This is a note to let you know that I've just added the patch titled
bnxt: don't lock the tx queue from napi poll
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bnxt-don-t-lock-the-tx-queue-from-napi-poll.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f62a60e55193601b9c2c7c26c72b888d5bc3141d
Author: Jakub Kicinski <kuba@xxxxxxxxxx>
Date: Thu Aug 12 14:42:39 2021 -0700
bnxt: don't lock the tx queue from napi poll
[ Upstream commit 3c603136c9f82833813af77185618de5af67676c ]
We can't take the tx lock from the napi poll routine, because
netpoll can poll napi at any moment, including with the tx lock
already held.
The tx lock is protecting against two paths - the disable
path, and (as Michael points out) the NETDEV_TX_BUSY case
which may occur if NAPI completions race with start_xmit
and both decide to re-enable the queue.
For the disable/ifdown path use synchronize_net() to make sure
closing the device does not race we restarting the queues.
Annotate accesses to dev_state against data races.
For the NAPI cleanup vs start_xmit path - appropriate barriers
are already in place in the main spot where Tx queue is stopped
but we need to do the same careful dance in the TX_BUSY case.
Fixes: c0c050c58d84 ("bnxt_en: New Broadcom ethernet driver.")
Reviewed-by: Michael Chan <michael.chan@xxxxxxxxxxxx>
Reviewed-by: Edwin Peer <edwin.peer@xxxxxxxxxxxx>
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 8f169508a90a..65e41612b9da 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -360,6 +360,26 @@ static u16 bnxt_xmit_get_cfa_action(struct sk_buff *skb)
return md_dst->u.port_info.port_id;
}
+static bool bnxt_txr_netif_try_stop_queue(struct bnxt *bp,
+ struct bnxt_tx_ring_info *txr,
+ struct netdev_queue *txq)
+{
+ netif_tx_stop_queue(txq);
+
+ /* netif_tx_stop_queue() must be done before checking
+ * tx index in bnxt_tx_avail() below, because in
+ * bnxt_tx_int(), we update tx index before checking for
+ * netif_tx_queue_stopped().
+ */
+ smp_mb();
+ if (bnxt_tx_avail(bp, txr) > bp->tx_wake_thresh) {
+ netif_tx_wake_queue(txq);
+ return false;
+ }
+
+ return true;
+}
+
static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct bnxt *bp = netdev_priv(dev);
@@ -387,8 +407,8 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev)
free_size = bnxt_tx_avail(bp, txr);
if (unlikely(free_size < skb_shinfo(skb)->nr_frags + 2)) {
- netif_tx_stop_queue(txq);
- return NETDEV_TX_BUSY;
+ if (bnxt_txr_netif_try_stop_queue(bp, txr, txq))
+ return NETDEV_TX_BUSY;
}
length = skb->len;
@@ -597,16 +617,7 @@ tx_done:
if (netdev_xmit_more() && !tx_buf->is_push)
bnxt_db_write(bp, &txr->tx_db, prod);
- netif_tx_stop_queue(txq);
-
- /* netif_tx_stop_queue() must be done before checking
- * tx index in bnxt_tx_avail() below, because in
- * bnxt_tx_int(), we update tx index before checking for
- * netif_tx_queue_stopped().
- */
- smp_mb();
- if (bnxt_tx_avail(bp, txr) > bp->tx_wake_thresh)
- netif_tx_wake_queue(txq);
+ bnxt_txr_netif_try_stop_queue(bp, txr, txq);
}
return NETDEV_TX_OK;
@@ -690,14 +701,9 @@ next_tx_int:
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);
- }
+ bnxt_tx_avail(bp, txr) > bp->tx_wake_thresh &&
+ READ_ONCE(txr->dev_state) != BNXT_DEV_STATE_CLOSING)
+ netif_tx_wake_queue(txq);
}
static struct page *__bnxt_alloc_rx_page(struct bnxt *bp, dma_addr_t *mapping,
@@ -8885,9 +8891,11 @@ void bnxt_tx_disable(struct bnxt *bp)
if (bp->tx_ring) {
for (i = 0; i < bp->tx_nr_rings; i++) {
txr = &bp->tx_ring[i];
- txr->dev_state = BNXT_DEV_STATE_CLOSING;
+ WRITE_ONCE(txr->dev_state, BNXT_DEV_STATE_CLOSING);
}
}
+ /* Make sure napi polls see @dev_state change */
+ synchronize_net();
/* Drop carrier first to prevent TX timeout */
netif_carrier_off(bp->dev);
/* Stop all TX queues */
@@ -8901,8 +8909,10 @@ void bnxt_tx_enable(struct bnxt *bp)
for (i = 0; i < bp->tx_nr_rings; i++) {
txr = &bp->tx_ring[i];
- txr->dev_state = 0;
+ WRITE_ONCE(txr->dev_state, 0);
}
+ /* Make sure napi polls see @dev_state change */
+ synchronize_net();
netif_tx_wake_all_queues(bp->dev);
if (bp->link_info.link_up)
netif_carrier_on(bp->dev);
