A question about StartSubTransaction

Hi hackers,

I found the StartSubTransaction has the following code:

static void
StartSubTransaction(void)
{
[...]

s->state = TRANS_START;

/*
* Initialize subsystems for new subtransaction
*
* must initialize resource-management stuff first
*/
AtSubStart_Memory();
AtSubStart_ResourceOwner();
AfterTriggerBeginSubXact();

s->state = TRANS_INPROGRESS;

[...]
}

IIRC, AtSubStart_Memory, AtSubStart_ResourceOwner and AfterTriggerBeginSubXact don't
use s->state. Why should we set s->state to TRANS_START and then TRANS_INPROGRESS?

--
Regrads,
Japin Li.
ChengDu WenWu Information Technology Co.,Ltd.