Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754609AbaD1JJw (ORCPT ); Mon, 28 Apr 2014 05:09:52 -0400 Received: from mail-ee0-f51.google.com ([74.125.83.51]:62298 "EHLO mail-ee0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754573AbaD1JJu (ORCPT ); Mon, 28 Apr 2014 05:09:50 -0400 Message-ID: <1398676186.30930.49.camel@marge.simpson.net> Subject: Re: [ANNOUNCE] 3.14-rt1 From: Mike Galbraith To: Nicholas Mc Guire Cc: Sebastian Andrzej Siewior , linux-rt-users , LKML , Thomas Gleixner , rostedt@goodmis.org, John Kacur Date: Mon, 28 Apr 2014 11:09:46 +0200 In-Reply-To: <1398661784.30930.33.camel@marge.simpson.net> References: <20140411185739.GA6644@linutronix.de> <1397918766.5436.16.camel@marge.simpson.net> <1398411635.11930.45.camel@marge.simpson.net> <1398501491.12941.5.camel@marge.simpson.net> <1398520699.28726.22.camel@marge.simpson.net> <1398661784.30930.33.camel@marge.simpson.net> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2014-04-28 at 07:09 +0200, Mike Galbraith wrote: > Hi Nicholas, > > On Sat, 2014-04-26 at 15:58 +0200, Mike Galbraith wrote: > > On Sat, 2014-04-26 at 10:38 +0200, Mike Galbraith wrote: > > > On Fri, 2014-04-25 at 09:40 +0200, Mike Galbraith wrote: > > > > > > > Hotplug can still deadlock in rt trees too, and will if you beat it > > > > hard. > > > > > > Box actually deadlocks like so. > > > > ... > > > > 3.12-rt looks a bit busted migrate_disable/enable() wise. > > > > /me eyeballs 3.10-rt (looks better), confirms 3.10-rt hotplug works, > > swipes working code, confirms 3.12-rt now works. Yup, that was it. > > My boxen, including 64 core DL980 that ran hotplug stress for 3 hours > yesterday with pre-pushdown rwlocks, say the migrate_disable/enable > pushdown patches are very definitely busted. migrate_disable-pushd-down-in-atomic_dec_and_spin_lo.patch bug: migrate_disable() after blocking is too late. @@ -1028,12 +1028,12 @@ int atomic_dec_and_spin_lock(atomic_t *a /* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */ if (atomic_add_unless(atomic, -1, 1)) return 0; - migrate_disable(); rt_spin_lock(lock); - if (atomic_dec_and_test(atomic)) + if (atomic_dec_and_test(atomic)){ + migrate_disable(); return 1; + } rt_spin_unlock(lock); - migrate_enable(); return 0; } EXPORT_SYMBOL(atomic_dec_and_spin_lock); read_lock-migrate_disable-pushdown-to-rt_read_lock.patch bug: ditto. @@ -244,8 +246,10 @@ void __lockfunc rt_read_lock(rwlock_t *r /* * recursive read locks succeed when current owns the lock */ - if (rt_mutex_owner(lock) != current) + if (rt_mutex_owner(lock) != current) { __rt_spin_lock(lock); + migrate_disable(); + } rwlock->read_depth++; } Moving that migrate_disable() up will likely fix my hotplug troubles. I'll find out when I get back from physical torture (therapy) session. -Mike -- 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/