[PATCH 0/3] percpu-rwsem: introduce percpu_rw_semaphore->recursive mode

[Oleg Nesterov]

On 06/24, Oleg Nesterov wrote:
>
> So we need percpu_down_write_dont_block_readers(). I already thought
> about this before, I'll try to make the patch tomorrow on top of your
> changes.

Never say tomorrow...

> This means that we do not need task_struct->cpuhp_ref, but we can't
> avoid livelock we currently have: cpu_hotplug_begin() can never succeed
> if the new readers come fast enough.

Like with any other "recursive" lock.

Peter, I know you don't like the 1st patch. And yes, we could add another
mutex into percpu_rw_semaphore instead. But I think it would be better
to rely on rcu_sync_enter(). As for completion, we can remove it later.
Nevermind, the actual change is 3/3 and it looks simple.

Oleg.

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