Re: [rfc] "fair" rw spinlocks

[Nick Piggin]

On Sun, Nov 29, 2009 at 10:51:22AM -0800, Paul E. McKenney wrote:
> On Sat, Nov 28, 2009 at 09:30:18AM -0800, Linus Torvalds wrote:
> > So as far as I can tell, we have only one real user of rwlocks where 
> > livelocks might be relevant, but that one real user absolutely _requires_ 
> > the unfair behavior.
> 
> But the required unfairness is limited to unconditionally granting
> recursive read requests, right?  If I understand correctly, if a given
> CPU does not already read-hold the lock, then we can safely make that
> CPU wait for a writer that might otherwise be starved.  Again, is there
> another requirement that I am missing?

I think this is the only ordering requirement.

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