Thread (17 messages) flat view 17 messages, 3 authors, 2017-02-04

Re: [PATCH net-next 5/9] sunvnet: add memory barrier before check for tx enable

From: Eric Dumazet <hidden>
Date: 2017-02-03 17:57:07
Also in: lkml, sparclinux

On Fri, 2017-02-03 at 09:42 -0800, Shannon Nelson wrote:
quoted hunk ↗ jump to hunk
In order to allow the underlying LDC and outstanding memory operations
to potentially catch up with the driver's Tx requests, add a memory
barrier before checking again for available tx descriptors.

Signed-off-by: Shannon Nelson <redacted>
---
 drivers/net/ethernet/sun/sunvnet_common.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/drivers/net/ethernet/sun/sunvnet_common.c b/drivers/net/ethernet/sun/sunvnet_common.c
index 5d0d386..98e758e 100644
--- a/drivers/net/ethernet/sun/sunvnet_common.c
+++ b/drivers/net/ethernet/sun/sunvnet_common.c
@@ -1467,6 +1467,7 @@ ldc_start_done:
 	dr->prod = (dr->prod + 1) & (VNET_TX_RING_SIZE - 1);
 	if (unlikely(vnet_tx_dring_avail(dr) < 1)) {
 		netif_tx_stop_queue(txq);
+		dma_wmb();
This does not look right.

I believe you need smp_rmb() here.
 		if (vnet_tx_dring_avail(dr) > VNET_TX_WAKEUP_THRESH(dr))
 			netif_tx_wake_queue(txq);
 	}
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