system: always move pause process when running on systemd

when running on a systemd with systemd, always try to move the pause
process to its own scope.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
(cherry picked from commit 9c1e27fdd536f6026efe3da4360755a3e9135ca8)

2 files changed, 19 insertions, 11 deletions

diff --git a/pkg/domain/infra/abi/system.go b/pkg/domain/infra/abi/system.go
index 0f7492354..7140618bb 100644
--- a/pkg/domain/infra/abi/system.go
+++ b/pkg/domain/infra/abi/system.go
@@ -9,7 +9,6 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strconv"
-	"strings"
 
 	"github.com/containers/common/pkg/config"
 	"github.com/containers/podman/v3/libpod/define"
@@ -71,11 +70,7 @@ func (ic *ContainerEngine) SetupRootless(_ context.Context, noMoveProcess bool)
 			if err != nil {
 				return err
 			}
-
-			initCommand, err := ioutil.ReadFile("/proc/1/comm")
-			// On errors, default to systemd
-			runsUnderSystemd := err != nil || strings.TrimRight(string(initCommand), "\n") == "systemd"
-
+			runsUnderSystemd := utils.RunsOnSystemd()
 			unitName := fmt.Sprintf("podman-%d.scope", os.Getpid())
 			if runsUnderSystemd || conf.Engine.CgroupManager == config.SystemdCgroupsManager {
 				if err := utils.RunUnderSystemdScope(os.Getpid(), "user.slice", unitName); err != nil {
@@ -121,11 +116,7 @@ func (ic *ContainerEngine) SetupRootless(_ context.Context, noMoveProcess bool)
 	became, ret, err = rootless.TryJoinFromFilePaths(pausePidPath, true, paths)
 
 	if err := movePauseProcessToScope(pausePidPath); err != nil {
-		conf, err2 := ic.Config(context.Background())
-		if err2 != nil {
-			return err
-		}
-		if conf.Engine.CgroupManager == config.SystemdCgroupsManager {
+		if utils.RunsOnSystemd() {
 			logrus.Warnf("Failed to add pause process to systemd sandbox cgroup: %v", err)
 		} else {
 			logrus.Debugf("Failed to add pause process to systemd sandbox cgroup: %v", err)
diff --git a/utils/utils.go b/utils/utils.go
index 2e415130e..e2760d225 100644
--- a/utils/utils.go
+++ b/utils/utils.go
@@ -4,10 +4,12 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os"
 	"os/exec"
 	"strconv"
 	"strings"
+	"sync"
 
 	"github.com/containers/podman/v3/libpod/define"
 	"github.com/containers/storage/pkg/archive"
@@ -155,3 +157,18 @@ func RemoveScientificNotationFromFloat(x float64) (float64, error) {
 	}
 	return result, nil
 }
+
+var (
+	runsOnSystemdOnce sync.Once
+	runsOnSystemd     bool
+)
+
+// RunsOnSystemd returns whether the system is using systemd
+func RunsOnSystemd() bool {
+	runsOnSystemdOnce.Do(func() {
+		initCommand, err := ioutil.ReadFile("/proc/1/comm")
+		// On errors, default to systemd
+		runsOnSystemd = err != nil || strings.TrimRight(string(initCommand), "\n") == "systemd"
+	})
+	return runsOnSystemd
+}