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authorMandeep Singh Baines <msb@chromium.org>2011-12-21 20:18:35 -0800
committerTejun Heo <tj@kernel.org>2011-12-22 07:32:57 -0800
commit026085ef5ae07c3197f2baacc091ce067b86ed11 (patch)
tree0497b6414f79efff5b1ba855ddae70a2d850a2b4 /kernel/cgroup.c
parentc84cdf75ccb2845f690579e838f13f7e744e3d23 (diff)
cgroup: remove redundant get/put of old css_set from migrate
We can now assume that the css_set reference held by the task will not go away for an exiting task. PF_EXITING state can be trusted throughout migration by checking it after locking threadgroup. Changes in V4: * https://lkml.org/lkml/2011/12/20/368 (Tejun Heo) * Fix typo in commit message * Undid the rename of css_set_check_fetched * https://lkml.org/lkml/2011/12/20/427 (Li Zefan) * Fix comment in cgroup_task_migrate() Changes in V3: * https://lkml.org/lkml/2011/12/20/255 (Frederic Weisbecker) * Fixed to put error in retval Changes in V2: * https://lkml.org/lkml/2011/12/19/289 (Tejun Heo) * Updated commit message -tj: removed stale patch description about dropped function rename. Signed-off-by: Mandeep Singh Baines <msb@chromium.org> Acked-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org> Cc: containers@lists.linux-foundation.org Cc: cgroups@vger.kernel.org Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Paul Menage <paul@paulmenage.org>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c28
1 files changed, 8 insertions, 20 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 4936d8886b4..82288088f6a 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1850,14 +1850,12 @@ static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
struct css_set *newcg;
/*
- * get old css_set. We are synchronized through threadgroup_lock()
- * against PF_EXITING setting such that we can't race against
- * cgroup_exit() changing the css_set to init_css_set and dropping the
- * old one.
+ * We are synchronized through threadgroup_lock() against PF_EXITING
+ * setting such that we can't race against cgroup_exit() changing the
+ * css_set to init_css_set and dropping the old one.
*/
WARN_ON_ONCE(tsk->flags & PF_EXITING);
oldcg = tsk->cgroups;
- get_css_set(oldcg);
/* locate or allocate a new css_set for this task. */
if (guarantee) {
@@ -1872,12 +1870,9 @@ static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
might_sleep();
/* find_css_set will give us newcg already referenced. */
newcg = find_css_set(oldcg, cgrp);
- if (!newcg) {
- put_css_set(oldcg);
+ if (!newcg)
return -ENOMEM;
- }
}
- put_css_set(oldcg);
task_lock(tsk);
rcu_assign_pointer(tsk->cgroups, newcg);
@@ -2186,18 +2181,11 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
* init_css_set.
*/
oldcg = tc->task->cgroups;
- get_css_set(oldcg);
- /* see if the new one for us is already in the list? */
- if (css_set_check_fetched(cgrp, tc->task, oldcg, &newcg_list)) {
- /* was already there, nothing to do. */
- put_css_set(oldcg);
- } else {
- /* we don't already have it. get new one. */
- retval = css_set_prefetch(cgrp, oldcg, &newcg_list);
- put_css_set(oldcg);
- if (retval)
+
+ /* if we don't already have it in the list get a new one */
+ if (!css_set_check_fetched(cgrp, tc->task, oldcg, &newcg_list))
+ if (retval = css_set_prefetch(cgrp, oldcg, &newcg_list))
goto out_list_teardown;
- }
}
/*