import (
"bytes"
- "io/ioutil"
- "log"
+ "fmt"
+ "io/fs"
)
// Return the current process's cgroup for the given subsystem.
-func findCgroup(subsystem string) string {
+//
+// If the host has cgroups v2 and not v1 (i.e., unified mode), return
+// the current process's cgroup.
+func findCgroup(fsys fs.FS, subsystem string) (string, error) {
subsys := []byte(subsystem)
- cgroups, err := ioutil.ReadFile("/proc/self/cgroup")
+ cgroups, err := fs.ReadFile(fsys, "proc/self/cgroup")
if err != nil {
- log.Fatal(err)
+ return "", err
}
for _, line := range bytes.Split(cgroups, []byte("\n")) {
toks := bytes.SplitN(line, []byte(":"), 4)
if len(toks) < 3 {
continue
}
+ if len(toks[1]) == 0 && string(toks[0]) == "0" {
+ // cgroups v2: "0::$PATH"
+ //
+ // In "hybrid" mode, this entry is last, so we
+ // use it when the specified subsystem doesn't
+ // match a cgroups v1 entry.
+ //
+ // In "unified" mode, this is the only entry,
+ // so we use it regardless of which subsystem
+ // was specified.
+ return string(toks[2]), nil
+ }
for _, s := range bytes.Split(toks[1], []byte(",")) {
+ // cgroups v1: "7:cpu,cpuacct:/user.slice"
if bytes.Compare(s, subsys) == 0 {
- return string(toks[2])
+ return string(toks[2]), nil
}
}
}
- log.Fatalf("subsystem %q not found in /proc/self/cgroup", subsystem)
- return ""
+ return "", fmt.Errorf("subsystem %q not found in /proc/self/cgroup", subsystem)
}