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

[Ferruh Yigit <ferruh.yigit@intel.com>]

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.