() is used where we > > > actually hold a sleeping lock and schedule() which is okay. But this > > > would mean we hold a RCU lock and schedule() anyway. Is that okay? > > > > Perhaps the name should be changed, but the concept is the same -- RT- > > specific sleeping which should be considered involuntary for the purpose of > > debug checks. Voluntary sleeping is not allowed in an RCU critical section > > because it will break the critical section on certain flavors of RCU, but > > that doesn't apply to the flavor used on RT. Sleeping for a long time in an > > RCU critical section would also be a bad thing, but that also doesn't apply > > here. > > I think the name should definitely be changed. At best, it is super confusing to > call it "sleeping_lock" for this scenario. In fact here, you are not even > blocking on a lock. > > Maybe "sleeping_allowed" or some such. The mechanism that is used here may change in future. I just wanted to make sure that from RCU's side it is okay to schedule here. > thanks, > > - Joel Sebastian