From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753907Ab3BDKNh (ORCPT ); Mon, 4 Feb 2013 05:13:37 -0500 Received: from shutemov.name ([204.155.152.216]:37786 "EHLO shutemov.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751023Ab3BDKNf (ORCPT ); Mon, 4 Feb 2013 05:13:35 -0500 Date: Mon, 4 Feb 2013 12:15:21 +0200 From: "Kirill A. Shutemov" To: Li Zefan Cc: Tejun Heo , LKML , Cgroups , Davide Libenzi , Aaron Durbin , Greg Thelen Subject: Re: [PATCH 1/4] eventfd: introduce eventfd_signal_hangup() Message-ID: <20130204101521.GA18322@shutemov.name> References: <510CB733.2080904@huawei.com> <510CB744.7000300@huawei.com> <20130202155858.GA13022@shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130202155858.GA13022@shutemov.name> 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 On Sat, Feb 02, 2013 at 05:58:58PM +0200, Kirill A. Shutemov wrote: > On Sat, Feb 02, 2013 at 02:50:44PM +0800, Li Zefan wrote: > > When an eventfd is closed, a wakeup with POLLHUP will be issued, > > but cgroup wants to issue wakeup explicitly, so when a cgroup is > > removed userspace can be notified. > > > > Signed-off-by: Li Zefan Hm.. Looks like it will break eventfd semantics: 1. One eventfd can be used for deliver more then one notification from one or more cgroups. POLLHUP on removing one of cgroups is not valid. 2. It's valid to have eventfd opened only by one userspace application. We should not close it, just because cgroup is removed. I think problem with multiple threads waiting an event on eventfd should be handled in userspace. -- Kirill A. Shutemov