Re: [XEN PATCH v3 5/5] xen/arm: ffa: support notification

[Julien Grall <julien@xxxxxxx>]

Hi Bertrand,

On 29/04/2024 08:20, Bertrand Marquis wrote:
>  From the comment in sched.h:
> /*
>   * rcu_lock_domain_by_id() is more efficient than get_domain_by_id().
>   * This is the preferred function if the returned domain reference
>   * is short lived,  but it cannot be used if the domain reference needs
>   * to be kept beyond the current scope (e.g., across a softirq).
>   * The returned domain reference must be discarded using rcu_unlock_domain().
>   */
>
> Now the question of short lived should be challenged but I do not think we can
> consider the current code as "long lived".
Actually, I am not entirely sure you can use put_domain() in interrupt 
context. If you look at the implementation of domain_destroy() it takes 
a spin lock without disabling the interrupts.
The same spinlock is taken in domain_create(). So there is a potential 
deadlock.
Which means the decision between the two is not only about liveness.

Cheers,

--
Julien Grall