On 2/3/2017 9:56 AM, Eric Dumazet wrote:
On Fri, 2017-02-03 at 09:42 -0800, Shannon Nelson wrote: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 <shannon.nelson@xxxxxxxxxx> --- 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.
Well, it probably should be dma_rmb(), since regardless of the number of cores we think we have, we're communicating with a peer ldom that has its own core(s). Either way, on sparc they all seem to boil down to the same bit of asm, but using the "rmb" part makes more logical sense. I'll respin with dma_rmb().
Good catch, thanks, sln
if (vnet_tx_dring_avail(dr) > VNET_TX_WAKEUP_THRESH(dr)) netif_tx_wake_queue(txq); }
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