Comment 6 for bug 1864063

To reproduce (on an 8 CPU VM):

sudo apt-get update && sudo apt-get dist-upgrade
sudo apt-get build-dep stress-ng
git clone git://kernel.ubuntu.com/cking/stress-ng
cd stress-ng
make
sudo ./stress-ng --vm-segv 0 -t 10 -v

Comment out a ptrace line and rebuild and re-run and the hang does not occur. So it's ptrace releated.

diff --git a/stress-vm-segv.c b/stress-vm-segv.c
index 39e4cbeb..54d590cd 100644
--- a/stress-vm-segv.c
+++ b/stress-vm-segv.c
@@ -129,7 +129,7 @@ kill_child:
    stress_process_dumpable(false);

 #if defined(HAVE_PTRACE)
- (void)ptrace(PTRACE_TRACEME);
+ //(void)ptrace(PTRACE_TRACEME);
    kill(getpid(), SIGSTOP);
 #endif
    (void)sigemptyset(&set);