This is a follow-up to D116372, which had a rather unfortunate side
effect of making the processing of a single SIGCHLD quadratic in the
number of threads -- which does not matter for simple applications, but
can get really bad for applications with thousands of threads.
This patch fixes the problem by implementing the other possibility
mentioned in the first patch -- doing waitpid(-1) centrally and then
routing the events to the correct process instance. The "uncollected"
threads are held in the process factory class -- which I've renamed to
Manager for this purpose, as it now does more than creating processes.
Differential Revision: https://reviews.llvm.org/D146977
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.
Watch for fork(2)/vfork(2) (also fork/vfork-style clone(2) on Linux)
notifications and explicitly detach the forked child process, and add
initial tests for these cases. The code covers FreeBSD, Linux
and NetBSD process plugins. There is no new user-visible functionality
provided -- this change lays foundations over subsequent work on fork
support.
Differential Revision: https://reviews.llvm.org/D98822
