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

[Hannes Frederic Sowa]

On 14.01.2016 15:50, Sebastian Andrzej Siewior wrote:
> * Thomas Gleixner | 2016-01-13 18:31:46 [+0100]:
>
> > On Wed, 13 Jan 2016, Sebastian Andrzej Siewior wrote:
> > > +#ifdef CONFIG_PREEMPT_RT_FULL
> > > +static inline int dev_recursion_level(void)
> > > +{
> > > +	return atomic_read(&current->xmit_recursion);
> >
> > Why would you need an atomic here. current does hardly race against itself.
>
> right.

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.

Thanks,
Hannes