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Commit 9db8de37 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: cosmetic updates to cgroup_attach_task() 



cgroup_attach_task() is planned to go through restructuring.  Let's
tidy it up a bit in preparation.

* Update cgroup_attach_task() to receive the target task argument in
  @leader instead of @tsk.

* Rename @tsk to @task.

* Rename @retval to @ret.

This is purely cosmetic.

v2: get_nr_threads() was using uninitialized @task instead of @leader.
    Fixed.  Reported by Dan Carpenter.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
parent bc668c75

kernel/cgroup.c

+23 −22
Original line number Diff line number Diff line
@@ -1728,20 +1728,20 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp, 
/**

 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup

 * @cgrp: the cgroup to attach to

 * @tsk: the task or the leader of the threadgroup to be attached

 * @leader: the task or the leader of the threadgroup to be attached

 * @threadgroup: attach the whole threadgroup?

 *

 * Call holding cgroup_mutex and the group_rwsem of the leader. Will take

 * task_lock of @tsk or each thread in the threadgroup individually in turn.

 */

static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,

static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *leader,

			      bool threadgroup)

{

	int retval, i, group_size;

	int ret, i, group_size;

	struct cgroupfs_root *root = cgrp->root;

	struct cgroup_subsys_state *css, *failed_css = NULL;

	/* threadgroup list cursor and array */

	struct task_struct *leader = tsk;

	struct task_struct *task;

	struct task_and_cgroup *tc;

	struct flex_array *group;

	struct cgroup_taskset tset = { };
@@ -1754,7 +1754,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk, 
	 * threads exit, this will just be an over-estimate.

	 */

	if (threadgroup)

		group_size = get_nr_threads(tsk);

		group_size = get_nr_threads(leader);

	else

		group_size = 1;

	/* flex_array supports very large thread-groups better than kmalloc. */
@@ -1762,8 +1762,8 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk, 
	if (!group)

		return -ENOMEM;

	/* pre-allocate to guarantee space while iterating in rcu read-side. */

	retval = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);

	if (retval)

	ret = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);

	if (ret)

		goto out_free_group_list;



	i = 0;
@@ -1774,17 +1774,18 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk, 
	 */

	down_read(&css_set_rwsem);

	rcu_read_lock();

	task = leader;

	do {

		struct task_and_cgroup ent;



		/* @tsk either already exited or can't exit until the end */

		if (tsk->flags & PF_EXITING)

		/* @task either already exited or can't exit until the end */

		if (task->flags & PF_EXITING)

			goto next;



		/* as per above, nr_threads may decrease, but not increase. */

		BUG_ON(i >= group_size);

		ent.task = tsk;

		ent.cgrp = task_cgroup_from_root(tsk, root);

		ent.task = task;

		ent.cgrp = task_cgroup_from_root(task, root);

		/* nothing to do if this task is already in the cgroup */

		if (ent.cgrp == cgrp)

			goto next;
@@ -1792,13 +1793,13 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk, 
		 * saying GFP_ATOMIC has no effect here because we did prealloc

		 * earlier, but it's good form to communicate our expectations.

		 */

		retval = flex_array_put(group, i, &ent, GFP_ATOMIC);

		BUG_ON(retval != 0);

		ret = flex_array_put(group, i, &ent, GFP_ATOMIC);

		BUG_ON(ret != 0);

		i++;

	next:

		if (!threadgroup)

			break;

	} while_each_thread(leader, tsk);

	} while_each_thread(leader, task);

	rcu_read_unlock();

	up_read(&css_set_rwsem);

	/* remember the number of threads in the array for later. */
@@ -1807,7 +1808,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk, 
	tset.tc_array_len = group_size;



	/* methods shouldn't be called if no task is actually migrating */

	retval = 0;

	ret = 0;

	if (!group_size)

		goto out_free_group_list;
@@ -1816,8 +1817,8 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk, 
	 */

	for_each_css(css, i, cgrp) {

		if (css->ss->can_attach) {

			retval = css->ss->can_attach(css, &tset);

			if (retval) {

			ret = css->ss->can_attach(css, &tset);

			if (ret) {

				failed_css = css;

				goto out_cancel_attach;

			}
@@ -1835,7 +1836,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk, 
		old_cset = task_css_set(tc->task);

		tc->cset = find_css_set(old_cset, cgrp);

		if (!tc->cset) {

			retval = -ENOMEM;

			ret = -ENOMEM;

			goto out_put_css_set_refs;

		}

	}
@@ -1863,9 +1864,9 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk, 
	/*

	 * step 5: success! and cleanup

	 */

	retval = 0;

	ret = 0;

out_put_css_set_refs:

	if (retval) {

	if (ret) {

		for (i = 0; i < group_size; i++) {

			tc = flex_array_get(group, i);

			if (!tc->cset)
@@ -1874,7 +1875,7 @@ out_put_css_set_refs: 
		}

	}

out_cancel_attach:

	if (retval) {

	if (ret) {

		for_each_css(css, i, cgrp) {

			if (css == failed_css)

				break;
@@ -1884,7 +1885,7 @@ out_cancel_attach: 
	}

out_free_group_list:

	flex_array_free(group);

	return retval;

	return ret;

}



/*