1 files changed, 129 insertions, 0 deletions
diff --git a/pkg/shim/epoll.go b/pkg/shim/epoll.go
new file mode 100644
index 000000000..737d2b781
--- /dev/null
+++ b/pkg/shim/epoll.go
@@ -0,0 +1,129 @@
+// Copyright 2018 The containerd Authors.
+// Copyright 2018 The gVisor 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
+//
+//     https://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.
+
+// +build linux
+
+package shim
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"github.com/containerd/cgroups"
+	"github.com/containerd/containerd/events"
+	"github.com/containerd/containerd/runtime"
+	"golang.org/x/sys/unix"
+)
+
+func newOOMEpoller(publisher events.Publisher) (*epoller, error) {
+	fd, err := unix.EpollCreate1(unix.EPOLL_CLOEXEC)
+	if err != nil {
+		return nil, err
+	}
+	return &epoller{
+		fd:        fd,
+		publisher: publisher,
+		set:       make(map[uintptr]*item),
+	}, nil
+}
+
+type epoller struct {
+	mu sync.Mutex
+
+	fd        int
+	publisher events.Publisher
+	set       map[uintptr]*item
+}
+
+type item struct {
+	id string
+	cg cgroups.Cgroup
+}
+
+func (e *epoller) Close() error {
+	return unix.Close(e.fd)
+}
+
+func (e *epoller) run(ctx context.Context) {
+	var events [128]unix.EpollEvent
+	for {
+		select {
+		case <-ctx.Done():
+			e.Close()
+			return
+		default:
+			n, err := unix.EpollWait(e.fd, events[:], -1)
+			if err != nil {
+				if err == unix.EINTR || err == unix.EAGAIN {
+					continue
+				}
+				// Should not happen.
+				panic(fmt.Errorf("cgroups: epoll wait: %w", err))
+			}
+			for i := 0; i < n; i++ {
+				e.process(ctx, uintptr(events[i].Fd))
+			}
+		}
+	}
+}
+
+func (e *epoller) add(id string, cg cgroups.Cgroup) error {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	fd, err := cg.OOMEventFD()
+	if err != nil {
+		return err
+	}
+	e.set[fd] = &item{
+		id: id,
+		cg: cg,
+	}
+	event := unix.EpollEvent{
+		Fd:     int32(fd),
+		Events: unix.EPOLLHUP | unix.EPOLLIN | unix.EPOLLERR,
+	}
+	return unix.EpollCtl(e.fd, unix.EPOLL_CTL_ADD, int(fd), &event)
+}
+
+func (e *epoller) process(ctx context.Context, fd uintptr) {
+	flush(fd)
+	e.mu.Lock()
+	i, ok := e.set[fd]
+	if !ok {
+		e.mu.Unlock()
+		return
+	}
+	e.mu.Unlock()
+	if i.cg.State() == cgroups.Deleted {
+		e.mu.Lock()
+		delete(e.set, fd)
+		e.mu.Unlock()
+		unix.Close(int(fd))
+		return
+	}
+	if err := e.publisher.Publish(ctx, runtime.TaskOOMEventTopic, &TaskOOM{
+		ContainerID: i.id,
+	}); err != nil {
+		// Should not happen.
+		panic(fmt.Errorf("publish OOM event: %w", err))
+	}
+}
+
+func flush(fd uintptr) error {
+	var buf [8]byte
+	_, err := unix.Read(int(fd), buf[:])
+	return err
+}