Re: [PATCH net 1/4] bnxt: don't lock the tx queue from napi poll
From: Michael Chan <michael.chan@broadcom.com>
Date: 2021-08-11 20:42:58
On Wed, Aug 11, 2021 at 12:32 PM Jakub Kicinski [off-list ref] wrote:
quoted hunk ↗ jump to hunk
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c index 865fcb8cf29f..07827d6b0fec 100644 --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c@@ -730,15 +730,10 @@ static void bnxt_tx_int(struct bnxt *bp, struct bnxt_napi *bnapi, int nr_pkts) */ smp_mb(); - if (unlikely(netif_tx_queue_stopped(txq)) && - (bnxt_tx_avail(bp, txr) > bp->tx_wake_thresh)) { - __netif_tx_lock(txq, smp_processor_id()); - if (netif_tx_queue_stopped(txq) && - bnxt_tx_avail(bp, txr) > bp->tx_wake_thresh && - txr->dev_state != BNXT_DEV_STATE_CLOSING) - netif_tx_wake_queue(txq); - __netif_tx_unlock(txq); - } + if (netif_tx_queue_stopped(txq) && + bnxt_tx_avail(bp, txr) > bp->tx_wake_thresh && + READ_ONCE(txr->dev_state) != BNXT_DEV_STATE_CLOSING)
This can race with bnxt_start_xmit(). bnxt_start_xmit() can also wake up the queue when it sees that descriptors are available. I think this is the reason we added tx locking here. The race may be ok because in the worst case, we will wake up the TX queue when it's not supposed to wakeup. If that happens, bnxt_start_xmit() will return NETDEV_TX_BUSY and stop the queue again when there are not enough TX descriptors.
+ netif_tx_wake_queue(txq); } static struct page *__bnxt_alloc_rx_page(struct bnxt *bp, dma_addr_t *mapping,
Attachments
- smime.p7s [application/pkcs7-signature] 4209 bytes