NETDEV WATCHDOG: eth1 (r8169): transmit queue 0 timed out

https://www.douban.com/note/251201964/

From: http://marc.info/?l=linux-netdev&m=135474171009246&w=2
The watchdog will fire if all these conditions are met:

1. The interface is up

2. A TX queue is stopped (normally because it is full)

3. No packets have been added to the queue in the last 5 seconds

4. The driver has not told the kernel that the device is unable to

transmit now (e.g. link is down).

Conditions 2 and 3 together normally mean that the TX queue has been

stopped for 5 seconds and therefore that few packets (not necessarily

none at all) have been completed in that time. The time taken for

individual packets to be completed is *not* considered.

This can happen due to:

a. Driver bug causing conditions 2 and 4 to be true during

reconfiguration

b. MAC blocked by a pause frame flood

c. IRQ handling is delayed by a long time (can happen due to excessive

serial logging)

d. Firmware bug causes driver to see link as up when it's not

e. Hardware fault (always a possibility)

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Item d should really be expanded to hardware/firmware/software bug.