[PATCH 0/1] percpu_rw_semaphore: reimplement to not block thereaders unnecessarily

[Oleg Nesterov]

On 10/30, Oleg Nesterov wrote:
>
> So. down_write/up_right does msleep() and it needs to call
> synchronize_sched() 3 times.
>
> This looks too much. It is not that I am worried about the writers,
> the problem is that the new readers are blocked completely while the
> writer sleeps in msleep/synchronize_sched.
>
> Paul, Mikulas, et al. Could you please look at the new implementation
> below? Completely untested/uncompiled, just for discussion.

I tried to test it, seems to work...

But. I guess the only valid test is: pass the review from Paul/Peter.

Todo:
	- add the lockdep annotations

	- we can speedup the down_write-right-aftet-up_write case

What do you all think?

Oleg.

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