From 9e11ca8096a57cda6d91741c064b362180ff2a50 Mon Sep 17 00:00:00 2001
From: gangliao <liaogang@baidu.com>
Date: Mon, 10 Oct 2016 10:15:07 +0800
Subject: [PATCH] Use C++ 11 atomic_flag in MacOS as spin lock (#175)

* Use C++ 11 atomic_flag in MacOS as spin lock
* Add unittest for it.
---
 paddle/trainer/tests/test_CompareSparse.cpp |  2 +-
 paddle/utils/arch/osx/Locks.cpp             | 24 ++-------
 paddle/utils/tests/CMakeLists.txt           |  1 +
 paddle/utils/tests/test_SpinLock.cpp        | 57 +++++++++++++++++++++
 4 files changed, 63 insertions(+), 21 deletions(-)
 create mode 100644 paddle/utils/tests/test_SpinLock.cpp

diff --git a/paddle/trainer/tests/test_CompareSparse.cpp b/paddle/trainer/tests/test_CompareSparse.cpp
index ff37d7b36..311dd333a 100644
--- a/paddle/trainer/tests/test_CompareSparse.cpp
+++ b/paddle/trainer/tests/test_CompareSparse.cpp
@@ -57,7 +57,7 @@ std::vector<ParameterPtr> trainerOnePassTest(const string& configFile,
             << " sparseUpdate=" << sparseUpdate;
   srand(FLAGS_seed);
   *ThreadLocalRand::getSeed() = FLAGS_seed;
-
+  ThreadLocalRandomEngine::get().seed(FLAGS_seed);
   if (useGpu) {
     CHECK_LE(trainerCount, gNumDevices);
   }
diff --git a/paddle/utils/arch/osx/Locks.cpp b/paddle/utils/arch/osx/Locks.cpp
index 44bab7198..b3ec45497 100644
--- a/paddle/utils/arch/osx/Locks.cpp
+++ b/paddle/utils/arch/osx/Locks.cpp
@@ -15,12 +15,9 @@ limitations under the License. */
 #include "paddle/utils/Locks.h"
 #include "paddle/utils/Logging.h"
 #include <dispatch/dispatch.h>
+#include <atomic>
 #include <libkern/OSAtomic.h>
 
-#if MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_12
-#include <os/lock.h>
-#endif
-
 namespace paddle {
 
 class SemaphorePrivate {
@@ -55,12 +52,7 @@ void Semaphore::post() {
 
 class SpinLockPrivate {
 public:
-#if MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_12
-  os_unfair_lock lock_;
-#else
-  SpinLockPrivate(): lock_(OS_SPINLOCK_INIT) {}
-  OSSpinLock lock_;
-#endif
+  std::atomic_flag lock_ = ATOMIC_FLAG_INIT;
   char padding_[64 - sizeof(lock_)];  // Padding to cache line size
 };
 
@@ -68,19 +60,11 @@ SpinLock::SpinLock(): m(new SpinLockPrivate()) {}
 SpinLock::~SpinLock() { delete m; }
 
 void SpinLock::lock() {
-#if MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_12
-  os_unfair_lock_lock(&m->lock_);
-#else
-  OSSpinLockLock(&m->lock_);
-#endif
+  while (m->lock_.test_and_set(std::memory_order_acquire)) {}
 }
 
 void SpinLock::unlock() {
-#if MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_12
-  os_unfair_lock_unlock(&m->lock_);
-#else
-  OSSpinLockUnlock(&m->lock_);
-#endif
+  m->lock_.clear(std::memory_order_release);
 }
 
 
diff --git a/paddle/utils/tests/CMakeLists.txt b/paddle/utils/tests/CMakeLists.txt
index 51f188939..adf489faf 100644
--- a/paddle/utils/tests/CMakeLists.txt
+++ b/paddle/utils/tests/CMakeLists.txt
@@ -4,6 +4,7 @@ add_simple_unittest(test_Thread)
 add_simple_unittest(test_StringUtils)
 add_simple_unittest(test_CustomStackTrace)
 add_simple_unittest(test_ThreadBarrier)
+add_simple_unittest(test_SpinLock)
 
 add_executable(
     test_CustomStackTracePrint
diff --git a/paddle/utils/tests/test_SpinLock.cpp b/paddle/utils/tests/test_SpinLock.cpp
new file mode 100644
index 000000000..ebc84e0f5
--- /dev/null
+++ b/paddle/utils/tests/test_SpinLock.cpp
@@ -0,0 +1,57 @@
+/* Copyright (c) 2016 Baidu, Inc. All Rights Reserve.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+
+#include <gtest/gtest.h>
+#include <vector>
+#include "paddle/utils/Logging.h"
+#include "paddle/utils/CommandLineParser.h"
+#include "paddle/utils/Util.h"
+#include "paddle/utils/Locks.h"
+
+P_DEFINE_int32(test_thread_num, 100, "testing thread number");
+
+void testNormalImpl(size_t thread_num, const std::function
+    <void(size_t, size_t&, paddle::SpinLock&)>& callback) {
+  paddle::SpinLock mutex;
+  std::vector<std::thread> threads;
+  threads.reserve(thread_num);
+
+  size_t count = 0;
+  for (size_t i = 0; i < thread_num; ++i) {
+      threads.emplace_back([&thread_num, &count, &mutex, &callback]{
+          callback(thread_num, count, mutex);
+      });
+  }
+  for (auto& thread : threads) {
+    thread.join();
+  }
+  // Check whether all threads reach this point or not
+  CHECK_EQ(count, thread_num);
+}
+
+TEST(ThreadSpinLock, normalTest) {
+  for (auto &thread_num : {10, 30, 50 , 100 , 300, 1000}) {
+    testNormalImpl(thread_num, [](size_t thread_num,
+        size_t& count, paddle::SpinLock& mutex){
+        std::lock_guard<paddle::SpinLock> lock(mutex);
+        ++count;
+    });
+  }
+}
+
+int main(int argc, char** argv) {
+  testing::InitGoogleTest(&argc, argv);
+  paddle::initMain(argc, argv);
+  return RUN_ALL_TESTS();
+}
-- 
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