Commit c59cd3d8 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: make cgroup_task_iter remember the cgroup being iterated 



Currently all cgroup_task_iter functions require @cgrp to be passed
in, which is superflous and increases chance of usage error.  Make
cgroup_task_iter remember the cgroup being iterated and drop @cgrp
argument from next and end functions.

This patch doesn't introduce any behavior differences.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
parent 0942eeee

include/linux/cgroup.h

+3 −3
Original line number Diff line number Diff line
@@ -891,14 +891,14 @@ css_next_descendant_post(struct cgroup_subsys_state *pos, 


/* A cgroup_task_iter should be treated as an opaque object */

struct cgroup_task_iter {

	struct cgroup			*origin_cgrp;

	struct list_head		*cset_link;

	struct list_head		*task;

};



void cgroup_task_iter_start(struct cgroup *cgrp, struct cgroup_task_iter *it);

struct task_struct *cgroup_task_iter_next(struct cgroup *cgrp,

					  struct cgroup_task_iter *it);

void cgroup_task_iter_end(struct cgroup *cgrp, struct cgroup_task_iter *it);

struct task_struct *cgroup_task_iter_next(struct cgroup_task_iter *it);

void cgroup_task_iter_end(struct cgroup_task_iter *it);

int cgroup_scan_tasks(struct cgroup_scanner *scan);

int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);

int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);

kernel/cgroup.c

+15 −17
Original line number Diff line number Diff line
@@ -3205,13 +3205,11 @@ EXPORT_SYMBOL_GPL(css_next_descendant_post); 


/**

 * cgroup_advance_task_iter - advance a task itererator to the next css_set

 * @cgrp: the cgroup to walk tasks of

 * @it: the iterator to advance

 *

 * Advance @it to the next css_set to walk.

 */

static void cgroup_advance_task_iter(struct cgroup *cgrp,

				     struct cgroup_task_iter *it)

static void cgroup_advance_task_iter(struct cgroup_task_iter *it)

{

	struct list_head *l = it->cset_link;

	struct cgrp_cset_link *link;
@@ -3220,7 +3218,7 @@ static void cgroup_advance_task_iter(struct cgroup *cgrp, 
	/* Advance to the next non-empty css_set */

	do {

		l = l->next;

		if (l == &cgrp->cset_links) {

		if (l == &it->origin_cgrp->cset_links) {

			it->cset_link = NULL;

			return;

		}
@@ -3257,21 +3255,22 @@ void cgroup_task_iter_start(struct cgroup *cgrp, struct cgroup_task_iter *it) 
		cgroup_enable_task_cg_lists();



	read_lock(&css_set_lock);



	it->origin_cgrp = cgrp;

	it->cset_link = &cgrp->cset_links;

	cgroup_advance_task_iter(cgrp, it);



	cgroup_advance_task_iter(it);

}



/**

 * cgroup_task_iter_next - return the next task for the iterator

 * @cgrp: the cgroup to walk tasks of

 * @it: the task iterator being iterated

 *

 * The "next" function for task iteration.  @it should have been

 * initialized via cgroup_task_iter_start().  Returns NULL when the

 * iteration reaches the end.

 */

struct task_struct *cgroup_task_iter_next(struct cgroup *cgrp,

					  struct cgroup_task_iter *it)

struct task_struct *cgroup_task_iter_next(struct cgroup_task_iter *it)

{

	struct task_struct *res;

	struct list_head *l = it->task;
@@ -3289,7 +3288,7 @@ struct task_struct *cgroup_task_iter_next(struct cgroup *cgrp, 
		 * We reached the end of this task list - move on to the

		 * next cgrp_cset_link.

		 */

		cgroup_advance_task_iter(cgrp, it);

		cgroup_advance_task_iter(it);

	} else {

		it->task = l;

	}
@@ -3298,12 +3297,11 @@ struct task_struct *cgroup_task_iter_next(struct cgroup *cgrp, 


/**

 * cgroup_task_iter_end - finish task iteration

 * @cgrp: the cgroup to walk tasks of

 * @it: the task iterator to finish

 *

 * Finish task iteration started by cgroup_task_iter_start().

