From 78f6519ed0766e36f08954810ce05f19212242a6 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Michal=20Koutn=C3=BD?= Date: Tue, 11 Mar 2025 13:36:26 +0100 Subject: [PATCH] cgroup: Add deprecation message to legacy freezer controller MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit As explained in the commit 76f969e8948d8 ("cgroup: cgroup v2 freezer"), the original freezer is imperfect, some users may unwittingly rely on it when there exists the alternative of v2. Print a message when it happens and explain that in the docs. Signed-off-by: Michal Koutný Signed-off-by: Tejun Heo --- Documentation/admin-guide/cgroup-v1/freezer-subsystem.rst | 4 ++++ kernel/cgroup/legacy_freezer.c | 6 ++++-- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/cgroup-v1/freezer-subsystem.rst b/Documentation/admin-guide/cgroup-v1/freezer-subsystem.rst index 582d3427de3f..a964aff373b1 100644 --- a/Documentation/admin-guide/cgroup-v1/freezer-subsystem.rst +++ b/Documentation/admin-guide/cgroup-v1/freezer-subsystem.rst @@ -125,3 +125,7 @@ to unfreeze all tasks in the container:: This is the basic mechanism which should do the right thing for user space task in a simple scenario. + +This freezer implementation is affected by shortcomings (see commit +76f969e8948d8 ("cgroup: cgroup v2 freezer")) and cgroup v2 freezer is +recommended. diff --git a/kernel/cgroup/legacy_freezer.c b/kernel/cgroup/legacy_freezer.c index 074653f964c1..039d1eb2f215 100644 --- a/kernel/cgroup/legacy_freezer.c +++ b/kernel/cgroup/legacy_freezer.c @@ -430,9 +430,11 @@ static ssize_t freezer_write(struct kernfs_open_file *of, if (strcmp(buf, freezer_state_strs(0)) == 0) freeze = false; - else if (strcmp(buf, freezer_state_strs(CGROUP_FROZEN)) == 0) + else if (strcmp(buf, freezer_state_strs(CGROUP_FROZEN)) == 0) { + pr_info_once("Freezing with imperfect legacy cgroup freezer. " + "See cgroup.freeze of cgroup v2\n"); freeze = true; - else + } else return -EINVAL; freezer_change_state(css_freezer(of_css(of)), freeze); -- 2.25.1