Re: [dpdk-stable] [dpdk-dev] [PATCH v4] vmxnet3: fix Rx deadlock

Re: [dpdk-stable] [dpdk-dev] [PATCH v4] vmxnet3: fix Rx deadlock

[Ferruh Yigit]

On 12/19/2016 10:41 AM, Ferruh Yigit wrote:
> On 12/19/2016 9:40 AM, Stefan Puiu wrote:
>> Our use case is that we have an app that needs to keep mbufs around
>> for a while. We've seen cases when calling vmxnet3_post_rx_bufs() from
>> vmxet3_recv_pkts(), it might not succeed to add any mbufs to any RX
>> descriptors (where it returns -err). Since there are no mbufs that the
>> virtual hardware can use, no packets will be received after this; the
>> driver won't refill the mbuf after this so it gets stuck in this
>> state. I call this a deadlock for lack of a better term - the virtual
>> HW waits for free mbufs, while the app waits for the hardware to
>> notify it for data (by flipping the generation bit on the used Rx
>> descriptors). Note that after this, the app can't recover.
>>
>> This fix is a rework of this patch by Marco Lee:
>> http://dpdk.org/dev/patchwork/patch/6575/. I had to forward port
>> it, address review comments and also reverted the allocation
>> failure handling to the first version of the patch
>> (http://dpdk.org/ml/archives/dev/2015-July/022079.html), since
>> that's the only approach that seems to work, and seems to be what
>> other drivers are doing (I checked ixgbe and em). Reusing the mbuf
>> that's getting passed to the application doesn't seem to make
>> sense, and it was causing weird issues in our app. Also, reusing
>> rxm without checking if it's NULL could cause the code to crash.
>>
>> Signed-off-by: Stefan Puiu <stefan.puiu@gmail.com>
> 
> Applied to dpdk-next-net/master, thanks.
> 

CC:stable@dpdk.org