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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Haiyang Zhang <haiyangz@microsoft.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 5.5 121/176] hv_netvsc: Fix unwanted wakeup in netvsc_attach()
Date:   Tue,  3 Mar 2020 18:43:05 +0100
Message-Id: <20200303174318.789628532@linuxfoundation.org>
In-Reply-To: <20200303174304.593872177@linuxfoundation.org>
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From: Haiyang Zhang <haiyangz@microsoft.com>

commit f6f13c125e05603f68f5bf31f045b95e6d493598 upstream.

When netvsc_attach() is called by operations like changing MTU, etc.,
an extra wakeup may happen while netvsc_attach() calling
rndis_filter_device_add() which sends rndis messages when queue is
stopped in netvsc_detach(). The completion message will wake up queue 0.

We can reproduce the issue by changing MTU etc., then the wake_queue
counter from "ethtool -S" will increase beyond stop_queue counter:
     stop_queue: 0
     wake_queue: 1
The issue causes queue wake up, and counter increment, no other ill
effects in current code. So we didn't see any network problem for now.

To fix this, initialize tx_disable to true, and set it to false when
the NIC is ready to be attached or registered.

Fixes: 7b2ee50c0cd5 ("hv_netvsc: common detach logic")
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/net/hyperv/netvsc.c     |    2 +-
 drivers/net/hyperv/netvsc_drv.c |    3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -99,7 +99,7 @@ static struct netvsc_device *alloc_net_d
 
 	init_waitqueue_head(&net_device->wait_drain);
 	net_device->destroy = false;
-	net_device->tx_disable = false;
+	net_device->tx_disable = true;
 
 	net_device->max_pkt = RNDIS_MAX_PKT_DEFAULT;
 	net_device->pkt_align = RNDIS_PKT_ALIGN_DEFAULT;
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -977,6 +977,7 @@ static int netvsc_attach(struct net_devi
 	}
 
 	/* In any case device is now ready */
+	nvdev->tx_disable = false;
 	netif_device_attach(ndev);
 
 	/* Note: enable and attach happen when sub-channels setup */
@@ -2354,6 +2355,8 @@ static int netvsc_probe(struct hv_device
 	else
 		net->max_mtu = ETH_DATA_LEN;
 
+	nvdev->tx_disable = false;
+
 	ret = register_netdevice(net);
 	if (ret != 0) {
 		pr_err("Unable to register netdev.\n");