netdev - Re: [PATCH net 2/2] rxrpc: Fix the data

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Date:   Fri, 05 Oct 2018 17:33:20 +0100
From:   David Howells <dhowells@...hat.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     dhowells@...hat.com, netdev@...r.kernel.org,
        linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net 2/2] rxrpc: Fix the data_ready handler

Eric Dumazet <eric.dumazet@...il.com> wrote:

> sk_data_ready is not meant to process packets, it is meant to signal
> to another entity (preferably running in process context and thus with proper
> schedule points, and not blocking BH) that there is data ready to be consumed.

The issue is that I need to route the packets to the appropriate call, and the
BH appears to be the right place to do this, especially as I can quickly parse
and discard certain types of packet right there.

If I move all of this to process context then that adds extra context switches
between the routing process and the destination process.

> Under DOS, it is possible multiple cpus will sk_data_ready in parallel.

Ummm...  I've been led to believe that sk_data_ready will *not* be called in
parallel and that the code it calls can assume non-reentrancy.  Is this not
the case?

What about the patch I attached, whereby I use the encap_rcv() hook.  Do you
say that won't work?

David