misc/24641: pthread_rwlock_rdlock can deadlock

[Daniel Eischen]

On Mon, 5 Jan 2004, Earl Chew wrote:

> However, it appears counter-intuitive to me that if a thread has already
> acquired a rdlock(), and the rdlock() is recursive, that a subsequent
> call should fail.
> 
> Failure should indicate that the lock could not be acquired. But the
> thread _already_ has the lock! So it's hard to explain why the
> subsequent call should fail (given the requirement that the
> rdlock be recursive).

I committed a fix for this in both libc_r and libkse.