Re: Real-Time Preemption and RCU

[Ingo Molnar]

* Ingo Molnar <mingo@xxxxxxx> wrote:

> [...] How about something like:
> 
>         void
>         rcu_read_lock(void)
>         {
>                 preempt_disable();
>                 if (current->rcu_read_lock_nesting++ == 0) {
>                         current->rcu_read_lock_ptr =
>                                 &__get_cpu_var(rcu_data).lock;
>                         preempt_enable();
>                         read_lock(current->rcu_read_lock_ptr);
>                 } else
>                         preempt_enable();
>         }
> 
> this would still make it 'statistically scalable' - but is it correct?

thinking some more about it, i believe it's correct, because it picks
one particular CPU's lock and correctly releases that lock.

(read_unlock() is atomic even on PREEMPT_RT, so rcu_read_unlock() is
fine.)

	Ingo
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