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Date:	Thu, 12 May 2016 14:49:37 +0200
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	netdev@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, devel@...uxdriverproject.org,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>
Subject: [PATCH 5/6] hv_netvsc: synchronize netvsc_change_mtu()/netvsc_set_channels() with netvsc_remove()

When netvsc device is removed during mtu change or channels setup we get
into troubles as both paths are trying to remove the device. Synchronize
them with start_remove flag and rtnl lock.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 drivers/net/hyperv/netvsc_drv.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 393403a..71b9125 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -707,7 +707,7 @@ static int netvsc_set_channels(struct net_device *net,
 	int ret = 0;
 	bool recovering = false;
 
-	if (!nvdev || nvdev->destroy)
+	if (net_device_ctx->start_remove || !nvdev || nvdev->destroy)
 		return -ENODEV;
 
 	num_chn = nvdev->num_chn;
@@ -855,7 +855,7 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 	u32 num_chn;
 	int ret = 0;
 
-	if (nvdev == NULL || nvdev->destroy)
+	if (ndevctx->start_remove || !nvdev || nvdev->destroy)
 		return -ENODEV;
 
 	if (nvdev->nvsp_version >= NVSP_PROTOCOL_VERSION_2)
@@ -1206,7 +1206,12 @@ static int netvsc_remove(struct hv_device *dev)
 	ndev_ctx = netdev_priv(net);
 	net_device = ndev_ctx->nvdev;
 
+	/* Avoid racing with netvsc_change_mtu()/netvsc_set_channels()
+	 * removing the device.
+	 */
+	rtnl_lock();
 	ndev_ctx->start_remove = true;
+	rtnl_unlock();
 
 	cancel_delayed_work_sync(&ndev_ctx->dwork);
 	cancel_work_sync(&ndev_ctx->work);
-- 
2.5.5

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