We rely on one variable _dmon.modify_watches shared between thread to
ensure that we don't lock with the dmon polling thread waiting indefinitely
and helding a lock.
To ensure that the polling thread sees modifications done to 'modify_watches'
we use an additional mutex that act as a memory barrier.
Should fix commit bb12f085f3.
When taking the critical section we should always send the
event to wakeup the events thread. In addition use
TryEnterCriticalSection to send the event only if needed
reducing the number of spurious events sent.
Avoid waiting with a finite timeout and wait indefinitely in
dmon thread. When we need to unwatch we send a signal to a special
event meant to wakeup the waiting thread.
Some asserts are placed in case that can effectively occur
so we remove the assertion and we return false. In turn we
adapt the logic accordingly so when false is returned to add
a watch we do not open that directory.
We no longer use in Lite XL recursive directory monitoring as
it was a source of problems.
To enforce this at compile time we use the preprocessor to
remove the implementation of recursive monitoring for the Linux
implementation only.
Francesco Abbate