[bug] child processes stall forever and don't get killed

Hi,

I'm running v1.6-643-gecea2b06d5f3 on RHEL7.3 and I'm seeing an issue
where all child processes stall and none of them is getting killed.
They are usually in a syscalls like read, recv, nanosleep, etc.

I suspect this commit introduced the problem, because any syscall
that started but not completed is now considered to "make progress":

  commit ecf6dfd83d4c886d78d4605163cb8c3f1728db62
  Author: Dave Jones <[email protected]>
  Date:   Fri Aug 12 15:05:01 2016 -0400

    if we haven't done a syscall yet, treat child as "making progress".
    
    Chances are that we haven't been scheduled because some other
    children are hogging the cpu.

I'm seeing more the opposite of what commit above says. Most CPUs
are idle, because N-1 children are stuck in recv/read/...
and last child manages to keep going. Then by a chance it also hits
a syscall that doesn't complete and system stays idle
(after ~hour I gave up waiting).

Regards,
Jan