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Subject[PATCH 06/16] cgroup: reimplement cgroup_transfer_tasks() without using css_scan_tasks()
Date
Reimplement cgroup_transfer_tasks() so that it repeatedly fetches the
first task in the cgroup and then tranfers it. This achieves the same
result without using css_scan_tasks() which is scheduled to be
removed.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/cgroup.c | 31 ++++++++++++++++++++-----------
1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 96a3a85..a5f965c 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2849,15 +2849,6 @@ int css_scan_tasks(struct cgroup_subsys_state *css,
return 0;
}

-static void cgroup_transfer_one_task(struct task_struct *task, void *data)
-{
- struct cgroup *new_cgroup = data;
-
- mutex_lock(&cgroup_mutex);
- cgroup_attach_task(new_cgroup, task, false);
- mutex_unlock(&cgroup_mutex);
-}
-
/**
* cgroup_trasnsfer_tasks - move tasks from one cgroup to another
* @to: cgroup to which the tasks will be moved
@@ -2865,8 +2856,26 @@ static void cgroup_transfer_one_task(struct task_struct *task, void *data)
*/
int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
{
- return css_scan_tasks(&from->dummy_css, NULL, cgroup_transfer_one_task,
- to, NULL);
+ struct css_task_iter it;
+ struct task_struct *task;
+ int ret = 0;
+
+ do {
+ css_task_iter_start(&from->dummy_css, &it);
+ task = css_task_iter_next(&it);
+ if (task)
+ get_task_struct(task);
+ css_task_iter_end(&it);
+
+ if (task) {
+ mutex_lock(&cgroup_mutex);
+ ret = cgroup_attach_task(to, task, false);
+ mutex_unlock(&cgroup_mutex);
+ put_task_struct(task);
+ }
+ } while (task && !ret);
+
+ return ret;
}

/*
--
1.8.5.3


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