From 7a8ef1453eb3c0f60d5cdfd36716e5e1f5f67ea3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20S=CC=8Ckoda?= <commits@skodak.org>
Date: Fri, 26 Jul 2013 20:27:36 +0200
Subject: [PATCH] MDL-40891 work around make_writable_directory() race
 condition

You will still get a "PHP Warning:  mkdir(): File exists" but that should not cause any problems on production sites.
---
 lib/setuplib.php | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/lib/setuplib.php b/lib/setuplib.php
index e120a909661..06178412317 100644
--- a/lib/setuplib.php
+++ b/lib/setuplib.php
@@ -1260,10 +1260,15 @@ function make_writable_directory($dir, $exceptiononerror = true) {
 
     if (!file_exists($dir)) {
         if (!mkdir($dir, $CFG->directorypermissions, true)) {
-            if ($exceptiononerror) {
-                throw new invalid_dataroot_permissions($dir.' can not be created, check permissions.');
-            } else {
-                return false;
+            clearstatcache();
+            // There might be a race condition when creating directory.
+            if (!is_dir($dir)) {
+                if ($exceptiononerror) {
+                    throw new invalid_dataroot_permissions($dir.' can not be created, check permissions.');
+                } else {
+                    debugging('Can not create directory: '.$dir, DEBUG_DEVELOPER);
+                    return false;
+                }
             }
         }
     }