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cgroup, cpuset: replace move_member_tasks_to_cpuset() with cgroup_transfer_tasks()

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When a cpuset becomes empty (no CPU or memory), its tasks are
transferred with the nearest ancestor with execution resources.  This
is implemented using cgroup_scan_tasks() with a callback which grabs
cgroup_mutex and invokes cgroup_attach_task() on each task.

Both cgroup_mutex and cgroup_attach_task() are scheduled to be
unexported.  Implement cgroup_transfer_tasks() in cgroup proper which
is essentially the same as move_member_tasks_to_cpuset() except that
it takes cgroups instead of cpusets and @to comes before @from like
normal functions with those arguments, and replace
move_member_tasks_to_cpuset() with it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2013-04-07 09:29:50 -07:00
parent d9c10ddddc
commit 8cc9934520
3 changed files with 35 additions and 45 deletions
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1
include/linux/cgroup.h
View File

@ -696,6 +696,7 @@ int cgroup_scan_tasks(struct cgroup_scanner *scan);
int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
bool threadgroup);
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
/*
* CSS ID is ID for cgroup_subsys_state structs under subsys. This only works

28
kernel/cgroup.c
View File

@ -3269,6 +3269,34 @@ int cgroup_scan_tasks(struct cgroup_scanner *scan)
return 0;
}
static void cgroup_transfer_one_task(struct task_struct *task,
struct cgroup_scanner *scan)
{
struct cgroup *new_cgroup = scan->data;
cgroup_lock();
cgroup_attach_task(new_cgroup, task, false);
cgroup_unlock();
}
/**
* cgroup_trasnsfer_tasks - move tasks from one cgroup to another
* @to: cgroup to which the tasks will be moved
* @from: cgroup in which the tasks currently reside
*/
int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
{
struct cgroup_scanner scan;
scan.cg = from;
scan.test_task = NULL; /* select all tasks in cgroup */
scan.process_task = cgroup_transfer_one_task;
scan.heap = NULL;
scan.data = to;
return cgroup_scan_tasks(&scan);
}
/*
* Stuff for reading the 'tasks'/'procs' files.
*

51
kernel/cpuset.c
View File

@ -1994,50 +1994,6 @@ int __init cpuset_init(void)
return 0;
}
/**
* cpuset_do_move_task - move a given task to another cpuset
* @tsk: pointer to task_struct the task to move
* @scan: struct cgroup_scanner contained in its struct cpuset_hotplug_scanner
*
* Called by cgroup_scan_tasks() for each task in a cgroup.
* Return nonzero to stop the walk through the tasks.
*/
static void cpuset_do_move_task(struct task_struct *tsk,
struct cgroup_scanner *scan)
{
struct cgroup *new_cgroup = scan->data;
cgroup_lock();
cgroup_attach_task(new_cgroup, tsk, false);
cgroup_unlock();
}
/**
* move_member_tasks_to_cpuset - move tasks from one cpuset to another
* @from: cpuset in which the tasks currently reside
* @to: cpuset to which the tasks will be moved
*
* Called with cpuset_mutex held
* callback_mutex must not be held, as cpuset_attach() will take it.
*
* The cgroup_scan_tasks() function will scan all the tasks in a cgroup,
* calling callback functions for each.
*/
static void move_member_tasks_to_cpuset(struct cpuset *from, struct cpuset *to)
{
struct cgroup_scanner scan;
scan.cg = from->css.cgroup;
scan.test_task = NULL; /* select all tasks in cgroup */
scan.process_task = cpuset_do_move_task;
scan.heap = NULL;
scan.data = to->css.cgroup;
if (cgroup_scan_tasks(&scan))
printk(KERN_ERR "move_member_tasks_to_cpuset: "
"cgroup_scan_tasks failed\n");
}
/*
* If CPU and/or memory hotplug handlers, below, unplug any CPUs
* or memory nodes, we need to walk over the cpuset hierarchy,
@ -2058,7 +2014,12 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
nodes_empty(parent->mems_allowed))
parent = parent_cs(parent);
move_member_tasks_to_cpuset(cs, parent);
if (cgroup_transfer_tasks(parent->css.cgroup, cs->css.cgroup)) {
rcu_read_lock();
printk(KERN_ERR "cpuset: failed to transfer tasks out of empty cpuset %s\n",
cgroup_name(cs->css.cgroup));
rcu_read_unlock();
}
}
/**