1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
|
// Copyright 2022 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
//
// 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.
//go:build linux
// +build linux
// Package stopfd provides an type that can be used to signal the stop of a dispatcher.
package stopfd
import (
"fmt"
"golang.org/x/sys/unix"
)
// StopFD is an eventfd used to signal the stop of a dispatcher.
type StopFD struct {
EFD int
}
// New returns a new, initialized StopFD.
func New() (StopFD, error) {
efd, err := unix.Eventfd(0, unix.EFD_NONBLOCK)
if err != nil {
return StopFD{EFD: -1}, fmt.Errorf("failed to create eventfd: %w", err)
}
return StopFD{EFD: efd}, nil
}
// Stop writes to the eventfd and notifies the dispatcher to stop. It does not
// block.
func (sf *StopFD) Stop() {
increment := []byte{1, 0, 0, 0, 0, 0, 0, 0}
if n, err := unix.Write(sf.EFD, increment); n != len(increment) || err != nil {
// There are two possible errors documented in eventfd(2) for writing:
// 1. We are writing 8 bytes and not 0xffffffffffffff, thus no EINVAL.
// 2. stop is only supposed to be called once, it can't reach the limit,
// thus no EAGAIN.
panic(fmt.Sprintf("write(EFD) = (%d, %s), want (%d, nil)", n, err, len(increment)))
}
}
|
