There is a potential race condition on Mac that can lead to crashes when destroying `QNetworkConnectionMonitor`. This issue arises when `QNetworkConnectionMonitorPrivate` has already been destroyed, but is still being accessed through `QNCMP::probeCallback()` from another thread. To fix the issue, a reference counter is used. This counter indicates whether the callback is being used in monitoring. It increases when information is retained (when we set the callback, the info retains to 1) and decreases when information is released (the info releases to 0, when QNCMP object is not used in monitoring). A waitCondition is used to notify all threads when the reference counter reaches zero. The QNCMP::reset function waits until the probeCallback is disconnected and the reference counter is zero. This indicates that the info resource is free, allowing us to safely destroy the QNCMP object. The conditional variable protects the QNetworkConnectionMonitorPrivate object and ensures that the callback is disconnected properly. Fixes: QTBUG-130552 Pick-to: 6.8 6.5 Change-Id: I1259c429e92bc20c382604192243d6d8fadb5c25 Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io> Reviewed-by: Vladimir Belyavsky <belyavskyv@gmail.com>