The original commit was reverted because of the problems it introduced
on Linux. However, FreeBSD should not be affected, so restore that part
and we will address Linux separately.
While at it, remove the dbreg hack as the underlying issue has been
fixed in the FreeBSD kernel and the problem is unlikely to happen
in real life use anyway.
Differential Revision: https://reviews.llvm.org/D98822
This commit has caused the following tests to be flaky:
TestThreadSpecificBpPlusCondition.py
TestExitDuringExpression.py
The exact cause is not known yet, but since both tests deal with
threads, my guess is it has something to do with the tracking of
creation of new threads (which the commit touches upon).
This reverts the following commits:
d01bff8cbdc98fb8751f7bf10af19b47ae5c445d,
ba62ebc48e8c424ce3a78ba01acda679d536dd47,
e761b6b4c58d4f7ae1073d925d7cb321d68ee93a,
a345419ee03095c8cdfbe1c2728467c4da8fa0a4.
