From: "Michal Koutný" <mkoutny@suse.com>
To: cgroups@vger.kernel.org
Cc: alex.shi@linux.alibaba.com, guro@fb.com, hannes@cmpxchg.org,
kernel-team@android.com, linger.lee@mediatek.com,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-mediatek@lists.infradead.org, lizefan@huawei.com,
matthias.bgg@gmail.com, shuah@kernel.org, surenb@google.com,
tj@kernel.org, tomcherry@google.com
Subject: [PATCH v2 2/3] cgroup: Clean up css_set task traversal
Date: Fri, 24 Jan 2020 12:40:16 +0100 [thread overview]
Message-ID: <20200124114017.8363-3-mkoutny@suse.com> (raw)
In-Reply-To: <20200124114017.8363-1-mkoutny@suse.com>
css_task_iter stores pointer to head of each iterable list, this dates
back to commit 0f0a2b4fa621 ("cgroup: reorganize css_task_iter") when we
did not store cur_cset. Let us utilize list heads directly in cur_cset
and streamline css_task_iter_advance_css_set a bit. This is no
intentional function change.
Signed-off-by: Michal Koutný <mkoutny@suse.com>
---
include/linux/cgroup.h | 3 ---
kernel/cgroup/cgroup.c | 61 +++++++++++++++++++-----------------------
2 files changed, 28 insertions(+), 36 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index e75d2191226b..f1219b927817 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -58,9 +58,6 @@ struct css_task_iter {
struct list_head *tcset_head;
struct list_head *task_pos;
- struct list_head *tasks_head;
- struct list_head *mg_tasks_head;
- struct list_head *dying_tasks_head;
struct list_head *cur_tasks_head;
struct css_set *cur_cset;
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index a6e3619e013b..14e0e360a2b4 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4395,29 +4395,24 @@ static void css_task_iter_advance_css_set(struct css_task_iter *it)
lockdep_assert_held(&css_set_lock);
- /* Advance to the next non-empty css_set */
- do {
- cset = css_task_iter_next_css_set(it);
- if (!cset) {
- it->task_pos = NULL;
- return;
+ /* Advance to the next non-empty css_set and find first non-empty tasks list*/
+ while ((cset = css_task_iter_next_css_set(it))) {
+ if (!list_empty(&cset->tasks)) {
+ it->cur_tasks_head = &cset->tasks;
+ break;
+ } else if (!list_empty(&cset->mg_tasks)) {
+ it->cur_tasks_head = &cset->mg_tasks;
+ break;
+ } else if (!list_empty(&cset->dying_tasks)) {
+ it->cur_tasks_head = &cset->dying_tasks;
+ break;
}
- } while (!css_set_populated(cset) && list_empty(&cset->dying_tasks));
-
- if (!list_empty(&cset->tasks)) {
- it->task_pos = cset->tasks.next;
- it->cur_tasks_head = &cset->tasks;
- } else if (!list_empty(&cset->mg_tasks)) {
- it->task_pos = cset->mg_tasks.next;
- it->cur_tasks_head = &cset->mg_tasks;
- } else {
- it->task_pos = cset->dying_tasks.next;
- it->cur_tasks_head = &cset->dying_tasks;
}
-
- it->tasks_head = &cset->tasks;
- it->mg_tasks_head = &cset->mg_tasks;
- it->dying_tasks_head = &cset->dying_tasks;
+ if (!cset) {
+ it->task_pos = NULL;
+ return;
+ }
+ it->task_pos = it->cur_tasks_head->next;
/*
* We don't keep css_sets locked across iteration steps and thus
@@ -4462,24 +4457,24 @@ static void css_task_iter_advance(struct css_task_iter *it)
repeat:
if (it->task_pos) {
/*
- * Advance iterator to find next entry. cset->tasks is
- * consumed first and then ->mg_tasks. After ->mg_tasks,
- * we move onto the next cset.
+ * Advance iterator to find next entry. We go through cset
+ * tasks, mg_tasks and dying_tasks, when consumed we move onto
+ * the next cset.
*/
if (it->flags & CSS_TASK_ITER_SKIPPED)
it->flags &= ~CSS_TASK_ITER_SKIPPED;
else
it->task_pos = it->task_pos->next;
- if (it->task_pos == it->tasks_head) {
- it->task_pos = it->mg_tasks_head->next;
- it->cur_tasks_head = it->mg_tasks_head;
+ if (it->task_pos == &it->cur_cset->tasks) {
+ it->cur_tasks_head = &it->cur_cset->mg_tasks;
+ it->task_pos = it->cur_tasks_head->next;
}
- if (it->task_pos == it->mg_tasks_head) {
- it->task_pos = it->dying_tasks_head->next;
- it->cur_tasks_head = it->dying_tasks_head;
+ if (it->task_pos == &it->cur_cset->mg_tasks) {
+ it->cur_tasks_head = &it->cur_cset->dying_tasks;
+ it->task_pos = it->cur_tasks_head->next;
}
- if (it->task_pos == it->dying_tasks_head)
+ if (it->task_pos == &it->cur_cset->dying_tasks)
css_task_iter_advance_css_set(it);
} else {
/* called from start, proceed to the first cset */
@@ -4497,12 +4492,12 @@ static void css_task_iter_advance(struct css_task_iter *it)
goto repeat;
/* and dying leaders w/o live member threads */
- if (it->cur_tasks_head == it->dying_tasks_head &&
+ if (it->cur_tasks_head == &it->cur_cset->dying_tasks &&
!atomic_read(&task->signal->live))
goto repeat;
} else {
/* skip all dying ones */
- if (it->cur_tasks_head == it->dying_tasks_head)
+ if (it->cur_tasks_head == &it->cur_cset->dying_tasks)
goto repeat;
}
}
--
2.24.1
next prev parent reply other threads:[~2020-01-24 11:40 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 4:36 [PATCH 1/2] cgroup: allow deletion of cgroups containing only dying processes Suren Baghdasaryan
2020-01-16 4:36 ` [PATCH 2/2] kselftest/cgroup: add cgroup destruction test Suren Baghdasaryan
2020-01-17 15:15 ` [PATCH 0/3] cgroup: Iterate tasks that did not finish do_exit() Michal Koutný
2020-01-17 15:15 ` [PATCH 1/3] cgroup: Unify css_set task lists Michal Koutný
2020-01-17 16:59 ` Tejun Heo
2020-01-17 15:15 ` [PATCH 2/3] cgroup: Iterate tasks that did not finish do_exit() Michal Koutný
2020-01-17 17:28 ` Tejun Heo
2020-01-17 18:41 ` Suren Baghdasaryan
2020-01-20 14:56 ` Michal Koutný
2020-01-24 11:40 ` [PATCH v2 0/3] " Michal Koutný
2020-01-24 11:40 ` [PATCH v2 1/3] " Michal Koutný
2020-01-24 22:56 ` Suren Baghdasaryan
2020-02-05 17:27 ` Suren Baghdasaryan
2020-02-12 22:03 ` Tejun Heo
2020-01-24 11:40 ` Michal Koutný [this message]
2020-01-24 11:40 ` [PATCH v2 3/3] kselftest/cgroup: add cgroup destruction test Michal Koutný
2020-02-12 22:10 ` Tejun Heo
2020-01-17 15:15 ` [PATCH " Michal Koutný
2020-01-17 17:30 ` [PATCH 0/3] cgroup: Iterate tasks that did not finish do_exit() Suren Baghdasaryan
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