From: Eric Dumazet <redacted>
Date: Wed, 08 Jan 2014 10:09:47 -0800

A physical NIC do not use a workqueue to refill its RX queue but uses
the following strategy :

0) Pre filling of RX ring buffer with N frames. This can use GFP_KERNEL
   allocations with all needed (sleep/retry/shout) logic...
1) IRQ is handled.
2) Can we allocate a new buffer (GFP_ATOMIC) ?
   If yes, we accept the frame,
      and post the new buffer for the 'next frame'
   If no, we drop the frame and recycle the memory for next round.

+1