/usr/share/gocode/src/github.com/opencontainers/runc/libcontainer/notify_linux.go is in golang-github-opencontainers-runc-dev 0.0.8+dfsg-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 | // +build linux
package libcontainer
import (
"fmt"
"io/ioutil"
"os"
"path/filepath"
"syscall"
)
const oomCgroupName = "memory"
type PressureLevel uint
const (
LowPressure PressureLevel = iota
MediumPressure
CriticalPressure
)
func registerMemoryEvent(cgDir string, evName string, arg string) (<-chan struct{}, error) {
evFile, err := os.Open(filepath.Join(cgDir, evName))
if err != nil {
return nil, err
}
fd, _, syserr := syscall.RawSyscall(syscall.SYS_EVENTFD2, 0, syscall.FD_CLOEXEC, 0)
if syserr != 0 {
evFile.Close()
return nil, syserr
}
eventfd := os.NewFile(fd, "eventfd")
eventControlPath := filepath.Join(cgDir, "cgroup.event_control")
data := fmt.Sprintf("%d %d %s", eventfd.Fd(), evFile.Fd(), arg)
if err := ioutil.WriteFile(eventControlPath, []byte(data), 0700); err != nil {
eventfd.Close()
evFile.Close()
return nil, err
}
ch := make(chan struct{})
go func() {
defer func() {
close(ch)
eventfd.Close()
evFile.Close()
}()
buf := make([]byte, 8)
for {
if _, err := eventfd.Read(buf); err != nil {
return
}
// When a cgroup is destroyed, an event is sent to eventfd.
// So if the control path is gone, return instead of notifying.
if _, err := os.Lstat(eventControlPath); os.IsNotExist(err) {
return
}
ch <- struct{}{}
}
}()
return ch, nil
}
// notifyOnOOM returns channel on which you can expect event about OOM,
// if process died without OOM this channel will be closed.
func notifyOnOOM(paths map[string]string) (<-chan struct{}, error) {
dir := paths[oomCgroupName]
if dir == "" {
return nil, fmt.Errorf("path %q missing", oomCgroupName)
}
return registerMemoryEvent(dir, "memory.oom_control", "")
}
func notifyMemoryPressure(paths map[string]string, level PressureLevel) (<-chan struct{}, error) {
dir := paths[oomCgroupName]
if dir == "" {
return nil, fmt.Errorf("path %q missing", oomCgroupName)
}
if level > CriticalPressure {
return nil, fmt.Errorf("invalid pressure level %d", level)
}
levelStr := []string{"low", "medium", "critical"}[level]
return registerMemoryEvent(dir, "memory.pressure_level", levelStr)
}
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