From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751103AbdAQTHh (ORCPT ); Tue, 17 Jan 2017 14:07:37 -0500 Received: from mail-pg0-f66.google.com ([74.125.83.66]:34589 "EHLO mail-pg0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750849AbdAQTHg (ORCPT ); Tue, 17 Jan 2017 14:07:36 -0500 Date: Tue, 17 Jan 2017 09:02:15 -0800 From: Tejun Heo To: Joonsoo Kim Cc: Vladimir Davydov , cl@linux.com, penberg@kernel.org, rientjes@google.com, akpm@linux-foundation.org, jsvana@fb.com, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 2/9] slab: remove synchronous rcu_barrier() call in memcg cache release path Message-ID: <20170117170215.GC28948@mtj.duckdns.org> References: <20170114055449.11044-1-tj@kernel.org> <20170114055449.11044-3-tj@kernel.org> <20170114131939.GA2668@esperanza> <20170114151921.GA32693@mtj.duckdns.org> <20170117000754.GA25218@js1304-P5Q-DELUXE> <20170117163745.GA8352@mtj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170117163745.GA8352@mtj.duckdns.org> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 17, 2017 at 08:37:45AM -0800, Tejun Heo wrote: > The call sequence doesn't matter. Whether you're using call_rcu() or > rcu_barrier(), you're just waiting for a grace period to pass before > continuing. It doens't give any other ordering guarantees, so the new > code should be equivalent to the old one except for being asynchronous. Oh I was confusing synchronize_rcu() with rcu_barrier(), so you're right, kmem_cache struct needs to stay around for the slab pages to be freed after RCU grace period. Will revise the patch accordingly, thanks. Thanks. -- tejun