Index: test/tsan/deflake.bash
===================================================================
--- test/tsan/deflake.bash
+++ test/tsan/deflake.bash
@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+# This script is used to deflake inherently flaky tsan tests.
+# It is invoked from lit tests as:
+# $(dirname %s)/deflake.bash %run %t %s
+# The script runs the target program up to 10 times,
+# until it produces the necessary output.
+
+for i in $(seq 1 10); do
+	echo TRY $i
+	not $1 2>&1 | FileCheck $2 && exit 0
+done
+exit 1
Index: test/tsan/simple_race.c
===================================================================
--- test/tsan/simple_race.c
+++ test/tsan/simple_race.c
@@ -1,4 +1,4 @@
-// RUN: %clang_tsan -O1 %s -o %t && not %run %t 2>&1 | FileCheck %s
+// RUN: %clang_tsan -O1 %s -o %t && $(dirname %s)/deflake.bash %run %t %s
 #include <pthread.h>
 #include <stdio.h>
 #include <unistd.h>