Use a better package name for utility functions.

osutils/fds.go

@@ -0,0 +1,18 @@
+// +build !windows,!darwin
+
+package osutils
+
+import (
+	"io/ioutil"
+	"path/filepath"
+	"strconv"
+)
+
+// GetOpenFds returns the number of open fds for the process provided by pid
+func GetOpenFds(pid int) (int, error) {
+	dirs, err := ioutil.ReadDir(filepath.Join("/proc", strconv.Itoa(pid), "fd"))
+	if err != nil {
+		return -1, err
+	}
+	return len(dirs), nil
+}

osutils/prctl.go

@@ -0,0 +1,43 @@
+// +build linux
+
+// http://man7.org/linux/man-pages/man2/prctl.2.html
+package osutils
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+// If arg2 is nonzero, set the "child subreaper" attribute of the
+// calling process; if arg2 is zero, unset the attribute.  When a
+// process is marked as a child subreaper, all of the children
+// that it creates, and their descendants, will be marked as
+// having a subreaper.  In effect, a subreaper fulfills the role
+// of init(1) for its descendant processes.  Upon termination of
+// a process that is orphaned (i.e., its immediate parent has
+// already terminated) and marked as having a subreaper, the
+// nearest still living ancestor subreaper will receive a SIGCHLD
+// signal and be able to wait(2) on the process to discover its
+// termination status.
+const PR_SET_CHILD_SUBREAPER = 36
+
+// Return the "child subreaper" setting of the caller, in the
+// location pointed to by (int *) arg2.
+const PR_GET_CHILD_SUBREAPER = 37
+
+// GetSubreaper returns the subreaper setting for the calling process
+func GetSubreaper() (int, error) {
+	var i uintptr
+	if _, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, PR_GET_CHILD_SUBREAPER, uintptr(unsafe.Pointer(&i)), 0); err != 0 {
+		return -1, err
+	}
+	return int(i), nil
+}
+
+// SetSubreaper sets the value i as the subreaper setting for the calling process
+func SetSubreaper(i int) error {
+	if _, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, PR_SET_CHILD_SUBREAPER, uintptr(i), 0); err != 0 {
+		return err
+	}
+	return nil
+}

osutils/reaper.go

@@ -0,0 +1,38 @@
+package osutils
+
+import (
+	"syscall"
+
+	"github.com/opencontainers/runc/libcontainer/utils"
+)
+
+// Exit is the wait4 information from an exited process
+type Exit struct {
+	Pid    int
+	Status int
+}
+
+// Reap reaps all child processes for the calling process and returns their
+// exit information
+func Reap() (exits []Exit, err error) {
+	var (
+		ws  syscall.WaitStatus
+		rus syscall.Rusage
+	)
+	for {
+		pid, err := syscall.Wait4(-1, &ws, syscall.WNOHANG, &rus)
+		if err != nil {
+			if err == syscall.ECHILD {
+				return exits, nil
+			}
+			return exits, err
+		}
+		if pid <= 0 {
+			return exits, nil
+		}
+		exits = append(exits, Exit{
+			Pid:    pid,
+			Status: utils.ExitStatus(ws),
+		})
+	}
+}