Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756832Ab2KZRey (ORCPT ); Mon, 26 Nov 2012 12:34:54 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:47958 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933674Ab2KZRMQ (ORCPT ); Mon, 26 Nov 2012 12:12:16 -0500 From: Herton Ronaldo Krzesinski To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Tejun Heo , Frederic Weisbecker , Herton Ronaldo Krzesinski Subject: [PATCH 198/270] Revert "cgroup: Remove task_lock() from cgroup_post_fork()" Date: Mon, 26 Nov 2012 14:58:08 -0200 Message-Id: <1353949160-26803-199-git-send-email-herton.krzesinski@canonical.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1353949160-26803-1-git-send-email-herton.krzesinski@canonical.com> References: <1353949160-26803-1-git-send-email-herton.krzesinski@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2216 Lines: 66 3.5.7u1 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Tejun Heo commit d87838321124061f6c935069d97f37010fa417e6 upstream. This reverts commit 7e3aa30ac8c904a706518b725c451bb486daaae9. The commit incorrectly assumed that fork path always performed threadgroup_change_begin/end() and depended on that for synchronization against task exit and cgroup migration paths instead of explicitly grabbing task_lock(). threadgroup_change is not locked when forking a new process (as opposed to a new thread in the same process) and even if it were it wouldn't be effective as different processes use different threadgroup locks. Revert the incorrect optimization. Signed-off-by: Tejun Heo LKML-Reference: <20121008020000.GB2575@localhost> Acked-by: Li Zefan Cc: Frederic Weisbecker Signed-off-by: Herton Ronaldo Krzesinski --- kernel/cgroup.c | 15 +++------------ 1 file changed, 3 insertions(+), 12 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 75d4318..a91aa0b 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4805,19 +4805,10 @@ void cgroup_post_fork(struct task_struct *child) */ if (use_task_css_set_links) { write_lock(&css_set_lock); - if (list_empty(&child->cg_list)) { - /* - * It's safe to use child->cgroups without task_lock() - * here because we are protected through - * threadgroup_change_begin() against concurrent - * css_set change in cgroup_task_migrate(). Also - * the task can't exit at that point until - * wake_up_new_task() is called, so we are protected - * against cgroup_exit() setting child->cgroup to - * init_css_set. - */ + task_lock(child); + if (list_empty(&child->cg_list)) list_add(&child->cg_list, &child->cgroups->tasks); - } + task_unlock(child); write_unlock(&css_set_lock); } } -- 1.7.9.5 -- 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/