From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755234AbaCMTuV (ORCPT ); Thu, 13 Mar 2014 15:50:21 -0400 Received: from mail-qc0-f175.google.com ([209.85.216.175]:41987 "EHLO mail-qc0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754936AbaCMTuS (ORCPT ); Thu, 13 Mar 2014 15:50:18 -0400 From: Tejun Heo To: lizefan@huawei.com Cc: cgroups@vger.kernel.org, containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Tejun Heo Subject: [PATCH 01/11] cgroup: cgroup->subsys[] should be cleared after the css is offlined Date: Thu, 13 Mar 2014 15:50:03 -0400 Message-Id: <1394740213-17626-2-git-send-email-tj@kernel.org> X-Mailer: git-send-email 1.8.5.3 In-Reply-To: <1394740213-17626-1-git-send-email-tj@kernel.org> References: <1394740213-17626-1-git-send-email-tj@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org After a css finishes offlining, offline_css() mistakenly performs RCU_INIT_POINTER(css->cgroup->subsys[ss->id], css) which just sets the cgroup->subsys[] pointer to the current value. The intention was to clear it after offline is complete, not reassign the same value. Update it to assign NULL instead of the current value. This makes cgroup_css() to return NULL once offline is complete. All the existing users of the function either can handle NULL return already or guarantee that the css doesn't get offlined. While this is a bugfix, as css lifetime is currently tied to the cgroup it belongs to, this bug doesn't cause any actual problems. Signed-off-by: Tejun Heo --- kernel/cgroup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 306ad0e..ca19735 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -3535,7 +3535,7 @@ static void offline_css(struct cgroup_subsys_state *css) css->flags &= ~CSS_ONLINE; css->cgroup->nr_css--; - RCU_INIT_POINTER(css->cgroup->subsys[ss->id], css); + RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL); } /** -- 1.8.5.3