diff --git a/runtime/bin/ffi_test/ffi_test_functions.cc b/runtime/bin/ffi_test/ffi_test_functions.cc
index e43bafb..51f7d61 100644
--- a/runtime/bin/ffi_test/ffi_test_functions.cc
+++ b/runtime/bin/ffi_test/ffi_test_functions.cc
@@ -9,9 +9,11 @@
 
 #include <stdarg.h>
 #include <stddef.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <sys/types.h>
 
+#include <cinttypes>
 #include <cmath>
 #include <iostream>
 #include <limits>
@@ -898,7 +900,7 @@
 // Sanity test.
 DART_EXPORT intptr_t TestSimpleAddition(intptr_t (*add)(int, int)) {
   const intptr_t result = add(10, 20);
-  std::cout << "result " << result << "\n";
+  printf("result %" PRIdPTR "\n", result);
   CHECK_EQ(result, 30);
   return 0;
 }
diff --git a/runtime/bin/ffi_test/ffi_test_functions_vmspecific.cc b/runtime/bin/ffi_test/ffi_test_functions_vmspecific.cc
index acb5980..f50c7f4 100644
--- a/runtime/bin/ffi_test/ffi_test_functions_vmspecific.cc
+++ b/runtime/bin/ffi_test/ffi_test_functions_vmspecific.cc
@@ -688,6 +688,7 @@
     *response_length_ = response_length;
 
     printf("C   :     Notify result ready.\n");
+    std::unique_lock<std::mutex> lock(mutex);
     notified = true;
     cv.notify_one();
   }
diff --git a/runtime/vm/compiler/backend/il.cc b/runtime/vm/compiler/backend/il.cc
index fa7891c..b3a5995 100644
--- a/runtime/vm/compiler/backend/il.cc
+++ b/runtime/vm/compiler/backend/il.cc
@@ -2550,7 +2550,7 @@
       break;
 
     case Token::kMOD:
-      if (std::abs(rhs) == 1) {
+      if ((rhs == -1) || (rhs == 1)) {
         return flow_graph->TryCreateConstantReplacementFor(this,
                                                            Object::smi_zero());
       }
diff --git a/samples/ffi/samples_test.dart b/samples/ffi/samples_test.dart
index 954aa9c..b53c5db 100644
--- a/samples/ffi/samples_test.dart
+++ b/samples/ffi/samples_test.dart
@@ -5,6 +5,8 @@
 // This file exercises the sample files so that they are tested.
 //
 // SharedObjects=ffi_test_dynamic_library ffi_test_functions
+// Environment=MSAN_OPTIONS=handle_segv=0:detect_stack_use_after_return=1:allocator_may_return_null=1
+// Environment=TSAN_OPTIONS=handle_segv=0:detect_stack_use_after_return=1:allocator_may_return_null=1
 
 import 'sample_ffi_bitfield.dart' as bitfield;
 import 'sample_ffi_data.dart' as data;
diff --git a/tools/bots/test_matrix.json b/tools/bots/test_matrix.json
index 7491d84..e66e6b7 100644
--- a/tools/bots/test_matrix.json
+++ b/tools/bots/test_matrix.json
@@ -1250,6 +1250,7 @@
       "builders": [
         "vm-asan-linux-release-x64",
         "vm-msan-linux-release-x64",
+        "vm-tsan-linux-release-x64",
         "vm-ubsan-linux-release-x64"
       ],
       "meta": {
@@ -1266,42 +1267,7 @@
         {
           "name": "vm tests",
           "arguments": [
-            "-nvm-${sanitizer}-${system}-${mode}-${arch}",
-            "corelib",
-            "ffi",
-            "language",
-            "lib",
-            "samples",
-            "standalone",
-            "utils",
-            "vm"
-          ],
-          "fileset": "vm",
-          "shards": 4
-        }
-      ]
-    },
-    {
-      "builders": [
-        "vm-tsan-linux-release-x64"
-      ],
-      "meta": {
-        "description": "This configuration is used by the VM/JIT builders with sanitizers."
-      },
-      "steps": [
-        {
-          "name": "build dart",
-          "script": "tools/build.py",
-          "arguments": [
-            "runtime"
-          ]
-        },
-        {
-          "name": "vm tests",
-          "arguments": [
-            "-nvm-${sanitizer}-${system}-${mode}-${arch}",
-            "vm",
-            "standalone"
+            "-nvm-${sanitizer}-${system}-${mode}-${arch}"
           ],
           "fileset": "vm",
           "shards": 8
@@ -1312,6 +1278,7 @@
       "builders": [
         "vm-aot-asan-linux-release-x64",
         "vm-aot-msan-linux-release-x64",
+        "vm-aot-tsan-linux-release-x64",
         "vm-aot-ubsan-linux-release-x64"
       ],
       "meta": {
@@ -1329,40 +1296,10 @@
         {
           "name": "vm tests",
           "arguments": [
-            "-nvm-aot-${sanitizer}-${system}-${mode}-${arch}",
-            "vm",
-            "standalone"
+            "-nvm-aot-${sanitizer}-${system}-${mode}-${arch}"
           ],
           "fileset": "vm",
-          "shards": 4
-        }
-      ]
-    },
-    {
-      "builders": [
-        "vm-aot-tsan-linux-release-x64"
-      ],
-      "meta": {
-        "description": "This configuration is used by the VM/AOT builders with sanitizers."
-      },
-      "steps": [
-        {
-          "name": "build dart",
-          "script": "tools/build.py",
-          "arguments": [
-            "runtime",
-            "runtime_precompiled"
-          ]
-        },
-        {
-          "name": "vm tests",
-          "arguments": [
-            "-nvm-aot-${sanitizer}-${system}-${mode}-${arch}",
-            "vm",
-            "standalone"
-          ],
-          "fileset": "vm",
-          "shards": 8
+          "shards": 12
         }
       ]
     },