lkml.org 
[lkml]   [2017]   [Feb]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH net-next 5/9] sunvnet: add memory barrier before check for tx enable
From
Date
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@oracle.com>
>> ---
>> 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);
>> }
>
>

\
 
 \ /
  Last update: 2017-02-03 22:21    [W:0.074 / U:0.216 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site