From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752258AbdGDMwa (ORCPT ); Tue, 4 Jul 2017 08:52:30 -0400 Received: from mx2.suse.de ([195.135.220.15]:58430 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751536AbdGDMw3 (ORCPT ); Tue, 4 Jul 2017 08:52:29 -0400 Date: Tue, 4 Jul 2017 14:52:26 +0200 From: Michal Hocko To: Thomas Gleixner Cc: LKML , linux-mm@kvack.org, Andrey Ryabinin , Andrew Morton , Vlastimil Babka , Vladimir Davydov , Peter Zijlstra Subject: Re: [patch V2 1/2] mm: swap: Provide lru_add_drain_all_cpuslocked() Message-ID: <20170704125226.GP14722@dhcp22.suse.cz> References: <20170704093232.995040438@linutronix.de> <20170704093421.419329357@linutronix.de> <20170704105803.GK14722@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 On Tue 04-07-17 14:48:56, Thomas Gleixner wrote: > On Tue, 4 Jul 2017, Michal Hocko wrote: > > On Tue 04-07-17 11:32:33, Thomas Gleixner wrote: > > > The rework of the cpu hotplug locking unearthed potential deadlocks with > > > the memory hotplug locking code. > > > > > > The solution for these is to rework the memory hotplug locking code as well > > > and take the cpu hotplug lock before the memory hotplug lock in > > > mem_hotplug_begin(), but this will cause a recursive locking of the cpu > > > hotplug lock when the memory hotplug code calls lru_add_drain_all(). > > > > > > Split out the inner workings of lru_add_drain_all() into > > > lru_add_drain_all_cpuslocked() so this function can be invoked from the > > > memory hotplug code with the cpu hotplug lock held. > > > > You have added callers in the later patch in the series AFAICS which > > is OK but I think it would be better to have them in this patch > > already. Nothing earth shattering (maybe a rebase artifact). > > The requirement for changing that comes with the extra hotplug locking in > mem_hotplug_begin(). That is required to establish the proper lock order > and then causes the recursive locking in the next patch. Adding the caller > here would be wrong, because then lru_add_drain_all_cpuslocked() would be > called unprotected. Hens and eggs as usual :) Yeah, you are right. My bad I should have noticed that. -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id E1FD86B0311 for ; Tue, 4 Jul 2017 08:52:29 -0400 (EDT) Received: by mail-wr0-f199.google.com with SMTP id z1so45410468wrz.10 for ; Tue, 04 Jul 2017 05:52:29 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id u10si19392997wmg.100.2017.07.04.05.52.28 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 04 Jul 2017 05:52:28 -0700 (PDT) Date: Tue, 4 Jul 2017 14:52:26 +0200 From: Michal Hocko Subject: Re: [patch V2 1/2] mm: swap: Provide lru_add_drain_all_cpuslocked() Message-ID: <20170704125226.GP14722@dhcp22.suse.cz> References: <20170704093232.995040438@linutronix.de> <20170704093421.419329357@linutronix.de> <20170704105803.GK14722@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Thomas Gleixner Cc: LKML , linux-mm@kvack.org, Andrey Ryabinin , Andrew Morton , Vlastimil Babka , Vladimir Davydov , Peter Zijlstra On Tue 04-07-17 14:48:56, Thomas Gleixner wrote: > On Tue, 4 Jul 2017, Michal Hocko wrote: > > On Tue 04-07-17 11:32:33, Thomas Gleixner wrote: > > > The rework of the cpu hotplug locking unearthed potential deadlocks with > > > the memory hotplug locking code. > > > > > > The solution for these is to rework the memory hotplug locking code as well > > > and take the cpu hotplug lock before the memory hotplug lock in > > > mem_hotplug_begin(), but this will cause a recursive locking of the cpu > > > hotplug lock when the memory hotplug code calls lru_add_drain_all(). > > > > > > Split out the inner workings of lru_add_drain_all() into > > > lru_add_drain_all_cpuslocked() so this function can be invoked from the > > > memory hotplug code with the cpu hotplug lock held. > > > > You have added callers in the later patch in the series AFAICS which > > is OK but I think it would be better to have them in this patch > > already. Nothing earth shattering (maybe a rebase artifact). > > The requirement for changing that comes with the extra hotplug locking in > mem_hotplug_begin(). That is required to establish the proper lock order > and then causes the recursive locking in the next patch. Adding the caller > here would be wrong, because then lru_add_drain_all_cpuslocked() would be > called unprotected. Hens and eggs as usual :) Yeah, you are right. My bad I should have noticed that. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org