move pkg/system: process to a separate package

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

daemon/container_operations_unix.go

@@ -15,8 +15,8 @@ import (
 	"github.com/docker/docker/errdefs"
 	"github.com/docker/docker/libnetwork"
 	"github.com/docker/docker/pkg/idtools"
+	"github.com/docker/docker/pkg/process"
 	"github.com/docker/docker/pkg/stringid"
-	"github.com/docker/docker/pkg/system"
 	"github.com/docker/docker/runconfig"
 	"github.com/moby/sys/mount"
 	"github.com/opencontainers/selinux/go-selinux/label"
@@ -352,9 +352,9 @@ func killProcessDirectly(container *container.Container) error {
 	}
 
 	// In case there were some exceptions(e.g., state of zombie and D)
-	if system.IsProcessAlive(pid) {
+	if process.Alive(pid) {
 		// Since we can not kill a zombie pid, add zombie check here
-		isZombie, err := system.IsProcessZombie(pid)
+		isZombie, err := process.Zombie(pid)
 		if err != nil {
 			logrus.WithError(err).WithField("container", container.ID).Warn("Container state is invalid")
 			return err

libcontainerd/supervisor/remote_daemon.go

@@ -14,6 +14,7 @@ import (
 	"github.com/containerd/containerd"
 	"github.com/containerd/containerd/services/server/config"
 	"github.com/containerd/containerd/sys"
+	"github.com/docker/docker/pkg/process"
 	"github.com/docker/docker/pkg/system"
 	"github.com/pelletier/go-toml"
 	"github.com/pkg/errors"
@@ -145,7 +146,7 @@ func (r *remote) getContainerdPid() (int, error) {
 		if err != nil {
 			return -1, err
 		}
-		if system.IsProcessAlive(int(pid)) {
+		if process.Alive(int(pid)) {
 			return int(pid), nil
 		}
 	}
@@ -238,7 +239,7 @@ func (r *remote) startContainerd() error {
 
 	err = os.WriteFile(r.pidFile, []byte(strconv.Itoa(r.daemonPid)), 0660)
 	if err != nil {
-		system.KillProcess(r.daemonPid)
+		process.Kill(r.daemonPid)
 		return errors.Wrap(err, "libcontainerd: failed to save daemon pid to disk")
 	}
 
@@ -357,7 +358,7 @@ func (r *remote) monitorDaemon(ctx context.Context) {
 			r.logger.WithError(err).WithField("binary", binaryName).Debug("daemon is not responding")
 
 			transientFailureCount++
-			if transientFailureCount < maxConnectionRetryCount || system.IsProcessAlive(r.daemonPid) {
+			if transientFailureCount < maxConnectionRetryCount || process.Alive(r.daemonPid) {
 				delay = time.Duration(transientFailureCount) * 200 * time.Millisecond
 				continue
 			}
@@ -365,7 +366,7 @@ func (r *remote) monitorDaemon(ctx context.Context) {
 			client = nil
 		}
 
-		if system.IsProcessAlive(r.daemonPid) {
+		if process.Alive(r.daemonPid) {
 			r.logger.WithField("pid", r.daemonPid).Info("killing and restarting containerd")
 			r.killDaemon()
 		}

libcontainerd/supervisor/remote_daemon_linux.go

@@ -7,7 +7,7 @@ import (
 	"time"
 
 	"github.com/containerd/containerd/defaults"
-	"github.com/docker/docker/pkg/system"
+	"github.com/docker/docker/pkg/process"
 )
 
 const (
@@ -35,13 +35,13 @@ func (r *remote) stopDaemon() {
 	syscall.Kill(r.daemonPid, syscall.SIGTERM)
 	// Wait up to 15secs for it to stop
 	for i := time.Duration(0); i < shutdownTimeout; i += time.Second {
-		if !system.IsProcessAlive(r.daemonPid) {
+		if !process.Alive(r.daemonPid) {
 			break
 		}
 		time.Sleep(time.Second)
 	}
 
-	if system.IsProcessAlive(r.daemonPid) {
+	if process.Alive(r.daemonPid) {
 		r.logger.WithField("pid", r.daemonPid).Warn("daemon didn't stop within 15 secs, killing it")
 		syscall.Kill(r.daemonPid, syscall.SIGKILL)
 	}
@@ -51,7 +51,7 @@ func (r *remote) killDaemon() {
 	// Try to get a stack trace
 	syscall.Kill(r.daemonPid, syscall.SIGUSR1)
 	<-time.After(100 * time.Millisecond)
-	system.KillProcess(r.daemonPid)
+	process.Kill(r.daemonPid)
 }
 
 func (r *remote) platformCleanup() {

libcontainerd/supervisor/remote_daemon_windows.go

@@ -3,7 +3,7 @@ package supervisor // import "github.com/docker/docker/libcontainerd/supervisor"
 import (
 	"os"
 
