Use Eventfd() from x/sys/unix

Use unix.Eventfd() instead of C.eventfd and also use the correct
corresponding unix.EFD_CLOEXEC flag. This allows to get rid of cgo.

pkg/kubelet/eviction/BUILD

@@ -4,23 +4,10 @@ licenses(["notice"])
 
 load(
     "@io_bazel_rules_go//go:def.bzl",
-    "cgo_genrule",
     "go_library",
     "go_test",
 )
 
-cgo_genrule(
-    name = "cgo_codegen",
-    srcs = ["threshold_notifier_linux.go"],
-    clinkopts = [
-        "-lz",
-        "-lm",
-        "-lpthread",
-        "-ldl",
-    ],
-    tags = ["automanaged"],
-)
-
 go_test(
     name = "go_default_test",
     srcs = [
@@ -53,9 +40,9 @@ go_library(
         "doc.go",
         "eviction_manager.go",
         "helpers.go",
+        "threshold_notifier_linux.go",
         "types.go",
     ],
-    library = ":cgo_codegen",
     tags = ["automanaged"],
     deps = [
         "//pkg/api:go_default_library",

pkg/kubelet/eviction/threshold_notifier_linux.go

@@ -1,5 +1,3 @@
-// +build cgo
-
 /*
 Copyright 2016 The Kubernetes Authors.
 
@@ -18,11 +16,6 @@ limitations under the License.
 
 package eviction
 
-/*
-#include <sys/eventfd.h>
-*/
-import "C"
-
 import (
 	"fmt"
 
@@ -61,11 +54,10 @@ func NewMemCGThresholdNotifier(path, attribute, threshold, description string, h
 			unix.Close(controlfd)
 		}
 	}()
-	efd, err := C.eventfd(0, C.EFD_CLOEXEC)
+	eventfd, err := unix.Eventfd(0, unix.EFD_CLOEXEC)
 	if err != nil {
 		return nil, err
 	}
-	eventfd := int(efd)
 	if eventfd < 0 {
 		err = fmt.Errorf("eventfd call failed")
 		return nil, err