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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/