Fix cross-build for memcg notification

pkg/kubelet/eviction/threshold_notifier_linux.go

@@ -0,0 +1,119 @@
+/*
+Copyright 2016 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package eviction
+
+/*
+#include <sys/eventfd.h>
+*/
+import "C"
+
+import (
+	"fmt"
+	"syscall"
+
+	"github.com/golang/glog"
+)
+
+type memcgThresholdNotifier struct {
+	watchfd     int
+	controlfd   int
+	eventfd     int
+	handler     thresholdNotifierHandlerFunc
+	description string
+}
+
+var _ ThresholdNotifier = &memcgThresholdNotifier{}
+
+// NewMemCGThresholdNotifier sends notifications when a cgroup threshold
+// is crossed (in either direction) for a given cgroup attribute
+func NewMemCGThresholdNotifier(path, attribute, threshold, description string, handler thresholdNotifierHandlerFunc) (ThresholdNotifier, error) {
+	watchfd, err := syscall.Open(fmt.Sprintf("%s/%s", path, attribute), syscall.O_RDONLY, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		if err != nil {
+			syscall.Close(watchfd)
+		}
+	}()
+	controlfd, err := syscall.Open(fmt.Sprintf("%s/cgroup.event_control", path), syscall.O_WRONLY, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		if err != nil {
+			syscall.Close(controlfd)
+		}
+	}()
+	efd, err := C.eventfd(0, C.EFD_CLOEXEC)
+	if err != nil {
+		return nil, err
+	}
+	eventfd := int(efd)
+	if eventfd < 0 {
+		err = fmt.Errorf("eventfd call failed")
+		return nil, err
+	}
+	defer func() {
+		if err != nil {
+			syscall.Close(eventfd)
+		}
+	}()
+	glog.V(2).Infof("eviction: setting notification threshold to %s", threshold)
+	config := fmt.Sprintf("%d %d %s", eventfd, watchfd, threshold)
+	_, err = syscall.Write(controlfd, []byte(config))
+	if err != nil {
+		return nil, err
+	}
+	return &memcgThresholdNotifier{
+		watchfd:     watchfd,
+		controlfd:   controlfd,
+		eventfd:     eventfd,
+		handler:     handler,
+		description: description,
+	}, nil
+}
+
+func getThresholdEvents(eventfd int, eventCh chan<- int) {
+	for {
+		buf := make([]byte, 8)
+		_, err := syscall.Read(eventfd, buf)
+		if err != nil {
+			return
+		}
+		eventCh <- 0
+	}
+}
+
+func (n *memcgThresholdNotifier) Start(stopCh <-chan struct{}) {
+	eventCh := make(chan int, 1)
+	go getThresholdEvents(n.eventfd, eventCh)
+	for {
+		select {
+		case <-stopCh:
+			glog.V(2).Infof("eviction: stopping threshold notifier")
+			syscall.Close(n.watchfd)
+			syscall.Close(n.controlfd)
+			syscall.Close(n.eventfd)
+			close(eventCh)
+			return
+		case <-eventCh:
+			glog.V(2).Infof("eviction: threshold crossed")
+			n.handler(n.description)
+		}
+	}
+}