netdev - Re: [PATCH v2 net-next 1/2] hv_netvsc: fix deadlock on hotplug

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Date:   Mon, 11 Sep 2017 14:21:49 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     stephen@...workplumber.org
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        devel@...uxdriverproject.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next 1/2] hv_netvsc: fix deadlock on hotplug

From: Stephen Hemminger <stephen@...workplumber.org>
Date: Wed,  6 Sep 2017 13:53:05 -0700

> When a virtual device is added dynamically (via host console), then
> the vmbus sends an offer message for the primary channel. The processing
> of this message for networking causes the network device to then
> initialize the sub channels.
> 
> The problem is that setting up the sub channels needs to wait until
> the subsequent subchannel offers have been processed. These offers
> come in on the same ring buffer and work queue as where the primary
> offer is being processed; leading to a deadlock.
> 
> This did not happen in older kernels, because the sub channel waiting
> logic was broken (it wasn't really waiting).
> 
> The solution is to do the sub channel setup in its own work queue
> context that is scheduled by the primary channel setup; and then
> happens later.
> 
> Fixes: 732e49850c5e ("netvsc: fix race on sub channel creation")
> Reported-by: Dexuan Cui <decui@...rosoft.com>
> Signed-off-by: Stephen Hemminger <sthemmin@...rosoft.com>
> ---
> v2 - fix module removal race with new work queue

Applied.