Merge branch 'dev_watchdog-less-intrusive'

Eric Dumazet says:

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net: make dev_watchdog() less intrusive

dev_watchdog() is used on many NIC to periodically monitor TX queues
to detect hangs.

Problem is : It stops all queues, then check them, then 'unfreeze' them.

Not only this stops feeding the NIC, it also migrates all qdiscs
to be serviced on the cpu calling netif_tx_unlock(), causing
a potential latency artifact.

With many TX queues, this is becoming more visible.
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Signed-off-by: David S. Miller <davem@davemloft.net>