Index: test/asan/lit.cfg
===================================================================
--- test/asan/lit.cfg
+++ test/asan/lit.cfg
@@ -212,5 +212,13 @@
 if config.host_os not in ['Linux', 'Darwin', 'FreeBSD', 'Windows']:
   config.unsupported = True
 
-if config.host_os == 'Darwin' and config.target_arch in ["x86_64", "x86_64h"]:
-  config.parallelism_group = "darwin-64bit-sanitizer"
+if config.host_os == 'Darwin':
+  if config.target_arch in ["x86_64", "x86_64h"]:
+    config.parallelism_group = "darwin-64bit-sanitizer"
+  elif config.ios:
+    # The current implementation of the tools in sanitizer_common/ios_comamnds
+    # do not support parallel execution so force sequential execution of the
+    # tests on iOS devices.
+    config.parallelism_group = "darwin-ios-device-sanitizer"
+    lit_config.warning("ASan ios device test cases being run sequentially")
+    lit_config.parallelism_groups["darwin-ios-device-sanitizer"] = 1
Index: test/tsan/lit.cfg
===================================================================
--- test/tsan/lit.cfg
+++ test/tsan/lit.cfg
@@ -85,5 +85,13 @@
 if config.android:
   config.unsupported = True
 
-if config.host_os == 'Darwin' and config.target_arch in ["x86_64", "x86_64h"]:
-  config.parallelism_group = "darwin-64bit-sanitizer"
+if config.host_os == 'Darwin':
+  if config.target_arch in ["x86_64", "x86_64h"]:
+    config.parallelism_group = "darwin-64bit-sanitizer"
+  elif config.ios:
+    # The current implementation of the tools in sanitizer_common/ios_comamnds
+    # do not support parallel execution so force sequential execution of the
+    # tests on iOS devices.
+    config.parallelism_group = "darwin-ios-device-sanitizer"
+    lit_config.warning("TSan ios device test cases being run sequentially")
+    lit_config.parallelism_groups["darwin-ios-device-sanitizer"] = 1