netdev - Re: [PATCH net] virtio-net: disable NAPI only when enabled during XDP set

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Message-Id: <20180228.122231.1811613646832502397.davem@davemloft.net>
Date:   Wed, 28 Feb 2018 12:22:31 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     jasowang@...hat.com
Cc:     mst@...hat.com, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] virtio-net: disable NAPI only when enabled during
 XDP set

From: Jason Wang <jasowang@...hat.com>
Date: Wed, 28 Feb 2018 18:20:04 +0800

> We try to disable NAPI to prevent a single XDP TX queue being used by
> multiple cpus. But we don't check if device is up (NAPI is enabled),
> this could result stall because of infinite wait in
> napi_disable(). Fixing this by checking device state through
> netif_running() before.
> 
> Fixes: 4941d472bf95b ("virtio-net: do not reset during XDP set")
> Signed-off-by: Jason Wang <jasowang@...hat.com>

Yes, mis-paired NAPI enable/disable are really a pain.

Probably, we can do something in the interfaces or mechanisms to make
this less error prone and less fragile.

Anyways, applied and queued up for -stable, thanks!