From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: [PATCH 4/6] cgroup: use RCU free in create_css() failure path Date: Thu, 24 Apr 2014 17:02:11 -0400 Message-ID: <1398373333-1521-5-git-send-email-tj@kernel.org> References: <1398373333-1521-1-git-send-email-tj@kernel.org> Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references; bh=WcKS5ZOeu0dFl8sHIiukImOzHrBCddnljrVDHDzCEVc=; b=Rpdz62TIE7Rft/rXwJrJ2/m9R1IAPb/Q7cDSrx10G8phxaHx7f5GS3sPKyDVGdSM8I q8fy2mTnk67g8huGieoww2QjtexoYbUD5MbOTn9QNqAJI11iy6l+Z4Jfej+siibd6QME UL9kdAH1AqviQymlNBiWc+Pz5BlrMirvoT4FlfpvGd+SUijBfjogoWWsp1KwQet49Hzr 2zfFuqGgavUfM0nRzyIn4aLgP/R07UUg+KkdKso1Yj1rohomUmdEyiU3alXEoaj8X+ls aOUGvRgZ3k2EHYZotr55PeYRy3vryKQy86CRsa2jFE6CAcKkDGvfFJMJRHwbuk0cSVU1 0lIQ== In-Reply-To: <1398373333-1521-1-git-send-email-tj@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lizefan@huawei.com Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, hannes@cmpxchg.org, mhocko@suse.cz, nasa4836@gmail.com, Tejun Heo Currently, when create_css() fails in the middle, the half-initialized css is freed by invoking cgroup_subsys->css_free() directly. This patch updates the function so that it invokes RCU free path instead. As the RCU free path puts the parent css and owning cgroup, their references are now acquired right after a new css is successfully allocated. This doesn't make any visible difference now but is to enable implementing css->id and RCU protected lookup by such IDs. Signed-off-by: Tejun Heo --- kernel/cgroup.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 7cb9c08..0e2c401 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4185,12 +4185,14 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss) if (IS_ERR(css)) return PTR_ERR(css); + init_css(css, ss, cgrp); + cgroup_get(cgrp); + css_get(css->parent); + err = percpu_ref_init(&css->refcnt, css_release); if (err) goto err_free_css; - init_css(css, ss, cgrp); - err = cgroup_populate_dir(cgrp, 1 << ss->id); if (err) goto err_free_percpu_ref; @@ -4199,9 +4201,6 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss) if (err) goto err_clear_dir; - cgroup_get(cgrp); - css_get(css->parent); - if (ss->broken_hierarchy && !ss->warned_broken_hierarchy && parent->parent) { pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n", @@ -4218,7 +4217,7 @@ err_clear_dir: err_free_percpu_ref: percpu_ref_cancel_init(&css->refcnt); err_free_css: - ss->css_free(css); + call_rcu(&css->rcu_head, css_free_rcu_fn); return err; } -- 1.9.0