 */

void cgroup_task_iter_end(struct cgroup *cgrp, struct cgroup_task_iter *it)

void cgroup_task_iter_end(struct cgroup_task_iter *it)

	__releases(css_set_lock)

{

	read_unlock(&css_set_lock);
@@ -3409,7 +3407,7 @@ int cgroup_scan_tasks(struct cgroup_scanner *scan) 
	 */

	heap->size = 0;

	cgroup_task_iter_start(scan->cgrp, &it);

	while ((p = cgroup_task_iter_next(scan->cgrp, &it))) {

	while ((p = cgroup_task_iter_next(&it))) {

		/*

		 * Only affect tasks that qualify per the caller's callback,

		 * if he provided one
@@ -3442,7 +3440,7 @@ int cgroup_scan_tasks(struct cgroup_scanner *scan) 
		 * the heap and wasn't inserted

		 */

	}

	cgroup_task_iter_end(scan->cgrp, &it);

	cgroup_task_iter_end(&it);



	if (heap->size) {

		for (i = 0; i < heap->size; i++) {
@@ -3664,7 +3662,7 @@ static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type, 
		return -ENOMEM;

	/* now, populate the array */

	cgroup_task_iter_start(cgrp, &it);

	while ((tsk = cgroup_task_iter_next(cgrp, &it))) {

	while ((tsk = cgroup_task_iter_next(&it))) {

		if (unlikely(n == length))

			break;

		/* get tgid or pid for procs or tasks file respectively */
@@ -3675,7 +3673,7 @@ static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type, 
		if (pid > 0) /* make sure to only use valid results */

			array[n++] = pid;

	}

	cgroup_task_iter_end(cgrp, &it);

	cgroup_task_iter_end(&it);

	length = n;

	/* now sort & (if procs) strip out duplicates */

	sort(array, length, sizeof(pid_t), cmppid, NULL);
@@ -3724,7 +3722,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) 
	cgrp = dentry->d_fsdata;



	cgroup_task_iter_start(cgrp, &it);

	while ((tsk = cgroup_task_iter_next(cgrp, &it))) {

	while ((tsk = cgroup_task_iter_next(&it))) {

		switch (tsk->state) {

		case TASK_RUNNING:

			stats->nr_running++;
@@ -3744,7 +3742,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) 
			break;

		}

	}

	cgroup_task_iter_end(cgrp, &it);

	cgroup_task_iter_end(&it);



err:

	return ret;

kernel/cgroup_freezer.c

+6 −6
Original line number Diff line number Diff line
@@ -281,7 +281,7 @@ static void update_if_frozen(struct cgroup_subsys_state *css) 
	/* are all tasks frozen? */

	cgroup_task_iter_start(css->cgroup, &it);



	while ((task = cgroup_task_iter_next(css->cgroup, &it))) {

	while ((task = cgroup_task_iter_next(&it))) {

		if (freezing(task)) {

			/*

			 * freezer_should_skip() indicates that the task
@@ -296,7 +296,7 @@ static void update_if_frozen(struct cgroup_subsys_state *css) 


	freezer->state |= CGROUP_FROZEN;

out_iter_end:

	cgroup_task_iter_end(css->cgroup, &it);

	cgroup_task_iter_end(&it);

out_unlock:

	spin_unlock_irq(&freezer->lock);

}
@@ -327,9 +327,9 @@ static void freeze_cgroup(struct freezer *freezer) 
	struct task_struct *task;



	cgroup_task_iter_start(cgroup, &it);

	while ((task = cgroup_task_iter_next(cgroup, &it)))

	while ((task = cgroup_task_iter_next(&it)))

		freeze_task(task);

	cgroup_task_iter_end(cgroup, &it);

	cgroup_task_iter_end(&it);

}



static void unfreeze_cgroup(struct freezer *freezer)
@@ -339,9 +339,9 @@ static void unfreeze_cgroup(struct freezer *freezer) 
	struct task_struct *task;



	cgroup_task_iter_start(cgroup, &it);

	while ((task = cgroup_task_iter_next(cgroup, &it)))

	while ((task = cgroup_task_iter_next(&it)))

		__thaw_task(task);

	cgroup_task_iter_end(cgroup, &it);

	cgroup_task_iter_end(&it);

}



/**

mm/memcontrol.c

+3 −3
Original line number Diff line number Diff line
@@ -1804,7 +1804,7 @@ static void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask, 
		struct task_struct *task;



		cgroup_task_iter_start(cgroup, &it);

		while ((task = cgroup_task_iter_next(cgroup, &it))) {

		while ((task = cgroup_task_iter_next(&it))) {

			switch (oom_scan_process_thread(task, totalpages, NULL,

							false)) {

			case OOM_SCAN_SELECT:
@@ -1817,7 +1817,7 @@ static void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask, 
			case OOM_SCAN_CONTINUE:

				continue;

			case OOM_SCAN_ABORT:

				cgroup_task_iter_end(cgroup, &it);

				cgroup_task_iter_end(&it);

				mem_cgroup_iter_break(memcg, iter);

				if (chosen)

					put_task_struct(chosen);
@@ -1834,7 +1834,7 @@ static void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask, 
				get_task_struct(chosen);

			}

		}

		cgroup_task_iter_end(cgroup, &it);

		cgroup_task_iter_end(&it);

	}



	if (!chosen)

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