From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicholas Mc Guire Subject: Re: [PATCH] migrate_disable pushd down in rt_read_trylock Date: Sun, 15 Dec 2013 15:15:23 +0100 Message-ID: <20131215141522.GA15532@opentech.at> References: <20131123005158.GA16338@opentech.at> <20131129151401.GD31099@linutronix.de> <20131129154425.GE31099@linutronix.de> <20131130023026.GB8114@opentech.at> <20131130064755.GA12036@opentech.at> <20131215131643.GC31090@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-rt-users@vger.kernel.org, Peter Zijlstra , Steven Rostedt , Andreas Platschek To: Sebastian Andrzej Siewior Return-path: Received: from hofr.at ([212.69.189.236]:53976 "EHLO mail.hofr.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754494Ab3LOOPY (ORCPT ); Sun, 15 Dec 2013 09:15:24 -0500 Content-Disposition: inline In-Reply-To: <20131215131643.GC31090@linutronix.de> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Sun, 15 Dec 2013, Sebastian Andrzej Siewior wrote: > * Nicholas Mc Guire | 2013-11-30 07:47:55 [+0100]: > > >given that the broken patch was disabling once and enabling potentially a > >number of times it should have triggert the > >WARN_ON_ONCE(p->migrate_disable <= 0); in migrate_enable() if the recursive > >case would have ever bin hit... so much to testing and locking... > > And is why I removed the line > > No change of functionality > > from the change log because it was not obvious to me that is a > zero-change patch :) well that was the intent and obviously it was not the case - so it served its purpose to document the intent. > > Are you going to redo this one? > no - as David Miller stated clearly that he sees these split-api locks as a valid idiom and there were clear worries that this would break in the future I see no point in pushing this. The alternative of removing the recursive migrate_disable/enable in local_bh_* directly is good enough I guess - see: 0001-make-migrate-disable-enable-conditioned-on-softirq_n.patch thx! hofrat