Re: Kernel 3.7.2 strange warning and short system hang

From: Eric Dumazet
Date: Wed Feb 20 2013 - 14:30:34 EST

On Wed, 2013-02-20 at 12:57 -0500, David Miller wrote:

> I've seen this pattern on several occasions and I have to wonder...
> Do we really require, therefore, every NAPI driver to use dev_kfree_skb_any()
> in it's TX reclaim if it supports netpoll?
> That seems completely bogus.

> netpoll is supposed to provide an execution environment when it invokes
> ->poll() that is identical to the normal NAPI execution. If that would
> be true, then this change above would be completely unnecessary.
> We need to figure out what is the case here, and audit all the NAPI
> drivers to make sure they do the right thing once we know what the
> right thing actually is.

netpoll directly calls n->poll()

(poll_napi() -> poll_one_napi() -> napi->poll(napi, budget) )

Presumably it should not do that if running in interrupt context.

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