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Subject: Re: [PATCH v2] xen-netfront: Fix Rx stall during network stress and
 OOM
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        <linux-kernel@vger.kernel.org>
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CC: David Miller <davem@davemloft.net>, <netdev@vger.kernel.org>,
        Wei Liu <wei.liu2@citrix.com>, Paul Durrant <paul.durrant@citrix.com>,
        xen-devel <xen-devel@lists.xen.org>
From: Vineeth Remanan Pillai <vineethp@amazon.com>
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Date: Mon, 30 Jan 2017 08:47:52 -0800
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On 01/29/2017 03:09 PM, Boris Ostrovsky wrote:
>
> There are couple of problems with this patch.
> 1. The 'if' clause now evaluates to true on pretty much every call to 
> xennet_alloc_rx_buffers().
Thanks for catching this. In my testing I did not notice this - mostly 
because of the nature of the workload in my testing.

> 2. It tickles a latent bug during resume where the timer triggers 
> before we re-connect. The trouble is that we now try to dereference 
> queue->rx.sring which is NULL since we disconnect in 
> netfront_resume(). (Curiously, I only observe it with 32-bit guests)
I think we may hit this bug after removing the timer as well. We call 
RING_PUSH_REQUESTS_AND_CHECK_NOTIFY soon after, which also dereference 
queue->rx.sring.

Thanks,
Vineeth