Revert "Fix performance of recursive read-write locks"

This reverts commit 666486b3efec871301b82244ec661e1eaa6cca9c, which
removed the QHash that protected against reader recursion
deadlocks. Without this hash, a reader will block on
d->readerWait.wait() until the writer finishes its task. However, the
writer never starts because there's a reader that hasn't released the
lock. That's a deadlock.

Change-Id: I792373bb361db35eb9e5504229c099008821a665
Task-number: QTBUG-47530
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

0 files changed, 0 insertions, 0 deletions