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From:   "haifeng.xu" <haifeng.xu@shopee.com>
To:     tj@kernel.org
Cc:     lizefan.x@bytedance.com, hannes@cmpxchg.org,
        cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
        "haifeng.xu" <haifeng.xu@shopee.com>
Subject: [PATCH] cgroup: Simplify code in css_set_move_task
Date:   Thu, 20 Oct 2022 07:47:01 +0000
Message-Id: <20221020074701.84326-1-haifeng.xu@shopee.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Check the populated state of css_set in css_set_update_populated
and update the populated state of to_cset after from_cset is updated.

Signed-off-by: haifeng.xu <haifeng.xu@shopee.com>
---
 kernel/cgroup/cgroup.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index d922773fa90b..6c474be57f91 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -861,7 +861,8 @@ static void css_set_update_populated(struct css_set *cset, bool populated)
 {
 	struct cgrp_cset_link *link;
 
-	lockdep_assert_held(&css_set_lock);
+	if (!cset || css_set_populated(cset))
+		return;
 
 	list_for_each_entry(link, &cset->cgrp_links, cgrp_link)
 		cgroup_update_populated(link->cgrp, populated);
@@ -903,16 +904,12 @@ static void css_set_move_task(struct task_struct *task,
 {
 	lockdep_assert_held(&css_set_lock);
 
-	if (to_cset && !css_set_populated(to_cset))
-		css_set_update_populated(to_cset, true);
-
 	if (from_cset) {
 		WARN_ON_ONCE(list_empty(&task->cg_list));
 
 		css_set_skip_task_iters(from_cset, task);
 		list_del_init(&task->cg_list);
-		if (!css_set_populated(from_cset))
-			css_set_update_populated(from_cset, false);
+		css_set_update_populated(from_cset, false);
 	} else {
 		WARN_ON_ONCE(!list_empty(&task->cg_list));
 	}
@@ -926,6 +923,7 @@ static void css_set_move_task(struct task_struct *task,
 		WARN_ON_ONCE(task->flags & PF_EXITING);
 
 		cgroup_move_task(task, to_cset);
+		css_set_update_populated(to_cset, true);
 		list_add_tail(&task->cg_list, use_mg_tasks ? &to_cset->mg_tasks :
 							     &to_cset->tasks);
 	}
-- 
2.25.1