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Subject[PATCH] net: gainfar: fix race between issuing and completing Tx
Date
gfar_poll() checked Tx queue status without locking, thus allowing
gfar_start_xmit() to alter it in parallel, which caused hang on every
other nfsroot boot with RT enabled.

This patch raises locking from gfar_clean_tx_ring() up to gfar_poll().
With this change applied, hangs are no longer reproduced.

Signed-off-by: Nikita Yushchenko <nyushchenko@dev.rtsoft.ru>
---
drivers/net/ethernet/freescale/gianfar.c | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index 0343a14..9ac1946 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -2499,7 +2499,6 @@ static void gfar_clean_tx_ring(struct gfar_priv_tx_q *tx_queue)
skb_dirtytx = tx_queue->skb_dirtytx;

while ((skb = tx_queue->tx_skbuff[skb_dirtytx])) {
- unsigned long flags;

frags = skb_shinfo(skb)->nr_frags;

@@ -2561,9 +2560,7 @@ static void gfar_clean_tx_ring(struct gfar_priv_tx_q *tx_queue)
TX_RING_MOD_MASK(tx_ring_size);

howmany++;
- spin_lock_irqsave(&tx_queue->txlock, flags);
tx_queue->num_txbdfree += nr_txbds;
- spin_unlock_irqrestore(&tx_queue->txlock, flags);
}

/* If we freed a buffer, we can restart transmission, if necessary */
@@ -2838,6 +2835,7 @@ static int gfar_poll(struct napi_struct *napi, int budget)
int has_tx_work;
unsigned long rstat_rxf;
int num_act_queues;
+ unsigned long flags;

/* Clear IEVENT, so interrupts aren't called again
* because of the packets that have already arrived
@@ -2854,11 +2852,13 @@ static int gfar_poll(struct napi_struct *napi, int budget)
has_tx_work = 0;
for_each_set_bit(i, &gfargrp->tx_bit_map, priv->num_tx_queues) {
tx_queue = priv->tx_queue[i];
+ spin_lock_irqsave(&tx_queue->txlock, flags);
/* run Tx cleanup to completion */
if (tx_queue->tx_skbuff[tx_queue->skb_dirtytx]) {
gfar_clean_tx_ring(tx_queue);
has_tx_work = 1;
}
+ spin_unlock_irqrestore(&tx_queue->txlock, flags);
}

for_each_set_bit(i, &gfargrp->rx_bit_map, priv->num_rx_queues) {
--
1.7.0.1


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