From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753340Ab1LTXPb (ORCPT ); Tue, 20 Dec 2011 18:15:31 -0500 Received: from mail-ey0-f202.google.com ([209.85.215.202]:51047 "EHLO mail-ey0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753119Ab1LTXOo (ORCPT ); Tue, 20 Dec 2011 18:14:44 -0500 From: Mandeep Singh Baines To: Tejun Heo , Li Zefan , LKML , Frederic Weisbecker Cc: Mandeep Singh Baines , Tejun Heo , Li Zefan , containers@lists.linux-foundation.org, cgroups@vger.kernel.org, KAMEZAWA Hiroyuki , Frederic Weisbecker , Oleg Nesterov , Andrew Morton , Paul Menage Subject: [PATCH 2/5] cgroup: remove redundant get/put of task struct Date: Tue, 20 Dec 2011 15:14:30 -0800 Message-Id: <1324422873-31001-3-git-send-email-msb@chromium.org> X-Mailer: git-send-email 1.7.3.1 In-Reply-To: <1324422873-31001-1-git-send-email-msb@chromium.org> References: <1324422873-31001-1-git-send-email-msb@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org threadgroup_lock() guarantees that the target threadgroup will remain stable - no new task will be added, no new PF_EXITING will be set and exec won't happen. Signed-off-by: Mandeep Singh Baines Cc: Tejun Heo Cc: Li Zefan Cc: containers@lists.linux-foundation.org Cc: cgroups@vger.kernel.org Cc: KAMEZAWA Hiroyuki Cc: Frederic Weisbecker Cc: Oleg Nesterov Cc: Andrew Morton Cc: Paul Menage --- kernel/cgroup.c | 12 +----------- 1 files changed, 1 insertions(+), 11 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 4166066..6649529 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2130,7 +2130,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) /* as per above, nr_threads may decrease, but not increase. */ BUG_ON(i >= group_size); - get_task_struct(tsk); /* * saying GFP_ATOMIC has no effect here because we did prealloc * earlier, but it's good form to communicate our expectations. @@ -2152,7 +2151,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) /* methods shouldn't be called if no task is actually migrating */ retval = 0; if (!nr_migrating_tasks) - goto out_put_tasks; + goto out_free_group_list; /* * step 1: check that we can legitimately attach to the cgroup. @@ -2233,12 +2232,6 @@ out_cancel_attach: ss->cancel_attach(ss, cgrp, &tset); } } -out_put_tasks: - /* clean up the array of referenced threads in the group. */ - for (i = 0; i < group_size; i++) { - tc = flex_array_get(group, i); - put_task_struct(tc->task); - } out_free_group_list: flex_array_free(group); return retval; @@ -2287,14 +2280,12 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup) cgroup_unlock(); return -EACCES; } - get_task_struct(tsk); rcu_read_unlock(); } else { if (threadgroup) tsk = current->group_leader; else tsk = current; - get_task_struct(tsk); } threadgroup_lock(tsk); @@ -2306,7 +2297,6 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup) threadgroup_unlock(tsk); - put_task_struct(tsk); cgroup_unlock(); return ret; } -- 1.7.3.1