From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: [PATCH 10/16] cgroup: separate out put_css_set_locked() and remove put_css_set_taskexit() Date: Sun, 9 Feb 2014 08:52:38 -0500 Message-ID: <1391953964-22088-11-git-send-email-tj@kernel.org> References: <1391953964-22088-1-git-send-email-tj@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1391953964-22088-1-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org Cc: Tejun Heo , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: containers.vger.kernel.org put_css_set() is performed in two steps - it first tries to put without grabbing css_set_rwsem if such put wouldn't make the count zero. If that fails, it puts after write-locking css_set_rwsem. This patch separates out the second phase into put_css_set_locked() which should be called with css_set_rwsem locked. Also, put_css_set_taskexit() is droped and put_css_set() is made to take @taskexit. There are only a handful users of these functions. No point in providing different variants. put_css_locked() will be used by later changes. This patch doesn't introduce any functional changes. Signed-off-by: Tejun Heo --- kernel/cgroup.c | 50 +++++++++++++++++++++++--------------------------- 1 file changed, 23 insertions(+), 27 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 8c1f840..63d1a4e 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -369,22 +369,14 @@ static unsigned long css_set_hash(struct cgroup_subsys_state *css[]) return key; } -static void __put_css_set(struct css_set *cset, int taskexit) +static void put_css_set_locked(struct css_set *cset, bool taskexit) { struct cgrp_cset_link *link, *tmp_link; - /* - * Ensure that the refcount doesn't hit zero while any readers - * can see it. Similar to atomic_dec_and_lock(), but for an - * rwlock - */ - if (atomic_add_unless(&cset->refcount, -1, 1)) - return; - down_write(&css_set_rwsem); - if (!atomic_dec_and_test(&cset->refcount)) { - up_write(&css_set_rwsem); + lockdep_assert_held(&css_set_rwsem); + + if (!atomic_dec_and_test(&cset->refcount)) return; - } /* This css_set is dead. unlink it and release cgroup refcounts */ hash_del(&cset->hlist); @@ -406,10 +398,24 @@ static void __put_css_set(struct css_set *cset, int taskexit) kfree(link); } - up_write(&css_set_rwsem); kfree_rcu(cset, rcu_head); } +static void put_css_set(struct css_set *cset, bool taskexit) +{ + /* + * Ensure that the refcount doesn't hit zero while any readers + * can see it. Similar to atomic_dec_and_lock(), but for an + * rwlock + */ + if (atomic_add_unless(&cset->refcount, -1, 1)) + return; + + down_write(&css_set_rwsem); + put_css_set_locked(cset, taskexit); + up_write(&css_set_rwsem); +} + /* * refcounted get/put for css_set objects */ @@ -418,16 +424,6 @@ static inline void get_css_set(struct css_set *cset) atomic_inc(&cset->refcount); } -static inline void put_css_set(struct css_set *cset) -{ - __put_css_set(cset, 0); -} - -static inline void put_css_set_taskexit(struct css_set *cset) -{ - __put_css_set(cset, 1); -} - /** * compare_css_sets - helper function for find_existing_css_set(). * @cset: candidate css_set being tested @@ -1751,7 +1747,7 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp, * we're safe to drop it here; it will be freed under RCU. */ set_bit(CGRP_RELEASABLE, &old_cgrp->flags); - put_css_set(old_cset); + put_css_set(old_cset, false); } /** @@ -1897,7 +1893,7 @@ out_put_css_set_refs: tc = flex_array_get(group, i); if (!tc->cset) break; - put_css_set(tc->cset); + put_css_set(tc->cset, false); } } out_cancel_attach: @@ -3714,7 +3710,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) /* * css_set_rwsem synchronizes access to ->cset_links and prevents - * @cgrp from being removed while __put_css_set() is in progress. + * @cgrp from being removed while put_css_set() is in progress. */ down_read(&css_set_rwsem); empty = list_empty(&cgrp->cset_links); @@ -4266,7 +4262,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks) } task_unlock(tsk); - put_css_set_taskexit(cset); + put_css_set(cset, true); } static void check_for_release(struct cgroup *cgrp) -- 1.8.5.3 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752661AbaBINzM (ORCPT ); Sun, 9 Feb 2014 08:55:12 -0500 Received: from mail-qa0-f54.google.com ([209.85.216.54]:56489 "EHLO mail-qa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752369AbaBINxL (ORCPT ); Sun, 9 Feb 2014 08:53:11 -0500 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 10/16] cgroup: separate out put_css_set_locked() and remove put_css_set_taskexit() Date: Sun, 9 Feb 2014 08:52:38 -0500 Message-Id: <1391953964-22088-11-git-send-email-tj@kernel.org> X-Mailer: git-send-email 1.8.5.3 In-Reply-To: <1391953964-22088-1-git-send-email-tj@kernel.org> References: <1391953964-22088-1-git-send-email-tj@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org put_css_set() is performed in two steps - it first tries to put without grabbing css_set_rwsem if such put wouldn't make the count zero. If that fails, it puts after write-locking css_set_rwsem. This patch separates out the second phase into put_css_set_locked() which should be called with css_set_rwsem locked. Also, put_css_set_taskexit() is droped and put_css_set() is made to take @taskexit. There are only a handful users of these functions. No point in providing different variants. put_css_locked() will be used by later changes. This patch doesn't introduce any functional changes. Signed-off-by: Tejun Heo --- kernel/cgroup.c | 50 +++++++++++++++++++++++--------------------------- 1 file changed, 23 insertions(+), 27 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 8c1f840..63d1a4e 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -369,22 +369,14 @@ static unsigned long css_set_hash(struct cgroup_subsys_state *css[]) return key; } -static void __put_css_set(struct css_set *cset, int taskexit) +static void put_css_set_locked(struct css_set *cset, bool taskexit) { struct cgrp_cset_link *link, *tmp_link; - /* - * Ensure that the refcount doesn't hit zero while any readers - * can see it. Similar to atomic_dec_and_lock(), but for an - * rwlock - */ - if (atomic_add_unless(&cset->refcount, -1, 1)) - return; - down_write(&css_set_rwsem); - if (!atomic_dec_and_test(&cset->refcount)) { - up_write(&css_set_rwsem); + lockdep_assert_held(&css_set_rwsem); + + if (!atomic_dec_and_test(&cset->refcount)) return; - } /* This css_set is dead. unlink it and release cgroup refcounts */ hash_del(&cset->hlist); @@ -406,10 +398,24 @@ static void __put_css_set(struct css_set *cset, int taskexit) kfree(link); } - up_write(&css_set_rwsem); kfree_rcu(cset, rcu_head); } +static void put_css_set(struct css_set *cset, bool taskexit) +{ + /* + * Ensure that the refcount doesn't hit zero while any readers + * can see it. Similar to atomic_dec_and_lock(), but for an + * rwlock + */ + if (atomic_add_unless(&cset->refcount, -1, 1)) + return; + + down_write(&css_set_rwsem); + put_css_set_locked(cset, taskexit); + up_write(&css_set_rwsem); +} + /* * refcounted get/put for css_set objects */ @@ -418,16 +424,6 @@ static inline void get_css_set(struct css_set *cset) atomic_inc(&cset->refcount); } -static inline void put_css_set(struct css_set *cset) -{ - __put_css_set(cset, 0); -} - -static inline void put_css_set_taskexit(struct css_set *cset) -{ - __put_css_set(cset, 1); -} - /** * compare_css_sets - helper function for find_existing_css_set(). * @cset: candidate css_set being tested @@ -1751,7 +1747,7 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp, * we're safe to drop it here; it will be freed under RCU. */ set_bit(CGRP_RELEASABLE, &old_cgrp->flags); - put_css_set(old_cset); + put_css_set(old_cset, false); } /** @@ -1897,7 +1893,7 @@ out_put_css_set_refs: tc = flex_array_get(group, i); if (!tc->cset) break; - put_css_set(tc->cset); + put_css_set(tc->cset, false); } } out_cancel_attach: @@ -3714,7 +3710,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) /* * css_set_rwsem synchronizes access to ->cset_links and prevents - * @cgrp from being removed while __put_css_set() is in progress. + * @cgrp from being removed while put_css_set() is in progress. */ down_read(&css_set_rwsem); empty = list_empty(&cgrp->cset_links); @@ -4266,7 +4262,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks) } task_unlock(tsk); - put_css_set_taskexit(cset); + put_css_set(cset, true); } static void check_for_release(struct cgroup *cgrp) -- 1.8.5.3