Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> writes:
> Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> writes:
>
>> In commit 2a04ae8acb14 ("hv_netvsc: remove locking in netvsc_send()"), the
>> locking for MSD (Multi-Send Data) field was removed. This could cause a
>> race condition between RNDIS control messages and data packets processing,
>> because these two types of traffic are not synchronized.
>> This patch fixes this issue by sending control messages out directly
>> without reading MSD field.
>>
>> Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
>> Reviewed-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
>> ---
>> drivers/net/hyperv/netvsc.c | 9 +++++++++
>> 1 files changed, 9 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
>> index 02bab9a..059fc52 100644
>> --- a/drivers/net/hyperv/netvsc.c
>> +++ b/drivers/net/hyperv/netvsc.c
>> @@ -867,6 +867,14 @@ int netvsc_send(struct hv_device *device,
>> packet->send_buf_index = NETVSC_INVALID_INDEX;
>> packet->cp_partial = false;
>>
>> + /* Send control message directly without accessing msd (Multi-Send
>> + * Data) field which may be changed during data packet processing.
>> + */
>> + if (!skb) {
>> + cur_send = packet;
>> + goto send_now;
>> + }
>> +
>
> Is is supposed to be applied on top of some other patches? It doesn't
> compile on top of current net-next:
>
> drivers/net/hyperv/netvsc.c: In function ‘netvsc_send’:
> drivers/net/hyperv/netvsc.c:865:7: error: ‘skb’ undeclared (first use in
> this function)
> if (!skb) {
> ^
>
> Did you mean to check rndis_msg instead (as skb is not defined here)?
Oh, my bad, it was me who was looking at the wrong branch... Sorry for
the noise.
>
>> msdp = &net_device->msd[q_idx];
>>
>> /* batch packets in send buffer if possible */
>> @@ -939,6 +947,7 @@ int netvsc_send(struct hv_device *device,
>> }
>> }
>>
>> +send_now:
>> if (cur_send)
>> ret = netvsc_send_pkt(cur_send, net_device, pb, skb);
>
> I suppose we untangle these two pathes completely: let
> rndis_filter_send_request() call netvsc_send_pkt() directly. Please see
> my patch attached (note: it should be split in 3 patches if
> submitted). If you like the idea I can send it.
This patch will need some changes but the suggestion still stands: let's
untangle sending data and control messages.
--
Vitaly
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