WEAK_SCOPED_MUTEX_LOCK/WEAK_MUTEX_TRY_LOCK revisited

[masaori335]

WEAK_SCOPED_MUTEX_LOCK and WEAK_MUTEX_TRY_LOCK are introduced to allow the mutex to be a nullptr.

https://github.com/apache/trafficserver/blob/31c15927e66c30566edf5e0e83c6b1bf39e84288/include/iocore/eventsystem/Lock.h#L52-L57

Typical usage is below. https://github.com/apache/trafficserver/blob/31c15927e66c30566edf5e0e83c6b1bf39e84288/src/api/APIHook.cc#L73-L75

However, if we take a look at the Continuation::handleEvent in this case, it has a release assert of the mutex.

https://github.com/apache/trafficserver/blob/31c15927e66c30566edf5e0e83c6b1bf39e84288/include/iocore/eventsystem/Continuation.h#L223-L229

It looks like we don't have reason to use WEAK_ version to allow nullptr in many cases.

[duke8253]

Hmm, I need to think this through a bit. I'm referencing #5879 to keep track of related PRs.