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Commit afeb0f9f authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: relocate cgroup_enable_task_cg_lists() 



Move it above so that prototype isn't necessary.  Let's also move the
definition of use_task_css_set_links next to it.

This is purely cosmetic.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent 56fde9e0

kernel/cgroup.c

+48 −55
Original line number Diff line number Diff line
@@ -173,7 +173,6 @@ static int cgroup_destroy_locked(struct cgroup *cgrp); 
static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],

			      bool is_add);

static void cgroup_pidlist_destroy_all(struct cgroup *cgrp);

static void cgroup_enable_task_cg_lists(void);



/**

 * cgroup_css - obtain a cgroup's css for the specified subsystem
@@ -370,14 +369,6 @@ static unsigned long css_set_hash(struct cgroup_subsys_state *css[]) 
	return key;

}



/*

 * We don't maintain the lists running through each css_set to its task

 * until after the first call to css_task_iter_start().  This reduces the

 * fork()/exit() overhead for people who have cgroups compiled into their

 * kernel but not actually in use.

 */

static bool use_task_css_set_links __read_mostly;



static void __put_css_set(struct css_set *cset, int taskexit)

{

	struct cgrp_cset_link *link, *tmp_link;
@@ -1307,6 +1298,54 @@ static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data) 
	return ret;

}



/*

 * To reduce the fork() overhead for systems that are not actually using

 * their cgroups capability, we don't maintain the lists running through

 * each css_set to its tasks until we see the list actually used - in other

 * words after the first mount.

 */

static bool use_task_css_set_links __read_mostly;



static void cgroup_enable_task_cg_lists(void)

{

	struct task_struct *p, *g;



	write_lock(&css_set_lock);



	if (use_task_css_set_links)

		goto out_unlock;



	use_task_css_set_links = true;



	/*

	 * We need tasklist_lock because RCU is not safe against

	 * while_each_thread(). Besides, a forking task that has passed

	 * cgroup_post_fork() without seeing use_task_css_set_links = 1

	 * is not guaranteed to have its child immediately visible in the

	 * tasklist if we walk through it with RCU.

	 */

	read_lock(&tasklist_lock);

	do_each_thread(g, p) {

		task_lock(p);



		WARN_ON_ONCE(!list_empty(&p->cg_list) ||

			     task_css_set(p) != &init_css_set);



		/*

		 * We should check if the process is exiting, otherwise

		 * it will race with cgroup_exit() in that the list

		 * entry won't be deleted though the process has exited.

		 */

		if (!(p->flags & PF_EXITING))

			list_add(&p->cg_list, &task_css_set(p)->tasks);



		task_unlock(p);

	} while_each_thread(g, p);

	read_unlock(&tasklist_lock);

out_unlock:

	write_unlock(&css_set_lock);

}



static void init_cgroup_housekeeping(struct cgroup *cgrp)

{

	atomic_set(&cgrp->refcnt, 1);
@@ -2364,52 +2403,6 @@ int cgroup_task_count(const struct cgroup *cgrp) 
	return count;

}



/*

 * To reduce the fork() overhead for systems that are not actually using

 * their cgroups capability, we don't maintain the lists running through

 * each css_set to its tasks until we see the list actually used - in other

 * words after the first mount.

 */

static void cgroup_enable_task_cg_lists(void)

{

	struct task_struct *p, *g;



	write_lock(&css_set_lock);



	if (use_task_css_set_links)

		goto out_unlock;



	use_task_css_set_links = true;



	/*

	 * We need tasklist_lock because RCU is not safe against

	 * while_each_thread(). Besides, a forking task that has passed

	 * cgroup_post_fork() without seeing use_task_css_set_links = 1

	 * is not guaranteed to have its child immediately visible in the

	 * tasklist if we walk through it with RCU.

	 */

	read_lock(&tasklist_lock);

	do_each_thread(g, p) {

		task_lock(p);



		WARN_ON_ONCE(!list_empty(&p->cg_list) ||

			     task_css_set(p) != &init_css_set);



		/*

		 * We should check if the process is exiting, otherwise

		 * it will race with cgroup_exit() in that the list

		 * entry won't be deleted though the process has exited.

		 */

		if (!(p->flags & PF_EXITING))

			list_add(&p->cg_list, &task_css_set(p)->tasks);



		task_unlock(p);

	} while_each_thread(g, p);

	read_unlock(&tasklist_lock);

out_unlock:

	write_unlock(&css_set_lock);

}



/**

 * css_next_child - find the next child of a given css

 * @pos_css: the current position (%NULL to initiate traversal)