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Tue, 11 Mar 2025 05:37:04 -0700 (PDT) From: =?UTF-8?q?Michal=20Koutn=C3=BD?= To: cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Cc: =?UTF-8?q?Michal=20Koutn=C3=BD?= , Tejun Heo , Johannes Weiner , Jonathan Corbet Subject: [PATCH v2 09/11] cgroup: Add deprecation message to legacy freezer controller Date: Tue, 11 Mar 2025 13:36:26 +0100 Message-ID: <20250311123640.530377-10-mkoutny@suse.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250311123640.530377-1-mkoutny@suse.com> References: <20250311123640.530377-1-mkoutny@suse.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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 --- 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 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); -- 2.48.1