linux-kernel - Re: [PATCH RT] net: move xmit_recursion to per-task variable on -RT

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Message-ID: <56982895.6070901@stressinduktion.org>
Date:	Fri, 15 Jan 2016 00:00:37 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>, netdev@...r.kernel.org
Subject: Re: [PATCH RT] net: move xmit_recursion to per-task variable on -RT

On 14.01.2016 23:20, Eric Dumazet wrote:
> On Thu, 2016-01-14 at 23:02 +0100, Hannes Frederic Sowa wrote:
>
>> We are just adding a second recursion limit solely to openvswitch which
>> has the same problem:
>>
>> https://patchwork.ozlabs.org/patch/566769/
>>
>> This time also we depend on rcu_read_lock marking the section being
>> nonpreemptible. Nice would be a more generic solution here which doesn't
>> need to always add something to *current.
>
>
> Note that rcu_read_lock() does not imply that preemption is disabled.

Exactly, it is conditional on CONFIG_PREEMPT_CPU/CONFIG_PREMPT_COUNT but 
haven't thought about exactly that in this moment.

I will resend this patch with better protection.

Thanks Eric!