2020-02-21 16:33:43

by Haiyang Zhang

Subject: [net PATCH] hv_netvsc: Fix unwanted wakeup in netvsc_attach()

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 <[email protected]>

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

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index ae3f308..1b320bc 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -99,7 +99,7 @@ static struct netvsc_device *alloc_net_device(void)

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;
diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 65e12cb..2c0a24c 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -1068,6 +1068,7 @@ static int netvsc_attach(struct net_device *ndev,
}

/* In any case device is now ready */
+ nvdev->tx_disable = false;
netif_device_attach(ndev);

/* Note: enable and attach happen when sub-channels setup */
@@ -2476,6 +2477,8 @@ static int netvsc_probe(struct hv_device *dev,
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");
--
1.8.3.1

2020-02-24 00:33:20

by David Miller

Subject: Re: [net PATCH] hv_netvsc: Fix unwanted wakeup in netvsc_attach()

From: Haiyang Zhang <[email protected]>
Date: Fri, 21 Feb 2020 08:32:18 -0800

> 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 <[email protected]>

Applied, thank you.