[PATCH v2] rwlock: Fix explicit hand-over.

[Torvald Riegel]

On Mon, 2017-03-27 at 14:59 -0400, Waiman Long wrote:
> Just found out that there is a regression in performance when in writer
> preferring mode. The average per-thread throughput was 4,733 ops/s with
> the old glibc, but 2,300 ops/s with the new implementation vs 32,584
> ops/s for the reader-preferring mode.

Thanks for the note.  How large is the performance difference for
different numbers of threads?  Is the old rwlock always faster in
writer-preferring mode?