Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756542Ab2KHTHV (ORCPT ); Thu, 8 Nov 2012 14:07:21 -0500 Received: from mail-pb0-f46.google.com ([209.85.160.46]:37830 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752222Ab2KHTHU (ORCPT ); Thu, 8 Nov 2012 14:07:20 -0500 Date: Thu, 8 Nov 2012 11:07:15 -0800 From: Tejun Heo To: lizefan@huawei.com, mhocko@suse.cz, rjw@sisk.pl Cc: containers@lists.linux-foundation.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, fweisbec@gmail.com, Glauber Costa Subject: [PATCH 1/9 v3] cgroup: add cgroup_subsys->post_create() Message-ID: <20121108190715.GD9672@htj.dyndns.org> References: <1351931915-1701-1-git-send-email-tj@kernel.org> <1351931915-1701-2-git-send-email-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1351931915-1701-2-git-send-email-tj@kernel.org> 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 Content-Length: 3150 Lines: 94 Subject: cgroup: add cgroup_subsys->post_create() Currently, there's no way for a controller to find out whether a new cgroup finished all ->create() allocatinos successfully and is considered "live" by cgroup. This becomes a problem later when we add generic descendants walking to cgroup which can be used by controllers as controllers don't have a synchronization point where it can synchronize against new cgroups appearing in such walks. This patch adds ->post_create(). It's called after all ->create() succeeded and the cgroup is linked into the generic cgroup hierarchy. This plays the counterpart of ->pre_destroy(). When used in combination with the to-be-added generic descendant iterators, ->post_create() can be used to implement reliable state inheritance. It will be explained with the descendant iterators. v2: Added a paragraph about its future use w/ descendant iterators per Michal. v3: Forgot to add ->post_create() invocation to cgroup_load_subsys(). Fixed. Signed-off-by: Tejun Heo Acked-by: Michal Hocko Reviewed-by: KAMEZAWA Hiroyuki Cc: Glauber Costa --- Oops, forgot updating cgroup_load_subsys(). Hate that it's a different path from cgroup_init_subsys(). :( Thanks. include/linux/cgroup.h | 1 + kernel/cgroup.c | 15 +++++++++++++-- 2 files changed, 14 insertions(+), 2 deletions(-) --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -438,6 +438,7 @@ int cgroup_taskset_size(struct cgroup_ta struct cgroup_subsys { struct cgroup_subsys_state *(*create)(struct cgroup *cgrp); + void (*post_create)(struct cgroup *cgrp); void (*pre_destroy)(struct cgroup *cgrp); void (*destroy)(struct cgroup *cgrp); int (*can_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset); --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4059,10 +4059,15 @@ static long cgroup_create(struct cgroup if (err < 0) goto err_remove; - /* each css holds a ref to the cgroup's dentry */ - for_each_subsys(root, ss) + for_each_subsys(root, ss) { + /* each css holds a ref to the cgroup's dentry */ dget(dentry); + /* creation succeeded, notify subsystems */ + if (ss->post_create) + ss->post_create(cgrp); + } + /* The cgroup directory was pre-locked for us */ BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex)); @@ -4280,6 +4285,9 @@ static void __init cgroup_init_subsys(st ss->active = 1; + if (ss->post_create) + ss->post_create(&ss->root->top_cgroup); + /* this function shouldn't be used with modular subsystems, since they * need to register a subsys_id, among other things */ BUG_ON(ss->module); @@ -4389,6 +4397,9 @@ int __init_or_module cgroup_load_subsys( ss->active = 1; + if (ss->post_create) + ss->post_create(&ss->root->top_cgroup); + /* success! */ mutex_unlock(&cgroup_mutex); return 0; -- 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/