//go:build linux
// +build linux

/*
Copyright 2019 The Kubernetes Authors All rights reserved.

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 proc

import (
	"os"
	"os/signal"
	"syscall"

	"k8s.io/klog/v2"
)

// StartReaper starts a goroutine to reap processes if called from a process
// that has pid 1.
func StartReaper() {
	if os.Getpid() == 1 {
		klog.V(4).Infof("Launching reaper")
		go func() {
			sigs := make(chan os.Signal, 1)
			signal.Notify(sigs, syscall.SIGCHLD)
			for {
				// Wait for a child to terminate
				sig := <-sigs
				klog.V(4).Infof("Signal received: %v", sig)
				for {
					// Reap processes
					cpid, _ := syscall.Wait4(-1, nil, syscall.WNOHANG, nil)
					if cpid < 1 {
						break
					}

					klog.V(4).Infof("Reaped process with pid %d", cpid)
				}
			}
		}()
	}
}