From: Julian Wiedmann <jwi@linux.ibm.com>
Subject: s390/qeth: fix race in used-buffer accounting
Patch-mainline: v4.19-rc1
Git-commit: a702349a4099cd5a7bab0904689d8e0bf8dcd622
References: FATE#326350, LTC#169511, bsc#1113509
Summary: qeth: performance improvements
Description: This adds recent functional and performance improvements for the
qeth network driver.
Primarily this brings Scatter-Gather support for HiperSockets,
reduced CPU consumption in the L3 IPv4 transmit path for OSA,
improved Promiscuous Mode performance due to IFF_UNICAST_FLT,
support for Scatter-Gather on z/VM virtual NICs, and
support for delayed GRO flushing.
For sanity & stability reasons, this effectively constitutes a
backport of the qeth device driver from 4.19 mainline.
Upstream-Description:
s390/qeth: fix race in used-buffer accounting
By updating q->used_buffers only _after_ do_QDIO() has completed, there
is a potential race against the buffer's TX completion. In the unlikely
case that the TX completion path wins, qeth_qdio_output_handler() would
decrement the counter before qeth_flush_buffers() even incremented it.
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/s390/net/qeth_core_main.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -3505,13 +3505,14 @@ static void qeth_flush_buffers(struct qe
qdio_flags = QDIO_FLAG_SYNC_OUTPUT;
if (atomic_read(&queue->set_pci_flags_count))
qdio_flags |= QDIO_FLAG_PCI_OUT;
+ atomic_add(count, &queue->used_buffers);
+
rc = do_QDIO(CARD_DDEV(queue->card), qdio_flags,
queue->queue_no, index, count);
if (queue->card->options.performance_stats)
queue->card->perf_stats.outbound_do_qdio_time +=
qeth_get_micros() -
queue->card->perf_stats.outbound_do_qdio_start_time;
- atomic_add(count, &queue->used_buffers);
if (rc) {
queue->card->stats.tx_errors += count;
/* ignore temporary SIGA errors without busy condition */