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Commit 8cc99345 authored by Tejun Heo's avatar Tejun Heo
Browse files

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



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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent d9c10ddd

include/linux/cgroup.h

+1 −0
Original line number Diff line number Diff line
@@ -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

kernel/cgroup.c

+28 −0
Original line number Diff line number Diff line
@@ -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.

 *

kernel/cpuset.c

+6 −45
Original line number Diff line number Diff line
@@ -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();

	}

}



/**