-	"github.com/docker/docker/pkg/system"
+	"github.com/docker/docker/pkg/process"
 )
 
 const (
@@ -40,7 +40,7 @@ func (r *remote) stopDaemon() {
 }
 
 func (r *remote) killDaemon() {
-	system.KillProcess(r.daemonPid)
+	process.Kill(r.daemonPid)
 }
 
 func (r *remote) platformCleanup() {

pkg/process/doc.go

@@ -0,0 +1,3 @@
+// Package process provides a set of basic functions to manage individual
+// processes.
+package process

pkg/system/process_unix.go → pkg/process/process_unix.go

@@ -1,7 +1,7 @@
 //go:build linux || freebsd || darwin
 // +build linux freebsd darwin
 
-package system // import "github.com/docker/docker/pkg/system"
+package process
 
 import (
 	"bytes"
@@ -11,8 +11,8 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-// IsProcessAlive returns true if process with a given pid is running.
-func IsProcessAlive(pid int) bool {
+// Alive returns true if process with a given pid is running.
+func Alive(pid int) bool {
 	err := unix.Kill(pid, 0)
 	if err == nil || err == unix.EPERM {
 		return true
@@ -21,14 +21,18 @@ func IsProcessAlive(pid int) bool {
 	return false
 }
 
-// KillProcess force-stops a process.
-func KillProcess(pid int) {
-	unix.Kill(pid, unix.SIGKILL)
+// Kill force-stops a process.
+func Kill(pid int) error {
+	err := unix.Kill(pid, unix.SIGKILL)
+	if err != nil && err != unix.ESRCH {
+		return err
+	}
+	return nil
 }
 
-// IsProcessZombie return true if process has a state with "Z"
+// Zombie return true if process has a state with "Z"
 // http://man7.org/linux/man-pages/man5/proc.5.html
-func IsProcessZombie(pid int) (bool, error) {
+func Zombie(pid int) (bool, error) {
 	data, err := os.ReadFile(fmt.Sprintf("/proc/%d/stat", pid))
 	if err != nil {
 		if os.IsNotExist(err) {

pkg/process/process_windows.go

@@ -0,0 +1,29 @@
+package process
+
+import "os"
+
+// Alive returns true if process with a given pid is running.
+func Alive(pid int) bool {
+	_, err := os.FindProcess(pid)
+
+	return err == nil
+}
+
+// Kill force-stops a process.
+func Kill(pid int) error {
+	p, err := os.FindProcess(pid)
+	if err == nil {
+		err = p.Kill()
+		if err != nil && err != os.ErrProcessDone {
+			return err
+		}
+	}
+	return nil
+}
+
+// Zombie is not supported on Windows.
+//
+// TODO(thaJeztah): remove once we remove the stubs from pkg/system.
+func Zombie(_ int) (bool, error) {
+	return false, nil
+}

pkg/system/process_deprecated.go

@@ -0,0 +1,27 @@
+//go:build linux || freebsd || darwin || windows
+// +build linux freebsd darwin windows
+
+package system
+
+import "github.com/docker/docker/pkg/process"
+
+var (
+	// IsProcessAlive returns true if process with a given pid is running.
+	//
+	// Deprecated: use [process.Alive].
+	IsProcessAlive = process.Alive
+
+	// IsProcessZombie return true if process has a state with "Z"
+	//
+	// Deprecated: use [process.Zombie].
+	//
+	// TODO(thaJeztah): remove the Windows implementation in process once we remove this stub.
+	IsProcessZombie = process.Zombie
+)
+
+// KillProcess force-stops a process.
+//
+// Deprecated: use [process.Kill].
+func KillProcess(pid int) {
+	_ = process.Kill(pid)
+}

pkg/system/process_windows.go

@@ -1,18 +0,0 @@
-package system // import "github.com/docker/docker/pkg/system"
-
-import "os"
-
-// IsProcessAlive returns true if process with a given pid is running.
-func IsProcessAlive(pid int) bool {
-	_, err := os.FindProcess(pid)
-
-	return err == nil
-}
-
-// KillProcess force-stops a process.
-func KillProcess(pid int) {
-	p, err := os.FindProcess(pid)
-	if err == nil {
-		_ = p.Kill()
-	}
-}