From 1ea92aa2d5c779925e54580e2d1d7be702bbb08a Mon Sep 17 00:00:00 2001
From: Ned Batchelder <ned@edx.org>
Date: Wed, 22 Feb 2017 16:39:51 -0500
Subject: [PATCH] Prevent OpenBLAS from spawning worker threads. TNL-6456

The RLIMIT_NPROC limit is per-user so simultaneous student submissions
pile up and overflow the limit.  Setting this environment variable will
prevent spawning any threads (the 1 means only have one threads, the
already existing main thread).
---
 common/lib/capa/capa/safe_exec/safe_exec.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/common/lib/capa/capa/safe_exec/safe_exec.py b/common/lib/capa/capa/safe_exec/safe_exec.py
index b57afbcd0d..cf7863b058 100644
--- a/common/lib/capa/capa/safe_exec/safe_exec.py
+++ b/common/lib/capa/capa/safe_exec/safe_exec.py
@@ -14,6 +14,9 @@ import hashlib
 CODE_PROLOG = """\
 from __future__ import division
 
+import os
+os.environ["OPENBLAS_NUM_THREADS"] = "1"    # See TNL-6456
+
 import random as random_module
 import sys
 random = random_module.Random(%r)