netdev - RE: hv_netvsc: WARNING: suspicious RCU usage?

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Message-ID: <PU1P153MB01690E2762549221EE9D960DBFD50@PU1P153MB0169.APCP153.PROD.OUTLOOK.COM>
Date:   Tue, 6 Aug 2019 05:25:48 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Yidong Ren <Yidong.Ren@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "David S. Miller" <davem@...emloft.net>
CC:     "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>
Subject: RE: hv_netvsc: WARNING: suspicious RCU usage?

> From: linux-hyperv-owner@...r.kernel.org
> <linux-hyperv-owner@...r.kernel.org> On Behalf Of Dexuan Cui
> Sent: Monday, August 5, 2019 4:56 PM
> The warning is caused by the rcu_dereference_rtnl() :
> 
> 1239 static void netvsc_get_stats64(struct net_device *net,
> 1240                                struct rtnl_link_stats64 *t)
> 1241 {
> 1242         struct net_device_context *ndev_ctx = netdev_priv(net);
> 1243         struct netvsc_device *nvdev =
> rcu_dereference_rtnl(ndev_ctx->nvdev);
> 
> I think here netvsc_get_stats64() neither holds rcu_read_lock() nor RTNL
> 
> IMO it should call rcu_read_lock()/unlock(), or get RTNL to fix the warning?

I just posted a patch on behalf of Stephen:
[PATCH net] hv_netvsc: Fix a warning of suspicious RCU usage
 
Thanks,
-- Dexuan