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From: Eric Dumazet <eric.dumazet@gmail.com>
To: David Howells <dhowells@redhat.com>,
	Eric Dumazet <eric.dumazet@gmail.com>
Cc: netdev@vger.kernel.org, linux-afs@lists.infradead.org,
	linux-kernel@vger.kernel.org, Paolo Abeni <pabeni@redhat.com>
Subject: Re: [PATCH net 2/2] rxrpc: Fix the data_ready handler
Date: Fri, 5 Oct 2018 10:44:36 -0700	[thread overview]
Message-ID: <f423612c-db54-b59d-d2f1-9449bb997106@gmail.com> (raw)
In-Reply-To: <25989.1538757200@warthog.procyon.org.uk>



On 10/05/2018 09:33 AM, David Howells wrote:
> Eric Dumazet <eric.dumazet@gmail.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.

Certainly not for UDP.

TCP input processing uses the socket lock, but UDP is fully parallel.

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

I am kind of busy today, will look at it next week.


      reply	other threads:[~2018-10-05 17:44 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-05 13:42 [PATCH net 0/2] rxrpc: Fixes David Howells
2018-10-05 13:43 ` [PATCH net 1/2] rxrpc: Fix some missed refs to init_net David Howells
2018-10-05 13:43 ` [PATCH net 2/2] rxrpc: Fix the data_ready handler David Howells
2018-10-05 13:52   ` Eric Dumazet
2018-10-05 14:18   ` David Howells
2018-10-05 16:07     ` Eric Dumazet
2018-10-05 16:33     ` David Howells
2018-10-05 17:44       ` Eric Dumazet [this message]

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