Re: [RFC] hv_netvsc: safer orderly shutdown

Several types of control operations require that the underlying RNDIS
infrastructure be restarted. This patch changes the ordering of the
shutdown to avoid race conditions.
Stop all transmits before doing RNDIS halt. This involves stopping the
network device transmit queues, then waiting for all outstanding
sends before informing host to halt.

Also, check for successful restart of the device when after the
change is done.

For review, not tested on Hyper-V yet.

Signed-off-by: Stephen Hemminger <redacted>
---
 drivers/net/hyperv/netvsc_drv.c   | 40 ++++++++++++++++++++++++++++++---------
 drivers/net/hyperv/rndis_filter.c | 23 +++++++++++-----------
 2 files changed, 42 insertions(+), 21 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index da216ca4f2b2..3afa082e093d 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c

@@ -855,8 +855,10 @@ static int netvsc_set_channels(struct net_device *net,

 	orig = nvdev->num_chn;
 	was_opened = rndis_filter_opened(nvdev);
-	if (was_opened)
+	if (was_opened) {
+		netif_tx_disable(net);
 		rndis_filter_close(nvdev);
+	}

 	memset(&device_info, 0, sizeof(device_info));
 	device_info.num_chn = count;

@@ -881,8 +883,13 @@ static int netvsc_set_channels(struct net_device *net,
 		}
 	}

-	if (was_opened)
-		rndis_filter_open(nvdev);
+	if (was_opened) {
+		ret = rndis_filter_open(nvdev);
+		if (ret)
+			netdev_err(net, "reopening device failed: %d\n", ret);
+		else
+			netif_tx_start_all_queues(net);
+	}

 	/* We may have missed link change notifications */
 	net_device_ctx->last_reconfig = 0;

@@ -971,8 +978,10 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)

 	netif_device_detach(ndev);
 	was_opened = rndis_filter_opened(nvdev);
-	if (was_opened)
+	if (was_opened) {
+		netif_tx_disable(net);
 		rndis_filter_close(nvdev);
+	}

 	memset(&device_info, 0, sizeof(device_info));
 	device_info.ring_size = ring_size;

@@ -1004,8 +1013,13 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 		}
 	}

-	if (was_opened)
-		rndis_filter_open(nvdev);
+	if (was_opened) {
+		ret = rndis_filter_open(nvdev);
+		if (ret)
+			netdev_err(net, "reopening device failed: %d\n", ret);
+		else
+			netif_tx_start_all_queues(net);
+	}

 	netif_device_attach(ndev);

@@ -1547,8 +1561,10 @@ static int netvsc_set_ringparam(struct net_device *ndev,

 	netif_device_detach(ndev);
 	was_opened = rndis_filter_opened(nvdev);
-	if (was_opened)
+	if (was_opened) {
+		netif_tx_disable(net);
 		rndis_filter_close(nvdev);
+	}

 	rndis_filter_device_remove(hdev, nvdev);

@@ -1566,8 +1582,14 @@ static int netvsc_set_ringparam(struct net_device *ndev,
 		}
 	}

-	if (was_opened)
-		rndis_filter_open(nvdev);
+	if (was_opened) {
+		ret = rndis_filter_open(nvdev);
+		if (ret)
+			netdev_err(net, "reopening device failed: %d\n", ret);
+		else
+			netif_tx_start_all_queues(net);
+	}
+
 	netif_device_attach(ndev);

 	/* We may have missed link change notifications */

diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
index 0648eebda829..164f5ffe9c50 100644
--- a/drivers/net/hyperv/rndis_filter.c
+++ b/drivers/net/hyperv/rndis_filter.c

@@ -948,11 +948,20 @@ static void rndis_filter_halt_device(struct rndis_device *dev)
 	struct net_device_context *net_device_ctx = netdev_priv(dev->ndev);
 	struct netvsc_device *nvdev = rtnl_dereference(net_device_ctx->nvdev);

+	/* tell bottom half that deice is being closed */
+	nvdev->destroy = true;
+
+	/* Force flag to be ordered before waiting */
+	wmb();
+
+	/* Wait for all send completions */
+	wait_event(nvdev->wait_drain, netvsc_device_idle(nvdev));
+
 	/* Attempt to do a rndis device halt */
 	request = get_rndis_request(dev, RNDIS_MSG_HALT,
 				RNDIS_MESSAGE_SIZE(struct rndis_halt_request));
 	if (!request)
-		goto cleanup;
+		return;

 	/* Setup the rndis set */
 	halt = &request->request_msg.msg.halt_req;

@@ -963,17 +972,7 @@ static void rndis_filter_halt_device(struct rndis_device *dev)

 	dev->state = RNDIS_DEV_UNINITIALIZED;

-cleanup:
-	nvdev->destroy = true;
-
-	/* Force flag to be ordered before waiting */
-	wmb();
-
-	/* Wait for all send completions */
-	wait_event(nvdev->wait_drain, netvsc_device_idle(nvdev));
-
-	if (request)
-		put_rndis_request(dev, request);
+	put_rndis_request(dev, request);
 }

 static int rndis_filter_open_device(struct rndis_device *dev)