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Commit a702349a authored by Julian Wiedmann's avatar Julian Wiedmann Committed by David S. Miller
Browse files

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: default avatarJulian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d528114b

drivers/s390/net/qeth_core_main.c

+2 −1
Original line number Diff line number Diff line
@@ -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 */