Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756503AbZFWHJL (ORCPT ); Tue, 23 Jun 2009 03:09:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751666AbZFWHJD (ORCPT ); Tue, 23 Jun 2009 03:09:03 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:57743 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751559AbZFWHJB (ORCPT ); Tue, 23 Jun 2009 03:09:01 -0400 Date: Tue, 23 Jun 2009 16:07:20 +0900 From: KAMEZAWA Hiroyuki To: "linux-mm@kvack.org" Cc: "linux-kernel@vger.kernel.org" , "nishimura@mxp.nes.nec.co.jp" , "balbir@linux.vnet.ibm.com" , "lizf@cn.fujitsu.com" , "menage@google.com" , "akpm@linux-foundation.org" Subject: [PATCH 0/2] memcg: cgroup fix rmdir hang Message-Id: <20090623160720.36230fa2.kamezawa.hiroyu@jp.fujitsu.com> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 2.5.0 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1236 Lines: 44 previous discussion was this => http://marc.info/?t=124478543600001&r=1&w=2 This patch tries to fix problem as - rmdir can sleep very very long if swap entry is shared between multiple cgroups Now, cgroup's rmdir path does following == again: check there are no tasks and children group. call pre_destroy() check css's refcnt if (refcnt > 0) { sleep until css's refcnt goes down to 0. goto again } == Unfortunately, memory cgroup does following at charge. css_get(&memcg->css) .... charge(memcg) (increase USAGE) ... And this "memcg" is not necessary to include the caller, task. pre_destroy() tries to reduce memory usage until USAGE goes down to 0. Then, there is a race that - css's refcnt > 0 (and memcg's usage > 0) - rmdir() caller sleeps until css->refcnt goes down 0. - But to make css->refcnt be 0, pre_destroy() should be called again. This patch tries to fix this in asyhcnrounos way (i.e. without big lock.) Any comments are welcome. Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/