Add prctl to utils package

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

containerd/reap_linux.go

@@ -9,24 +9,10 @@ import (
 
 	"github.com/Sirupsen/logrus"
 	"github.com/docker/containerd"
+	"github.com/docker/containerd/util"
 	"github.com/opencontainers/runc/libcontainer/utils"
 )
 
-// http://man7.org/linux/man-pages/man2/prctl.2.html
-//
-// 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
-
 func startSignalHandler(supervisor *containerd.Supervisor, bufferSize int) {
 	logrus.Debug("containerd: starting signal handler")
 	signals := make(chan os.Signal, bufferSize)
@@ -73,8 +59,5 @@ func reap() (exits []*containerd.Event, err error) {
 }
 
 func setSubReaper() error {
-	if _, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, PR_SET_CHILD_SUBREAPER, 1, 0); err != 0 {
+	return util.SetSubreaper(1)
-		return err
-	}
-	return nil
 }

util/prctl.go

@@ -0,0 +1,43 @@
+// + build linux
+
+// http://man7.org/linux/man-pages/man2/prctl.2.html
+package util
+
+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
+}