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|
// +build linux
package fs
import (
"fmt"
"os"
"path/filepath"
"syscall"
"github.com/docker/libcontainer/cgroups"
)
// NotifyOnOOM sends signals on the returned channel when the cgroup reaches
// its memory limit. The channel is closed when the cgroup is removed.
func NotifyOnOOM(c *cgroups.Cgroup) (<-chan struct{}, error) {
d, err := getCgroupData(c, 0)
if err != nil {
return nil, err
}
return notifyOnOOM(d)
}
func notifyOnOOM(d *data) (<-chan struct{}, error) {
dir, err := d.path("memory")
if err != nil {
return nil, err
}
fd, _, syserr := syscall.RawSyscall(syscall.SYS_EVENTFD2, 0, syscall.FD_CLOEXEC, 0)
if syserr != 0 {
return nil, syserr
}
eventfd := os.NewFile(fd, "eventfd")
oomControl, err := os.Open(filepath.Join(dir, "memory.oom_control"))
if err != nil {
eventfd.Close()
return nil, err
}
var (
eventControlPath = filepath.Join(dir, "cgroup.event_control")
data = fmt.Sprintf("%d %d", eventfd.Fd(), oomControl.Fd())
)
if err := writeFile(dir, "cgroup.event_control", data); err != nil {
eventfd.Close()
oomControl.Close()
return nil, err
}
ch := make(chan struct{})
go func() {
defer func() {
close(ch)
eventfd.Close()
oomControl.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
}
|
