There seems to be some discussion on whether log4net is thread-safe, the consensus is that the framework is thread-safe, but appenders are not and need to be used correctly to a
Straight from the log4net FAQ:
Is log4net thread-safe? Yes, log4net is thread-safe.
Is log4net thread-safe?
Yes, log4net is thread-safe.
So, no need for manual locking.