From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751300AbdGQBoY (ORCPT ); Sun, 16 Jul 2017 21:44:24 -0400 Received: from mail-qt0-f182.google.com ([209.85.216.182]:34901 "EHLO mail-qt0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751221AbdGQBoW (ORCPT ); Sun, 16 Jul 2017 21:44:22 -0400 Date: Sun, 16 Jul 2017 21:44:18 -0400 From: Tejun Heo To: cgroups@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Li Zefan , Johannes Weiner , Roman Gushchin , kernel-team@fb.com Subject: [PATCH 2/2 cgroup/for-4.14] cgroup: replace css_set walking populated test with testing cgrp->nr_populated_csets Message-ID: <20170717014418.GB3519177@devbig577.frc2.facebook.com> References: <20170717014333.GA3519177@devbig577.frc2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170717014333.GA3519177@devbig577.frc2.facebook.com> 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 Implement trivial cgroup_has_tasks() which tests whether cgrp->nr_populated_csets is zero and replace the explicit local populated test in cgroup_subtree_control(). This simplifies the code and cgroup_has_tasks() will be used in more places later. Signed-off-by: Tejun Heo --- Applying to cgroup/for-4.14. Thanks. kernel/cgroup/cgroup.c | 30 ++++++++---------------------- 1 file changed, 8 insertions(+), 22 deletions(-) --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -325,6 +325,11 @@ static struct cgroup *cgroup_parent(stru return NULL; } +static bool cgroup_has_tasks(struct cgroup *cgrp) +{ + return cgrp->nr_populated_csets; +} + /* subsystems visibly enabled on a cgroup */ static u16 cgroup_control(struct cgroup *cgrp) { @@ -2971,28 +2976,9 @@ static ssize_t cgroup_subtree_control_wr * Except for the root, subtree_control must be zero for a cgroup * with tasks so that child cgroups don't compete against tasks. */ - if (enable && cgroup_parent(cgrp)) { - struct cgrp_cset_link *link; - - /* - * Because namespaces pin csets too, @cgrp->cset_links - * might not be empty even when @cgrp is empty. Walk and - * verify each cset. - */ - spin_lock_irq(&css_set_lock); - - ret = 0; - list_for_each_entry(link, &cgrp->cset_links, cset_link) { - if (css_set_populated(link->cset)) { - ret = -EBUSY; - break; - } - } - - spin_unlock_irq(&css_set_lock); - - if (ret) - goto out_unlock; + if (enable && cgroup_parent(cgrp) && cgroup_has_tasks(cgrp)) { + ret = -EBUSY; + goto out_unlock; } /* save and update control masks and prepare csses */