From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:57808 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725973AbeISIpG (ORCPT ); Wed, 19 Sep 2018 04:45:06 -0400 Date: Wed, 19 Sep 2018 11:09:10 +0800 From: Ming Lei To: Tejun Heo Cc: linux-kernel@vger.kernel.org, Jianchao Wang , Kent Overstreet , linux-block@vger.kernel.org Subject: Re: [PATCH 2/4] lib/percpu-refcount: introduce percpu_ref_resurge() Message-ID: <20180919030909.GC20560@ming.t460p> References: <20180918101946.13329-1-ming.lei@redhat.com> <20180918101946.13329-3-ming.lei@redhat.com> <20180918125021.GB902964@devbig004.ftw2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20180918125021.GB902964@devbig004.ftw2.facebook.com> Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org On Tue, Sep 18, 2018 at 05:50:21AM -0700, Tejun Heo wrote: > On Tue, Sep 18, 2018 at 06:19:44PM +0800, Ming Lei wrote: > > Now percpu_ref_reinit() can only be done on one percpu refcounter when it > > drops zero. And the limit shouldn't be so strict, and it is quite > > straightforward that we can do it when the refcount doesn't drop zero > > because it is at atomic mode. > > > > This patch introduces percpu_ref_resurge() in which the above limit is > > relaxed, so we may avoid extra change[1] for NVMe timeout's requirement. > > For now, > > Nacked-by: Tejun Heo > > Please see the original discussion thread. Your comment in that thread supposes that synchronize_rcu() is used for avoiding race with .release(). But this patchset doesn't use that approach at all for avoiding this race. Thanks, Ming