[lttng-dev] Deadlock in call_rcu_thread when destroy rculfhash node with nested rculfhash

[Evgeniy Ivanov]

Sorry, found partial answer in docs which state that cds_lfht_destroy
should not be called from a call_rcu thread context. Why does this
limitation exists?

On Wed, Oct 19, 2016 at 12:56 PM, Evgeniy Ivanov <i at eivanov.com> wrote:

> Hi,
>
> Each node of top level rculfhash has nested rculfhash. Some thread clears
> the top level map and then uses rcu_barrier() to wait until everything is
> destroyed (it is done to check leaks). Recently it started to dead lock
> sometimes with following stacks:
>
> Thread1:
>
> __poll
> cds_lfht_destroy    <---- nested map
> ...
> free_Node(rcu_head*)  <----- node of top level map
> call_rcu_thread
>
> Thread2:
>
> syscall
> rcu_barrier_qsbr
> destroy_all
> main
>
>
> Did call_rcu_thread dead lock with barrier thread? Or is it some kind of
> internal deadlock because of nested maps?
>
>
> --
> Cheers,
> Evgeniy
>



-- 
Cheers,
Evgeniy
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