From: Michal Koutný Date: Tue, 11 Mar 2025 12:36:26 +0000 (+0100) Subject: cgroup: Add deprecation message to legacy freezer controller X-Git-Tag: v6.15-rc1~228^2~5 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=78f6519ed0766e36f08954810ce05f19212242a6;p=thirdparty%2Fkernel%2Flinux.git cgroup: Add deprecation message to legacy freezer controller 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 --- diff --git a/Documentation/admin-guide/cgroup-v1/freezer-subsystem.rst b/Documentation/admin-guide/cgroup-v1/freezer-subsystem.rst index 582d3427de3f8..a964aff373b19 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 074653f964c1d..039d1eb2f215b 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);