netdev - Re: [PATCH net v4] ovs: limit ovs recursions in ovs_execute

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Message-ID: <569CCAAC.6060906@stressinduktion.org>
Date:	Mon, 18 Jan 2016 12:21:16 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	David Miller <davem@...emloft.net>, pshelar@....org
Cc:	netdev@...r.kernel.org, simon.horman@...ronome.com,
	eric.dumazet@...il.com
Subject: Re: [PATCH net v4] ovs: limit ovs recursions in ovs_execute_actions
 to not corrupt stack

On 18.01.2016 01:26, David Miller wrote:
> From: pravin shelar <pshelar@....org>
> Date: Sat, 16 Jan 2016 09:04:50 -0800
>
>> This function always run in soft-irq context. Do we really need this
>> preempt-disable call here?
>
> Hannes, please respond to this feedback.

Sorry, was traveling on the weekend.

Pravin, I added preempt protection because of the discussion about this 
patch: <http://www.spinics.net/lists/linux-rt-users/msg14343.html>

I didn't want to add a recursion limiter into struct task_struct for 
ovs, so I disable preemption here. On non-rt kernels this will have no 
change in behavior (besides the accesses to the preempt counter), but it 
does the right thing on -rt kernels.

I don't think that -rt kernels are important for openvswitch right now, 
so this is just a safe guard.

Bye,
Hannes