3a449bbb69c9a3c3a5bc6a052f2de98ab79be7e9 amended the code to remove acquiring a lock when waking up a condition variable. It is fine to not have a lock associated when waking a condition variable; what I misunderstood was the scope of the lock, which (and this underlines the importance of commenting _what exactly_ a lock protects, for each and ever lock) protected both the buffer as well as the counter of the buffer. This made my reasoning flawed: it is necessary to keep the lock while notifying, otherwise the counterpart could verify the condition isn't satisfied and wait (e.g. see numUsedBytes==0), missing the wake from the other thread (which could arrive between the check and the wait). Amends the previous commit. Change-Id: If7db2d045331f1b33b976fb6bf6aa9117c41678f Pick-to: 5.15 6.2 6.4 6.5 Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>