kern.threads.max_threads_per_proc
kern.threads.max_groups_per_proc
2.Temporary disable borrower thread stash itself as
owner thread's spare thread in thread_exit(). there
is a race between owner thread and borrow thread:
an owner thread may allocate a spare thread as this:
if (td->td_standin == NULL)
td->standin = thread_alloc();
but thread_alloc() can block the thread, then a borrower
thread would possible stash it self as owner's spare
thread in thread_exit(), after owner is resumed, result
is a thread leak in kernel, double check in owner can
avoid the race, but it may be ugly and not worth to do.
7742d9b286