Files
runc/libcontainer/cgroups/systemd/dbus.go
Kir Kolyshkin e6048715e4 Use gofumpt to format code
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Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
2021-06-01 12:17:27 -07:00

96 lines
2.2 KiB
Go

// +build linux
package systemd
import (
"context"
"sync"
systemdDbus "github.com/coreos/go-systemd/v22/dbus"
dbus "github.com/godbus/dbus/v5"
)
var (
dbusC *systemdDbus.Conn
dbusMu sync.RWMutex
dbusInited bool
dbusRootless bool
)
type dbusConnManager struct{}
// newDbusConnManager initializes systemd dbus connection manager.
func newDbusConnManager(rootless bool) *dbusConnManager {
if dbusInited && rootless != dbusRootless {
panic("can't have both root and rootless dbus")
}
dbusRootless = rootless
return &dbusConnManager{}
}
// getConnection lazily initializes and returns systemd dbus connection.
func (d *dbusConnManager) getConnection() (*systemdDbus.Conn, error) {
// In the case where dbusC != nil
// Use the read lock the first time to ensure
// that Conn can be acquired at the same time.
dbusMu.RLock()
if conn := dbusC; conn != nil {
dbusMu.RUnlock()
return conn, nil
}
dbusMu.RUnlock()
// In the case where dbusC == nil
// Use write lock to ensure that only one
// will be created
dbusMu.Lock()
defer dbusMu.Unlock()
if conn := dbusC; conn != nil {
return conn, nil
}
conn, err := d.newConnection()
if err != nil {
return nil, err
}
dbusC = conn
return conn, nil
}
func (d *dbusConnManager) newConnection() (*systemdDbus.Conn, error) {
if dbusRootless {
return newUserSystemdDbus()
}
return systemdDbus.NewWithContext(context.TODO())
}
// resetConnection resets the connection to its initial state
// (so it can be reconnected if necessary).
func (d *dbusConnManager) resetConnection(conn *systemdDbus.Conn) {
dbusMu.Lock()
defer dbusMu.Unlock()
if dbusC != nil && dbusC == conn {
dbusC.Close()
dbusC = nil
}
}
var errDbusConnClosed = dbus.ErrClosed.Error()
// retryOnDisconnect calls op, and if the error it returns is about closed dbus
// connection, the connection is re-established and the op is retried. This helps
// with the situation when dbus is restarted and we have a stale connection.
func (d *dbusConnManager) retryOnDisconnect(op func(*systemdDbus.Conn) error) error {
for {
conn, err := d.getConnection()
if err != nil {
return err
}
err = op(conn)
if !isDbusError(err, errDbusConnClosed) {
return err
}
d.resetConnection(conn)
}
}