BUG/MEDIUM: threads: fix thread_release() at the end of the rendez-vous point

There is a bug in this function used to release other threads. It leaves
the current thread marked as harmless. If after this another thread does
a thread_isolate(), but before the first one reaches poll(), the second
thread will believe it's alone while it's not.

This must be backported to 1.8 since the rendez-vous point was merged
into 1.8.14.
1 file changed