Re: Btree runtime recovery. Stuck spins.

> > Hm.  It was OK to use spinlocks to control buffer access when the max
> > delay was just the time to read or write one disk page.  But it sounds
> > like we've pushed the code way past what it was designed to do.  I think
> > this needs some careful thought, not just a quick hack like increasing
> > the timeout interval.
> 
> After thinking more about this, simply increasing S_MAX_BUSY is clearly
> NOT a good answer.  If you are under heavy load then processes that are
> spinning are making things worse, not better, because they are sucking
> CPU cycles that would be better spent on the processes that are holding
> the locks.

Our spinlocks don't go into an infinite test loop, right?  They back off
and retest at random intervals.

I can't imagine we don't have similar btree lock needs other places in
the code were a solution already exists.

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