SERVER-7300 Race Condition in FailPoint::setMode

1 files changed, 14 insertions, 1 deletions

diff --git a/src/mongo/util/fail_point.cpp b/src/mongo/util/fail_point.cpp
index 881d8c78329..eca5fd83170 100644
--- a/src/mongo/util/fail_point.cpp
+++ b/src/mongo/util/fail_point.cpp
@@ -62,7 +62,7 @@ namespace mongo {
         _data = extra.copy();
 
         if (_mode != off) {
-            _fpInfo.store(ACTIVE_BIT);
+            enableFailPoint();
         }
     }
 
@@ -70,6 +70,19 @@ namespace mongo {
         return _data;
     }
 
+    void FailPoint::enableFailPoint() {
+        // TODO: Better to replace with a bitwise OR, once available for AU32
+        ValType currentVal = _fpInfo.load();
+        ValType expectedCurrentVal;
+        ValType newVal;
+
+        do {
+            expectedCurrentVal = currentVal;
+            newVal = expectedCurrentVal | ACTIVE_BIT;
+            currentVal = _fpInfo.compareAndSwap(expectedCurrentVal, newVal);
+        } while (expectedCurrentVal != currentVal);
+    }
+
     void FailPoint::disableFailPoint() {
         // TODO: Better to replace with a bitwise AND, once available for AU32
         ValType currentVal = _fpInfo.load();