FAILED: patch "[PATCH] netvsc: fix deadlock betwen link status and removal" failed to apply to 4.4-stable tree

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: stephen hemminger <[email protected]>
Date: Thu, 24 Aug 2017 16:49:16 -0700
Subject: [PATCH] netvsc: fix deadlock betwen link status and removal

There is a deadlock possible when canceling the link status delayed work queue. The removal process is run with RTNL held, and the link status callback is acquring RTNL.

Resolve the issue by using trylock and rescheduling. If cancel is in process, that block it from happening.

index 0d78727f1a14..d91cbc6c3ca4 100644
@@ -1269,7 +1269,12 @@ static void netvsc_link_change(struct work_struct *w)
 	bool notify = false, reschedule = false;
 	unsigned long flags, next_reconfig, delay;
 
-	rtnl_lock();
+	/* if changes are happening, comeback later */
+	if (!rtnl_trylock()) {
+		schedule_delayed_work(&ndev_ctx->dwork, LINKCHANGE_INT);
+		return;
+	}
+
 	net_device = rtnl_dereference(ndev_ctx->nvdev);
 	if (!net_device)
 		goto out_unlock;