internal: cgroups: support Tasks interface

Support obtaining pid list

Signed-off-by: Tonghao Zhang <tonghao@bamaicloud.com>

internal/cgroups/cgroups.go

@@ -54,6 +54,8 @@ type Cgroup interface {
 	UpdateRuntime(spec *specs.LinuxResources) error
 	// Add pids to cgroup.procs
 	AddProc(pid uint64) error
+	// Pids return pids of cgroups
+	Pids(path string) ([]int32, error)
 	// CpuUsage return cgroups user/system and total usage.
 	CpuUsage(path string) (*stats.CpuUsage, error)
 	// CpuStatRaw return cpu.stat raw data

internal/cgroups/pids/pids.go

@@ -0,0 +1,52 @@
+// Copyright 2025 The HuaTuo Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package pids
+
+import (
+	"bufio"
+	"os"
+	"path/filepath"
+	"strconv"
+)
+
+// 1. /sys/fs/cgroup/$GROUPPATH/cgroup.procs
+// 2. /sys/fs/cgroup/$GROUPPATH/cgroup.threads
+func Tasks(path, file string) ([]int32, error) {
+	f, err := os.Open(filepath.Join(path, file))
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	var (
+		out []int32
+		s   = bufio.NewScanner(f)
+	)
+
+	for s.Scan() {
+		if t := s.Text(); t != "" {
+			pid, err := strconv.ParseInt(t, 10, 0)
+			if err != nil {
+				return nil, err
+			}
+			out = append(out, int32(pid))
+		}
+	}
+
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
+	return out, nil
+}

internal/cgroups/v1/cgroups.go

@@ -18,6 +18,7 @@ import (
 	"math"
 
 	"huatuo-bamai/internal/cgroups/paths"
+	"huatuo-bamai/internal/cgroups/pids"
 	"huatuo-bamai/internal/cgroups/stats"
 	"huatuo-bamai/internal/utils/parseutil"
 
@@ -92,6 +93,10 @@ func (c *CgroupV1) AddProc(pid uint64) error {
 	return c.cgroup.AddProc(pid)
 }
 
+func (c *CgroupV1) Pids(path string) ([]int32, error) {
+	return pids.Tasks(paths.Path(subsysCpu, path), "tasks")
+}
+
 func (c *CgroupV1) CpuUsage(path string) (*stats.CpuUsage, error) {
 	statPath := paths.Path(subsysCpu, path, "cpuacct.stat")
 	raw, err := parseutil.RawKV(statPath)

internal/cgroups/v2/cgroups.go

@@ -20,6 +20,7 @@ import (
 	"strconv"
 
 	"huatuo-bamai/internal/cgroups/paths"
+	"huatuo-bamai/internal/cgroups/pids"
 	"huatuo-bamai/internal/cgroups/stats"
 	"huatuo-bamai/internal/utils/parseutil"
 
@@ -83,6 +84,10 @@ func (c *CgroupV2) AddProc(pid uint64) error {
 	return c.cgroup.AddProc(pid)
 }
 
+func (c *CgroupV2) Pids(path string) ([]int32, error) {
+	return pids.Tasks(paths.Path(path), "cgroup.threads")
+}
+
 func (c *CgroupV2) CpuStatRaw(path string) (map[string]uint64, error) {
 	return parseutil.RawKV(paths.Path(path, "cpu.stat"))
 }