From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752366AbdFUVmV (ORCPT ); Wed, 21 Jun 2017 17:42:21 -0400 Received: from mail-yw0-f196.google.com ([209.85.161.196]:35489 "EHLO mail-yw0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751487AbdFUVmT (ORCPT ); Wed, 21 Jun 2017 17:42:19 -0400 Date: Wed, 21 Jun 2017 17:42:16 -0400 From: Tejun Heo To: Waiman Long Cc: Li Zefan , Johannes Weiner , Peter Zijlstra , Ingo Molnar , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, pjt@google.com, luto@amacapital.net, efault@gmx.de, torvalds@linux-foundation.org Subject: Re: [RFC PATCH-cgroup 5/6] cgroup: Skip dying css in cgroup_apply_control_{enable,disable} Message-ID: <20170621214216.GE14720@htj.duckdns.org> References: <1497452737-11125-1-git-send-email-longman@redhat.com> <1497452737-11125-6-git-send-email-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1497452737-11125-6-git-send-email-longman@redhat.com> User-Agent: Mutt/1.8.2 (2017-04-18) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Wed, Jun 14, 2017 at 11:05:36AM -0400, Waiman Long wrote: > While constantly turning on and off controllers, it is possible to > trigger the dying CSS warnings in cgroup_apply_control_enable() and > cgroup_apply_control_disable(). The current code, however, proceeds > after the warning leading to other secondary warnings and maybe even > data corruption, like > > cgroup: cgroup_addrm_files: failed to add current, err=-17 > > To avoid the secondary errors, the dying CSS is now ignored or skipped > so as not to cause other problem. > > Signed-off-by: Waiman Long > --- > kernel/cgroup/cgroup.c | 20 +++++++++++++++----- > 1 file changed, 15 insertions(+), 5 deletions(-) > > diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c > index f0bea32..2a5bd49 100644 > --- a/kernel/cgroup/cgroup.c > +++ b/kernel/cgroup/cgroup.c > @@ -2846,12 +2846,24 @@ static int cgroup_apply_control_enable(struct cgroup *cgrp) > for_each_subsys(ss, ssid) { > struct cgroup_subsys_state *css = cgroup_css(dsct, ss); > > - WARN_ON_ONCE(css && percpu_ref_is_dying(&css->refcnt)); > - > if (!(cgroup_ss_mask(dsct, false) & (1 << ss->id)) || > (dsct->bypass_ss_mask & (1 << ss->id))) > continue; > > + /* > + * If the css is dying, we will just skip it after > + * warning. > + */ > + if (css && (css->flags & CSS_DYING)) { > + char name[NAME_MAX+1]; > + > + cgroup_name(cgrp, name, NAME_MAX); > + pr_warn("%s: %s css of cgroup %s is dying!\n", > + __func__, ss->name, name); > + WARN_ON_ONCE(1); > + continue; > + } Can you trigger this without your patches because this triggering means that the code screwed up before it reached this point. We should be fixing that bug rather than masking it up here. Thanks. -- tejun