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s390/qeth: fix race in used-buffer accounting

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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>
This commit is contained in:
Julian Wiedmann 2018-07-19 12:43:48 +02:00 committed by David S. Miller
parent d528114bd3
commit a702349a40
1 changed files with 2 additions and 1 deletions
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3
drivers/s390/net/qeth_core_main.c
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@ -3506,13 +3506,14 @@ static void qeth_flush_buffers(struct qeth_qdio_out_q *queue, int index,
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 */