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cgroup: pair max limit READ_ONCE() with WRITE_ONCE()

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cgroup.max.descendants and cgroup.max.depth are shown through seq_file.
Their show callbacks read cgrp->max_descendants and cgrp->max_depth with
READ_ONCE(), respectively.

The corresponding write callbacks update the same scalar fields while
holding the cgroup lock, but the seq_file show path does not serialize
against those stores. This leaves the lockless show-side loads annotated
with READ_ONCE(), while the corresponding stores remain plain stores.

Use WRITE_ONCE() for the updates so the intended lockless access is marked
consistently on both sides. This does not change locking, ordering, or
user-visible semantics.

Assisted-by: OpenAI-Codex:gpt-5.5
Signed-off-by: Ren Tamura <ren.tamura.oss@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Ren Tamura 2026-05-28 13:28:39 +09:00 committed by Tejun Heo
parent 98f0adb228
commit 336f87d742
1 changed files with 2 additions and 2 deletions
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4
kernel/cgroup/cgroup.c
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@ -3734,7 +3734,7 @@ static ssize_t cgroup_max_descendants_write(struct kernfs_open_file *of,
if (!cgrp)
return -ENOENT;
cgrp->max_descendants = descendants;
WRITE_ONCE(cgrp->max_descendants, descendants);
cgroup_kn_unlock(of->kn);
@ -3777,7 +3777,7 @@ static ssize_t cgroup_max_depth_write(struct kernfs_open_file *of,
if (!cgrp)
return -ENOENT;
cgrp->max_depth = depth;
WRITE_ONCE(cgrp->max_depth, depth);
cgroup_kn_unlock(of->kn);