[PATCH net-next 5/9] s390/qeth: don't take queue lock in send_packet_fast()

Julian Wiedmann
2017-09-18T19:18:18Z

Locking the output queue prior to TX is needed on OSA devices,
to synchronize against a packing flush from the TX completion code
(via qeth_check_outbound_queue()).
But send_packet_fast() is only used for IQDs, which don't do packing.
So remove the locking, and apply some easy cleanups.

Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Reviewed-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
---
drivers/s390/net/qeth_core.h | 3 +--
drivers/s390/net/qeth_core_main.c | 22 +++++-----------------
drivers/s390/net/qeth_l2_main.c | 2 +-
drivers/s390/net/qeth_l3_main.c | 4 ++--
4 files changed, 9 insertions(+), 22 deletions(-)

diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index e3d3609cd9e7..b7e8531625aa 100644
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -962,8 +962,7 @@ int qeth_get_priority_queue(struct qeth_card *, struct sk_buff *, int, int);
int qeth_get_elements_no(struct qeth_card *card, struct sk_buff *skb,
int extra_elems, int data_offset);
int qeth_get_elements_for_frags(struct sk_buff *);
-int qeth_do_send_packet_fast(struct qeth_card *card,
- struct qeth_qdio_out_q *queue, struct sk_buff *skb,
+int qeth_do_send_packet_fast(struct qeth_qdio_out_q *queue, struct sk_buff *skb,
struct qeth_hdr *hdr, unsigned int offset,
unsigned int hd_len);
int qeth_do_send_packet(struct qeth_card *card, struct qeth_qdio_out_q *queue,
diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index 77032801e30b..68e118f1202e 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -4040,35 +4040,23 @@ static int qeth_fill_buffer(struct qeth_qdio_out_q *queue,
return flush_cnt;
}

-int qeth_do_send_packet_fast(struct qeth_card *card,
- struct qeth_qdio_out_q *queue, struct sk_buff *skb,
+int qeth_do_send_packet_fast(struct qeth_qdio_out_q *queue, struct sk_buff *skb,
struct qeth_hdr *hdr, unsigned int offset,
unsigned int hd_len)
{
- struct qeth_qdio_out_buffer *buffer;
- int index;
+ int index = queue->next_buf_to_fill;
+ struct qeth_qdio_out_buffer *buffer = queue->bufs[index];

- /* spin until we get the queue ... */
- while (atomic_cmpxchg(&queue->state, QETH_OUT_Q_UNLOCKED,
- QETH_OUT_Q_LOCKED) != QETH_OUT_Q_UNLOCKED);
- /* ... now we've got the queue */
- index = queue->next_buf_to_fill;
- buffer = queue->bufs[queue->next_buf_to_fill];
/*
* check if buffer is empty to make sure that we do not 'overtake'
* ourselves and try to fill a buffer that is already primed
*/
if (atomic_read(&buffer->state) != QETH_QDIO_BUF_EMPTY)
- goto out;
- queue->next_buf_to_fill = (queue->next_buf_to_fill + 1) %
- QDIO_MAX_BUFFERS_PER_Q;
- atomic_set(&queue->state, QETH_OUT_Q_UNLOCKED);
+ return -EBUSY;
+ queue->next_buf_to_fill = (index + 1) % QDIO_MAX_BUFFERS_PER_Q;
qeth_fill_buffer(queue, buffer, skb, hdr, offset, hd_len);
qeth_flush_buffers(queue, index, 1);
return 0;
-out:
- atomic_set(&queue->state, QETH_OUT_Q_UNLOCKED);
- return -EBUSY;
}
EXPORT_SYMBOL_GPL(qeth_do_send_packet_fast);

diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c
index 25a0f381bcd5..009de7248cc7 100644
--- a/drivers/s390/net/qeth_l2_main.c
+++ b/drivers/s390/net/qeth_l2_main.c
@@ -698,7 +698,7 @@ static int qeth_l2_xmit_iqd(struct qeth_card *card, struct sk_buff *skb,
rc = -E2BIG;
goto out;
}
- rc = qeth_do_send_packet_fast(card, queue, skb, hdr, data_offset,
+ rc = qeth_do_send_packet_fast(queue, skb, hdr, data_offset,
sizeof(*hdr) + data_offset);
out:
if (rc)
diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index ab661a431f7c..733f94cbd4d4 100644
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -2771,8 +2771,8 @@ static netdev_tx_t qeth_l3_hard_start_xmit(struct sk_buff *skb,
rc = qeth_do_send_packet(card, queue, new_skb, hdr, hd_len,
hd_len, elements);
} else
- rc = qeth_do_send_packet_fast(card, queue, new_skb, hdr,
- data_offset, hd_len);
+ rc = qeth_do_send_packet_fast(queue, new_skb, hdr, data_offset,
+ hd_len);

if (!rc) {
card->stats.tx_packets++;
--
2.13.5