[sanitizer] Simplify sanitizer_stoptheworld_test

compiler-rt/lib/sanitizer_common/tests/sanitizer_stoptheworld_test.cpp

@@ -15,6 +15,7 @@
 #include "sanitizer_common/sanitizer_platform.h"
 #if SANITIZER_LINUX && defined(__x86_64__)
 
+#  include <atomic>
 #  include <mutex>
 #  include <thread>
 
@@ -24,22 +25,20 @@
 
 namespace __sanitizer {
 
-static std::mutex incrementer_thread_exit_mutex;
+static std::mutex mutex;
 
 struct CallbackArgument {
-  volatile int counter;
-  volatile bool threads_stopped;
-  volatile bool callback_executed;
-  CallbackArgument()
-      : counter(0), threads_stopped(false), callback_executed(false) {}
+  std::atomic_int counter = {};
+  std::atomic_bool threads_stopped = {};
+  std::atomic_bool callback_executed = {};
 };
 
 void IncrementerThread(CallbackArgument &callback_argument) {
   while (true) {
-    __sync_fetch_and_add(&callback_argument.counter, 1);
+    callback_argument.counter++;
 
-    if (incrementer_thread_exit_mutex.try_lock()) {
-      incrementer_thread_exit_mutex.unlock();
+    if (mutex.try_lock()) {
+      mutex.unlock();
       return;
     }
 
@@ -53,11 +52,10 @@ void Callback(const SuspendedThreadsList &suspended_threads_list,
               void *argument) {
   CallbackArgument *callback_argument = (CallbackArgument *)argument;
   callback_argument->callback_executed = true;
-  int counter_at_init = __sync_fetch_and_add(&callback_argument->counter, 0);
+  int counter_at_init = callback_argument->counter;
   for (uptr i = 0; i < 1000; i++) {
     std::this_thread::yield();
-    if (__sync_fetch_and_add(&callback_argument->counter, 0) !=
-        counter_at_init) {
+    if (callback_argument->counter != counter_at_init) {
       callback_argument->threads_stopped = false;
       return;
     }
@@ -68,10 +66,11 @@ void Callback(const SuspendedThreadsList &suspended_threads_list,
 TEST(StopTheWorld, SuspendThreadsSimple) {
   CallbackArgument argument;
   std::thread thread;
-  incrementer_thread_exit_mutex.lock();
-  ASSERT_NO_THROW(thread = std::thread(IncrementerThread, std::ref(argument)));
+  {
+    std::lock_guard<std::mutex> lock(mutex);
+    thread = std::thread(IncrementerThread, std::ref(argument));
     StopTheWorld(&Callback, &argument);
-  incrementer_thread_exit_mutex.unlock();
+  }
   EXPECT_TRUE(argument.callback_executed);
   EXPECT_TRUE(argument.threads_stopped);
   // argument is on stack, so we have to wait for the incrementer thread to
@@ -84,43 +83,26 @@ TEST(StopTheWorld, SuspendThreadsSimple) {
 static const uptr kThreadCount = 50;
 static const uptr kStopWorldAfter = 10;  // let this many threads spawn first
 
-static std::mutex advanced_incrementer_thread_exit_mutex;
-
 struct AdvancedCallbackArgument {
-  volatile uptr thread_index;
-  volatile int counters[kThreadCount];
+  std::atomic_uintptr_t thread_index = {};
+  std::atomic_int counters[kThreadCount] = {};
   std::thread threads[kThreadCount];
-  volatile bool threads_stopped;
-  volatile bool callback_executed;
-  volatile bool fatal_error;
-  AdvancedCallbackArgument()
-      : thread_index(0),
-        threads_stopped(false),
-        callback_executed(false),
-        fatal_error(false) {}
+  std::atomic_bool threads_stopped = {};
+  std::atomic_bool callback_executed = {};
 };
 
 void AdvancedIncrementerThread(AdvancedCallbackArgument &callback_argument) {
-  uptr this_thread_index =
-      __sync_fetch_and_add(&callback_argument.thread_index, 1);
+  uptr this_thread_index = callback_argument.thread_index++;
   // Spawn the next thread.
   if (this_thread_index + 1 < kThreadCount) {
-    try {
     callback_argument.threads[this_thread_index + 1] =
         std::thread(AdvancedIncrementerThread, std::ref(callback_argument));
-    } catch (...) {
-      // Cannot use ASSERT_EQ in non-void-returning functions. If there's a
-      // problem, defer failing to the main thread.
-      callback_argument.fatal_error = true;
-      __sync_fetch_and_add(&callback_argument.thread_index,
-                           kThreadCount - callback_argument.thread_index);
-    }
   }
   // Do the actual work.
   while (true) {
-    __sync_fetch_and_add(&callback_argument.counters[this_thread_index], 1);
-    if (advanced_incrementer_thread_exit_mutex.try_lock()) {
-      advanced_incrementer_thread_exit_mutex.unlock();
+    callback_argument.counters[this_thread_index]++;
+    if (mutex.try_lock()) {
+      mutex.unlock();
       return;
     }
 
@@ -136,13 +118,11 @@ void AdvancedCallback(const SuspendedThreadsList &suspended_threads_list,
 
   int counters_at_init[kThreadCount];
   for (uptr j = 0; j < kThreadCount; j++)
-    counters_at_init[j] =
-        __sync_fetch_and_add(&callback_argument->counters[j], 0);
+    counters_at_init[j] = callback_argument->counters[j];
   for (uptr i = 0; i < 10; i++) {
     std::this_thread::yield();
     for (uptr j = 0; j < kThreadCount; j++)
-      if (__sync_fetch_and_add(&callback_argument->counters[j], 0) !=
-          counters_at_init[j]) {
+      if (callback_argument->counters[j] != counters_at_init[j]) {
         callback_argument->threads_stopped = false;
         return;
       }
@@ -153,23 +133,21 @@ void AdvancedCallback(const SuspendedThreadsList &suspended_threads_list,
 TEST(StopTheWorld, SuspendThreadsAdvanced) {
   AdvancedCallbackArgument argument;
 
-  advanced_incrementer_thread_exit_mutex.lock();
+  {
+    std::lock_guard<std::mutex> lock(mutex);
     argument.threads[0] =
         std::thread(AdvancedIncrementerThread, std::ref(argument));
     // Wait for several threads to spawn before proceeding.
-  while (__sync_fetch_and_add(&argument.thread_index, 0) < kStopWorldAfter)
-    std::this_thread::yield();
+    while (argument.thread_index < kStopWorldAfter) std::this_thread::yield();
     StopTheWorld(&AdvancedCallback, &argument);
     EXPECT_TRUE(argument.callback_executed);
     EXPECT_TRUE(argument.threads_stopped);
 
     // Wait for all threads to spawn before we start terminating them.
-  while (__sync_fetch_and_add(&argument.thread_index, 0) < kThreadCount)
-    std::this_thread::yield();
-  ASSERT_FALSE(argument.fatal_error);  // a thread could not be started
+    while (argument.thread_index < kThreadCount) std::this_thread::yield();
+  }
   // Signal the threads to terminate.
-  advanced_incrementer_thread_exit_mutex.unlock();
-  for (uptr i = 0; i < kThreadCount; i++) argument.threads[i].join();
+  for (auto &t : argument.threads) t.join();
 }
 
 static void SegvCallback(const SuspendedThreadsList &suspended_threads_list,