From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755672Ab3H1VFo (ORCPT ); Wed, 28 Aug 2013 17:05:44 -0400 Received: from mail-qa0-f48.google.com ([209.85.216.48]:51641 "EHLO mail-qa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752197Ab3H1VD7 (ORCPT ); Wed, 28 Aug 2013 17:03:59 -0400 From: Tejun Heo To: lizefan@huawei.com Cc: containers@lists.linux-foundation.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Tejun Heo Subject: [PATCH 3/9] cgroup: make for_each_subsys() useable under cgroup_root_mutex Date: Wed, 28 Aug 2013 17:03:43 -0400 Message-Id: <1377723829-22814-4-git-send-email-tj@kernel.org> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1377723829-22814-1-git-send-email-tj@kernel.org> References: <1377723829-22814-1-git-send-email-tj@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We want to use for_each_subsys() in cgroupfs_root handling where only cgroup_root_mutex is held. The only way cgroup_subsys[] can change is through module load/unload, make cgroup_[un]load_subsys() grab cgroup_root_mutex too and update the lockdep annotation in for_each_subsys() to allow either cgroup_mutex or cgroup_root_mutex. * Lockdep annotation is moved from inner 'if' condition to outer 'for' init caluse. There's no reason to execute the assertion every loop. * Loop index @i is renamed to @ssid. Indices iterating through subsys will be [re]named to @ssid gradually. Signed-off-by: Tejun Heo --- kernel/cgroup.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index a10baf8..a65be0c 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -291,14 +291,17 @@ static int notify_on_release(const struct cgroup *cgrp) /** * for_each_subsys - iterate all loaded cgroup subsystems * @ss: the iteration cursor - * @i: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end + * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end * - * Should be called under cgroup_mutex. + * Iterates through all loaded subsystems. Should be called under + * cgroup_mutex or cgroup_root_mutex. */ -#define for_each_subsys(ss, i) \ - for ((i) = 0; (i) < CGROUP_SUBSYS_COUNT; (i)++) \ - if (({ lockdep_assert_held(&cgroup_mutex); \ - !((ss) = cgroup_subsys[i]); })) { } \ +#define for_each_subsys(ss, ssid) \ + for (({ WARN_ON_ONCE(debug_locks && \ + (!lockdep_is_held(&cgroup_mutex) && \ + !lockdep_is_held(&cgroup_root_mutex))); \ + (ssid) = 0; }); (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \ + if (!((ss) = cgroup_subsys[(ssid)])) { } \ else /** @@ -4911,6 +4914,7 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss) cgroup_init_cftsets(ss); mutex_lock(&cgroup_mutex); + mutex_lock(&cgroup_root_mutex); cgroup_subsys[ss->subsys_id] = ss; /* @@ -4966,10 +4970,12 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss) goto err_unload; /* success! */ + mutex_unlock(&cgroup_root_mutex); mutex_unlock(&cgroup_mutex); return 0; err_unload: + mutex_unlock(&cgroup_root_mutex); mutex_unlock(&cgroup_mutex); /* @ss can't be mounted here as try_module_get() would fail */ cgroup_unload_subsys(ss); @@ -4999,6 +5005,7 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss) BUG_ON(ss->root != &cgroup_dummy_root); mutex_lock(&cgroup_mutex); + mutex_lock(&cgroup_root_mutex); offline_css(cgroup_css(cgroup_dummy_top, ss)); @@ -5037,6 +5044,7 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss) ss->css_free(cgroup_css(cgroup_dummy_top, ss)); RCU_INIT_POINTER(cgroup_dummy_top->subsys[ss->subsys_id], NULL); + mutex_unlock(&cgroup_root_mutex); mutex_unlock(&cgroup_mutex); } EXPORT_SYMBOL_GPL(cgroup_unload_subsys); -- 1.8.3.1