Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753608AbdLMQGZ (ORCPT ); Wed, 13 Dec 2017 11:06:25 -0500 Received: from mail-qk0-f170.google.com ([209.85.220.170]:41073 "EHLO mail-qk0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752860AbdLMQGV (ORCPT ); Wed, 13 Dec 2017 11:06:21 -0500 X-Google-Smtp-Source: ACJfBot+H8jId0XK7UKuX8HNAKF2OEUramJx4GuP4BFjzq+i0gVyvztrYBXvo+HU0k12wSjTX38RSQ== Date: Wed, 13 Dec 2017 08:06:17 -0800 From: Tejun Heo To: Prateek Sood Cc: Peter Zijlstra , avagin@gmail.com, mingo@kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, sramana@codeaurora.org Subject: Re: [PATCH] cgroup/cpuset: fix circular locking dependency Message-ID: <20171213160617.GQ3919388@devbig577.frc2.facebook.com> References: <1511868946-23959-1-git-send-email-prsood@codeaurora.org> <623f214b-8b9a-f967-7a3d-ca9c06151267@codeaurora.org> <20171204202219.GF2421075@devbig577.frc2.facebook.com> <20171204225825.GP2421075@devbig577.frc2.facebook.com> <20171204230117.GF20227@worktop.programming.kicks-ass.net> <20171211152059.GH2421075@devbig577.frc2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1135 Lines: 35 Hello, Prateek. On Wed, Dec 13, 2017 at 01:20:46PM +0530, Prateek Sood wrote: > This change makes the usage of cpuset_hotplug_workfn() from cpu > hotplug path synchronous. For memory hotplug it still remains > asynchronous. Ah, right. > Memory migration happening from cpuset_hotplug_workfn() is > already asynchronous by queuing cpuset_migrate_mm_workfn() in > cpuset_migrate_mm_wq. > > cpuset_hotplug_workfn() > cpuset_hotplug_workfn(() > cpuset_migrate_mm() > queue_work(cpuset_migrate_mm_wq) > > It seems that memory migration latency might not have > impact with this change. > > Please let me know if you meant something else by cpuset > migration taking time when memory migration is turned on. No, I didn't. I was just confused about which part became synchronous. So, I don't have anything against making the cpu part synchronous, but let's not do that as the fix to the deadlocks cuz, while we can avoid them by changing cpuset, I don't think cpuset is the root cause for them. If there are benefits to making cpuset cpu migration synchronous, let's do that for those benefits. Thanks. -- tejun