Prevent Thread Exited/Joined events race
Summary:
Add atomic verification to ensure that Thread is Joined after marking it
Finished.
It is required for NetBSD in order to prevent Thread Exited/Joined race,
that may occur when native system libpthread(3) cannot be reliably traced
in a way to guarantee that the mentioned events happen one after another.
This change fixes at least TSan and LSan on NetBSD.
Sponsored by <The NetBSD Foundation>
Reviewers: joerg, dvyukov, vitalybuka
Reviewed By: dvyukov
Subscribers: llvm-commits, kubamracek, #sanitizers
Tags: #sanitizers
Differential Revision: https://reviews.llvm.org/D40294
llvm-svn: 319004