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: a7c44247f70 ("xfrm: policy: make xfrm_policy_lookup_bytype lockless")
Minor note: the 'Fixes' commit should be 77cc278f7b20 ("xfrm: policy:
Use sequence counters with associated lock") instead.
The reason read_seqcount_begin() is emitting a mutex_lock() on
PREEMPT_RT is because of the s/seqcount_t/seqcount_mutex_t/ change.
Kind regards,
--
Ahmed S. Darwish
Linutronix GmbH
