cgroup-util: introduce cg_is_threaded()

Signed-off-by: zhaoxiaohu <zhaoxiaohu@kuaishou.com>

backport-cgroup-util-introduce-cg_is_threaded.patch

@@ -0,0 +1,65 @@
+From 084e7706c25bf6cf0d6af4cc07fb1bb47e26b25e Mon Sep 17 00:00:00 2001
+From: Yu Watanabe <watanabe.yu+github@gmail.com>
+Date: Sun, 13 Feb 2022 20:39:04 +0900
+Subject: [PATCH] cgroup-util: introduce cg_is_threaded()
+
+Reference: https://github.com/systemd/systemd/pull/22498/commits/084e7706c25bf6cf0d6af4cc07fb1bb47e26b25e
+
+Signed-off-by: rpm-build <rpm-build>
+Signed-off-by: yuwang <yuwang@kuaishou.com>
+---
+ src/basic/cgroup-util.c | 24 ++++++++++++++++++++++++
+ src/basic/cgroup-util.h |  2 ++
+ 2 files changed, 26 insertions(+)
+
+diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
+index 79089ac..130536c 100644
+--- a/src/basic/cgroup-util.c
++++ b/src/basic/cgroup-util.c
+@@ -1642,6 +1642,30 @@ int cg_slice_to_path(const char *unit, char **ret) {
+         return 0;
+ }
+ 
++int cg_is_threaded(const char *controller, const char *path) {
++        _cleanup_free_ char *fs = NULL, *contents = NULL;
++        _cleanup_strv_free_ char **v = NULL;
++        int r;
++
++        r = cg_get_path(controller, path, "cgroup.type", &fs);
++        if (r < 0)
++                return r;
++
++        r = read_full_virtual_file(fs, &contents, NULL);
++        if (r == -ENOENT)
++                return false; /* Assume no. */
++        if (r < 0)
++                return r;
++
++        v = strv_split(contents, NULL);
++        if (!v)
++                return -ENOMEM;
++
++        /* If the cgroup is in the threaded mode, it contains "threaded".
++         * If one of the parents or siblings is in the threaded mode, it may contain "invalid". */
++        return strv_contains(v, "threaded") || strv_contains(v, "invalid");
++}
++
+ int cg_set_attribute(const char *controller, const char *path, const char *attribute, const char *value) {
+         _cleanup_free_ char *p = NULL;
+         int r;
+diff --git a/src/basic/cgroup-util.h b/src/basic/cgroup-util.h
+index faa253b..baeb8c4 100644
+--- a/src/basic/cgroup-util.h
++++ b/src/basic/cgroup-util.h
+@@ -188,6 +188,8 @@ int cg_pid_get_path(const char *controller, pid_t pid, char **path);
+ 
+ int cg_rmdir(const char *controller, const char *path);
+ 
++int cg_is_threaded(const char *controller, const char *path);
++
+ typedef enum  {
+         CG_KEY_MODE_GRACEFUL = 1 << 0,
+ } CGroupKeyMode;
+-- 
+2.33.0
+