code and simply return EINVAL (which is allowed by the standard) in
all those pthread functions that previously initialized it.
o Refactor the pthread_rwlock_[try]rdlock() and pthread_rwlock_[try]wrlock()
functions. They are now completeley condensed into rwlock_rdlock_common()
and rwlock_wrlock_common(), respectively.
o If the application tries to destroy an rwlock that is currently
held by a thread return EBUSY where it previously went ahead and
freed all resources associated with the lock.
o Refactor _pthread_rwlock_init() to make it look (relatively) sane.
o When obtaining a read lock on an rwlock the check for whether it
would exceed the maximum allowed read locks should happen *before*
we obtain the lock.
o The pthread_rwlock_* functions shall *never* return EINTR, so make
sure to requeue/resuspend the thread if it encounters such an error.
o Make a note that pthread_rwlock_unlock() needs to ensure it holds a
lock on an rwlock it tries to unlock. It will be implemented in a
separate commit because it requires some additional rwlock infrastructure.
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