netdev: octeon_mgmt: Fix race condition freeing TX buffers.

Under heavy load the TX cleanup tasklet and xmit threads would race
and try to free too many buffers.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/net/octeon/octeon_mgmt.c b/drivers/net/octeon/octeon_mgmt.c
index bbbd737210f9..b975a2fad953 100644
--- a/drivers/net/octeon/octeon_mgmt.c
+++ b/drivers/net/octeon/octeon_mgmt.c
@@ -189,12 +189,19 @@ static void octeon_mgmt_clean_tx_buffers(struct octeon_mgmt *p)
 
         mix_orcnt.u64 = cvmx_read_csr(CVMX_MIXX_ORCNT(port));
         while (mix_orcnt.s.orcnt) {
+                spin_lock_irqsave(&p->tx_list.lock, flags);
+
+                mix_orcnt.u64 = cvmx_read_csr(CVMX_MIXX_ORCNT(port));
+
+                if (mix_orcnt.s.orcnt == 0) {
+                        spin_unlock_irqrestore(&p->tx_list.lock, flags);
+                        break;
+                }
+
                 dma_sync_single_for_cpu(p->dev, p->tx_ring_handle,
                                         ring_size_to_bytes(OCTEON_MGMT_TX_RING_SIZE),
                                         DMA_BIDIRECTIONAL);
 
-                spin_lock_irqsave(&p->tx_list.lock, flags);
-
                 re.d64 = p->tx_ring[p->tx_next_clean];
                 p->tx_next_clean =
                         (p->tx_next_clean + 1) % OCTEON_MGMT_TX_RING_SIZE;