Re: [PATCH] rwsem: reduce spinlock contention in wakeup code path

[Waiman Long]

On 09/30/2013 03:05 AM, Ingo Molnar wrote:
> * Michel Lespinasse<walken@xxxxxxxxxx>  wrote:
>
> > That said, I am very scared of using rwlock_t here, and I would much
> > prefer we choose a fair lock (either spinlock or a new rwlock
> > implementation which guarantees not to starve any locker thread)
> Given how few users rwlock_t has today we could attempt to make it
> reader-writer fair, as long as the usecase of a hardirq or softirq
> context always getting nested read access on the same CPU is preserved.
>
> (but that can be done - if nothing else then with an explicit context
> check.)
>
> Thanks,
>
> 	Ingo

My queue rwlock patch is able to handle the use case of a hardirq and 
softirq context and can be made almost as fair as the ticket spinlock.

-Longman
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