2007/12/11, David Miller <[email protected]>:
> From: "Joonwoo Park" <[email protected]>
> Date: Tue, 11 Dec 2007 18:13:34 +0900
>
> Joonwoo-ssi annyoung haseyo,
Wow Great! :-)
> How can the NAPI_STATE_SCHED bit be cleared externally yet we take
> this list_move_tail() code path?
>
> If NAPI_STATE_SCHED is cleared, work will be zero which will never be
> equal to 'weight', and this we'll never attempt the list_move_tail().
>
> If something clears NAPI_STATE_SCHED meanwhile, we have a serious race
> and your patch is an incomplete bandaid. For example, if it can
> happen, then a case like:
>
> if (test_bit(NAPI_STATE_SCHED, &n->state))
> ... something clears NAPI_STATE_SCHED right now ...
> work = n->poll(n, weight);
>
> can crash too.
>
David,
With your suggestions, I'm feeling a doubt at e1000.
It's seems to me e1000_clean does call netif_rx_complete and returns
non-zero work_done when !netif_running()
So net_rx_action has (work == weight) as true with NAPI_STATE_SCHED cleared.
Here is the e1000_clean.
static int
e1000_clean(struct napi_struct *napi, int budget)
{
/* Keep link state information with original netdev */
if (!netif_carrier_ok(poll_dev))
goto quit_polling;
...
adapter->clean_rx(adapter, &adapter->rx_ring[0],
&work_done, budget);
/* If no Tx and not enough Rx work done, exit the polling mode */
if ((!tx_cleaned && (work_done == 0)) ||
!netif_running(poll_dev)) {
quit_polling:
if (likely(adapter->itr_setting & 3))
e1000_set_itr(adapter);
netif_rx_complete(poll_dev, napi);
e1000_irq_enable(adapter);
}
return work_done;
}
Thanks.
Joonwoo
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