execute reconfigureDvs_Task(spec) repeatedly on the same spec Version failed

var spec = new VcVMwareDVSConfigSpec();
spec.configVersion = dvs.config.configVersion;

...

dvs.reconfigureDvs_Task(spec);
...
dvs.reconfigureDvs_Task(spec);
 

it failed as the spec version has not changed.

error:can not complete operation due to concurrent modification by another operation.

if I get the new spec version before execute dvs.reconfigureDvs_Task(spec) it can work.

namely it can work with the following scripts:

var spec = new VcVMwareDVSConfigSpec();
spec.configVersion = dvs.config.configVersion;

...

dvs.reconfigureDvs_Task(spec);
...

spec.configVersion = dvs.config.configVersion;
dvs.reconfigureDvs_Task(spec);

But the issue it that I must do some operation in the old spec. So must recofigueDvs in the same spec version twice.

Is anyone familiar with it? Waiting for your help.