From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755526AbdKNOcJ (ORCPT ); Tue, 14 Nov 2017 09:32:09 -0500 Received: from mx2.suse.de ([195.135.220.15]:43920 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755483AbdKNOcC (ORCPT ); Tue, 14 Nov 2017 09:32:02 -0500 Date: Tue, 14 Nov 2017 15:32:00 +0100 From: Michal Hocko To: Thomas Gleixner Cc: Andrew Morton , Tejun Heo , Peter Zijlstra , Johannes Weiner , Mel Gorman , linux-mm@kvack.org, LKML Subject: Re: [PATCH] mm: drop hotplug lock from lru_add_drain_all Message-ID: <20171114143200.brmgskoqxjlrhrzx@dhcp22.suse.cz> References: <20171114135348.28704-1-mhocko@kernel.org> <20171114142347.syzyd6tlnpe2afur@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171114142347.syzyd6tlnpe2afur@dhcp22.suse.cz> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 14-11-17 15:23:47, Michal Hocko wrote: [...] > +/* > + * Doesn't need any cpu hotplug locking because we do rely on per-cpu > + * kworkers being shut down before our page_alloc_cpu_dead callback is > + * executed on the offlined cpu > + */ > void lru_add_drain_all(void) > { > static DEFINE_MUTEX(lock); Ble the part of the comment didn't go through diff --git a/mm/swap.c b/mm/swap.c index 8bfdcab9f83e..1ab8122d2d0c 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -688,6 +688,13 @@ static void lru_add_drain_per_cpu(struct work_struct *dummy) static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work); +/* + * Doesn't need any cpu hotplug locking because we do rely on per-cpu + * kworkers being shut down before our page_alloc_cpu_dead callback is + * executed on the offlined cpu. + * Calling this function with cpu hotplug locks held can actually lead + * to obscure indirect dependencies via WQ context. + */ void lru_add_drain_all(void) { static DEFINE_MUTEX(lock); -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id AE7166B0033 for ; Tue, 14 Nov 2017 09:32:02 -0500 (EST) Received: by mail-wm0-f72.google.com with SMTP id b189so2743080wmd.5 for ; Tue, 14 Nov 2017 06:32:02 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id q20si1095257edc.14.2017.11.14.06.32.01 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 14 Nov 2017 06:32:01 -0800 (PST) Date: Tue, 14 Nov 2017 15:32:00 +0100 From: Michal Hocko Subject: Re: [PATCH] mm: drop hotplug lock from lru_add_drain_all Message-ID: <20171114143200.brmgskoqxjlrhrzx@dhcp22.suse.cz> References: <20171114135348.28704-1-mhocko@kernel.org> <20171114142347.syzyd6tlnpe2afur@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171114142347.syzyd6tlnpe2afur@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Thomas Gleixner Cc: Andrew Morton , Tejun Heo , Peter Zijlstra , Johannes Weiner , Mel Gorman , linux-mm@kvack.org, LKML On Tue 14-11-17 15:23:47, Michal Hocko wrote: [...] > +/* > + * Doesn't need any cpu hotplug locking because we do rely on per-cpu > + * kworkers being shut down before our page_alloc_cpu_dead callback is > + * executed on the offlined cpu > + */ > void lru_add_drain_all(void) > { > static DEFINE_MUTEX(lock); Ble the part of the comment didn't go through diff --git a/mm/swap.c b/mm/swap.c index 8bfdcab9f83e..1ab8122d2d0c 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -688,6 +688,13 @@ static void lru_add_drain_per_cpu(struct work_struct *dummy) static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work); +/* + * Doesn't need any cpu hotplug locking because we do rely on per-cpu + * kworkers being shut down before our page_alloc_cpu_dead callback is + * executed on the offlined cpu. + * Calling this function with cpu hotplug locks held can actually lead + * to obscure indirect dependencies via WQ context. + */ void lru_add_drain_all(void) { static DEFINE_MUTEX(lock); -- 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