From 0ca79c8677debc81a44ea6b21156c72383a7c6a3 Mon Sep 17 00:00:00 2001
From: Zhao Zhili <zhilizhao@tencent.com>
Date: Wed, 4 Sep 2024 21:38:49 +0800
Subject: [PATCH 1/2] add CallOnce

---
 src/platform.h.in       | 57 +++++++++++++++++++++++++++++++++++++++++
 tests/CMakeLists.txt    |  1 +
 tests/test_platform.cpp | 33 ++++++++++++++++++++++++
 3 files changed, 91 insertions(+)
 create mode 100644 tests/test_platform.cpp

diff --git a/src/platform.h.in b/src/platform.h.in
index 50a9454b7da0..732b2f0871b0 100644
--- a/src/platform.h.in
+++ b/src/platform.h.in
@@ -77,6 +77,9 @@
 #else
 #include <pthread.h>
 #endif
+#if (__cplusplus >= 201103L) && !NCNN_SIMPLESTL
+#include <mutex>
+#endif
 #endif // NCNN_THREADS
 
 #if __ANDROID_API__ >= 26
@@ -141,6 +144,22 @@ public:
 private:
     DWORD key;
 };
+
+#if (__cplusplus < 201103L) || NCNN_SIMPLESTL
+typedef INIT_ONCE OnceFlag;
+#define OnceFlagInit INIT_ONCE_STATIC_INIT
+
+static inline int CallOnce(OnceFlag &flag, void (*init_routine)(void))
+{
+    BOOL pending = FALSE;
+    InitOnceBeginInitialize(&flag, 0, &pending, NULL);
+    if (pending)
+        init_routine();
+    InitOnceComplete(&flag, 0, NULL);
+    return 0;
+}
+#endif // < c++11
+
 #else // defined _WIN32
 class NCNN_EXPORT Mutex
 {
@@ -186,7 +205,30 @@ public:
 private:
     pthread_key_t key;
 };
+
+#if (__cplusplus < 201103L) || NCNN_SIMPLESTL
+typedef pthread_once_t OnceFlag;
+#define OnceFlagInit PTHREAD_ONCE_INIT
+
+static inline int CallOnce(OnceFlag &flag, void (*init_routine)(void))
+{
+    return pthread_once(&flag, init_routine);
+}
+#endif // < c++11
+
 #endif // defined _WIN32
+
+#if (__cplusplus >= 201103L) && !NCNN_SIMPLESTL
+using OnceFlag = std::once_flag;
+#define OnceFlagInit {}
+
+static inline int CallOnce(OnceFlag &flag, void (*init_routine)(void))
+{
+    std::call_once(flag, init_routine);
+    return 0;
+}
+#endif // >= c++11
+
 #else // NCNN_THREADS
 class NCNN_EXPORT Mutex
 {
@@ -225,6 +267,21 @@ public:
 private:
     void* data;
 };
+
+typedef bool OnceFlag;
+#define OnceFlagInit false
+
+static inline int CallOnce(OnceFlag &flag, void (*init_routine)(void))
+{
+    if (!flag)
+    {
+        init_routine();
+        flag = true;
+    }
+
+    return 0;
+}
+
 #endif // NCNN_THREADS
 
 class NCNN_EXPORT MutexLockGuard
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index e2ddc32a00dc..44634959dd51 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -60,6 +60,7 @@ endif()
 
 ncnn_add_test(c_api)
 ncnn_add_test(cpu)
+ncnn_add_test(platform)
 
 if(NCNN_VULKAN)
     ncnn_add_test(command)
diff --git a/tests/test_platform.cpp b/tests/test_platform.cpp
new file mode 100644
index 000000000000..21f59ba61853
--- /dev/null
+++ b/tests/test_platform.cpp
@@ -0,0 +1,33 @@
+#include <stdlib.h>
+
+#include "platform.h"
+
+static int g_once_count = 0;
+
+static void init()
+{
+    g_once_count++;
+}
+
+int test_call_once()
+{
+    static ncnn::OnceFlag flag = OnceFlagInit;
+    ncnn::CallOnce(flag, &init);
+    ncnn::CallOnce(flag, &init);
+    ncnn::CallOnce(flag, &init);
+
+    if (g_once_count != 1)
+        return EXIT_FAILURE;
+    return EXIT_SUCCESS;
+}
+
+int main()
+{
+    int ret;
+
+    ret = test_call_once();
+    if (ret)
+        return ret;
+
+    return 0;
+}

From decbf28b3ef5b06c148f72e05b8bcba52b7b555c Mon Sep 17 00:00:00 2001
From: Zhao Zhili <zhilizhao@tencent.com>
Date: Wed, 4 Sep 2024 21:50:56 +0800
Subject: [PATCH 2/2] make try_initialize_global_cpu_info thread safe

---
 src/cpu.cpp | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/src/cpu.cpp b/src/cpu.cpp
index f9e64a1cc75b..b6a3e37913ee 100644
--- a/src/cpu.cpp
+++ b/src/cpu.cpp
@@ -1932,15 +1932,10 @@ static void initialize_global_cpu_info()
 #endif // defined __ANDROID__ || defined __linux__
 }
 
-static int g_cpu_info_initialized = 0;
-
 static inline void try_initialize_global_cpu_info()
 {
-    if (!g_cpu_info_initialized)
-    {
-        initialize_global_cpu_info();
-        g_cpu_info_initialized = 1;
-    }
+    static ncnn::OnceFlag flag = OnceFlagInit;
+    ncnn::CallOnce(flag, &initialize_global_cpu_info);
 }
 
 namespace ncnn {