2021-05-28 17:20:57

by Ahmed S. Darwish

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

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 <[email protected]>

Acked-by: Ahmed S. Darwish <[email protected]>

2021-06-03 08:18:47

by Steffen Klassert

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

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 <[email protected]>
>
> Acked-by: Ahmed S. Darwish <[email protected]>

Applied, thanks a lot!