rootless: automatically recreate the pause.pid file

if the pause process cannot be joined, remove the pause.pid while
keeping a lock on it, and try to recreate it.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/pkg/rootless/rootless.go b/pkg/rootless/rootless.go
new file mode 100644
index 000000000..7e9fe9db6
--- /dev/null
+++ b/pkg/rootless/rootless.go
@@ -0,0 +1,45 @@
+package rootless
+
+import (
+	"os"
+
+	"github.com/containers/storage"
+	"github.com/pkg/errors"
+)
+
+func TryJoinPauseProcess(pausePidPath string) (bool, int, error) {
+	if _, err := os.Stat(pausePidPath); err != nil {
+		return false, -1, nil
+	}
+
+	became, ret, err := TryJoinFromFilePaths("", false, []string{pausePidPath})
+	if err == nil {
+		return became, ret, err
+	}
+
+	// It could not join the pause process, let's lock the file before trying to delete it.
+	pidFileLock, err := storage.GetLockfile(pausePidPath)
+	if err != nil {
+		// The file was deleted by another process.
+		if os.IsNotExist(err) {
+			return false, -1, nil
+		}
+		return false, -1, errors.Wrapf(err, "error acquiring lock on %s", pausePidPath)
+	}
+
+	pidFileLock.Lock()
+	defer func() {
+		if pidFileLock.Locked() {
+			pidFileLock.Unlock()
+		}
+	}()
+
+	// Now the pause PID file is locked.  Try to join once again in case it changed while it was not locked.
+	became, ret, err = TryJoinFromFilePaths("", false, []string{pausePidPath})
+	if err != nil {
+		// It is still failing.  We can safely remove it.
+		os.Remove(pausePidPath)
+		return false, -1, nil
+	}
+	return became, ret, err
+}