Re: [PATCH v2] xfrm: policy: Read seqcount outside of rcu-read side in xfrm_policy_lookup_bytype

From: Steffen Klassert
Date: Thu Jun 03 2021 - 04:16:48 EST


On Fri, May 28, 2021 at 06:44:37PM +0200, Ahmed S. Darwish wrote:
> On Fri, May 28, 2021, Varad Gautam wrote:
> >
> > Thead 1 (xfrm_hash_resize) Thread 2 (xfrm_policy_lookup_bytype)
> >
> > rcu_read_lock();
> > mutex_lock(&hash_resize_mutex);
> > read_seqcount_begin(&xfrm_policy_hash_generation);
> > mutex_lock(&hash_resize_mutex); // block
> > xfrm_bydst_resize();
> > synchronize_rcu(); // block
> > <RCU stalls in xfrm_policy_lookup_bytype>
> >
> ...
> >
> > Fixes: 77cc278f7b20 ("xfrm: policy: Use sequence counters with associated lock")
> > Signed-off-by: Varad Gautam <varad.gautam@xxxxxxxx>
>
> Acked-by: Ahmed S. Darwish <a.darwish@xxxxxxxxxxxxx>

Applied, thanks a lot!