Merge pull request #2743 from particle-iot/fix/std-once-reentrancy

Fixes std::call_once reentrancy problem

hal/src/nRF52840/include.mk

@@ -9,6 +9,7 @@ HAL_SRC_INCL_PATH = $(TARGET_HAL_PATH)/src/nRF52840
 
 INCLUDE_DIRS += $(HAL_INCL_NRF52840_PATH)
 INCLUDE_DIRS += $(HAL_INCL_ARMV7_PATH)
+INCLUDE_DIRS += $(TARGET_HAL_PATH)/src/portable/FreeRTOS
 
 ifneq (,$(findstring platform,$(DEPENDENCIES)))
 INCLUDE_DIRS += $(HAL_INCL_NRF52840_PATH)

hal/src/nRF52840/sources.mk

@@ -34,6 +34,7 @@ CPPSRC += $(call target_files,$(HAL_MODULE_PATH)/shared/,*.cpp)
 CPPSRC += $(call target_files,$(HAL_MODULE_PATH)/network/util/,*.cpp)
 
 CSRC += $(TARGET_HAL_PATH)/src/portable/FreeRTOS/heap_4_lock.c
+CPPSRC += $(call target_files,$(TARGET_HAL_PATH)/src/portable/FreeRTOS/bits/,*.cpp)
 
 # ASM source files included in this build.
 ASRC +=

hal/src/nRF52840/bits/gthr-default.h → hal/src/portable/FreeRTOS/bits/gthr-default.h

@@ -14,8 +14,14 @@
 #include <atomic>
 
 typedef int __gthread_key_t;
-typedef std::atomic_flag __gthread_once_t;
 
+typedef enum __gthread_once_state_t {
+    GTHREAD_ONCE_STATE_NOT_INITIALIZED = 0,
+    GTHREAD_ONCE_STATE_RUNNING = 1,
+    GTHREAD_ONCE_STATE_INITIALIZED = 2
+} __gthread_once_state_t;
+
+typedef std::atomic<__gthread_once_state_t> __gthread_once_t;
 
 #define _GLIBCXX_UNUSED __attribute__((unused))
 
@@ -25,14 +31,7 @@ __gthread_active_p (void)
     return 0;
 }
 
-static inline int
-__gthread_once (__gthread_once_t* once, void (*func) (void))
-{
-    if (once->test_and_set(std::memory_order_relaxed) == false) {
-        func();
-    }
-    return 0;
-}
+extern "C" int __gthread_once (__gthread_once_t* once, void (*func) (void));
 
 static inline int _GLIBCXX_UNUSED
 __gthread_key_create (__gthread_key_t *__key _GLIBCXX_UNUSED, void (*__func) (void *) _GLIBCXX_UNUSED)
@@ -106,7 +105,7 @@ __gthread_recursive_mutex_destroy (__gthread_recursive_mutex_t *__mutex)
     return os_mutex_recursive_destroy(*__mutex);
 }
 
-#define __GTHREAD_ONCE_INIT ATOMIC_FLAG_INIT
+#define __GTHREAD_ONCE_INIT ATOMIC_VAR_INIT(GTHREAD_ONCE_STATE_NOT_INITIALIZED)
 #define __GTHREAD_MUTEX_INIT_FUNCTION(mx)  os_mutex_create(mx)
 #define __GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION(mx) os_mutex_recursive_create(mx)
 

hal/src/portable/FreeRTOS/bits/gthr.cpp

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2018 Particle Industries, Inc.  All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <bits/gthr.h>
+#include <mutex>
+#include "scope_guard.h"
+#include "gthr-default.h"
+#include "delay_hal.h"
+
+extern "C" void __once_proxy(void) {
+    std::__once_functor();
+}
+
+namespace std {
+
+extern std::unique_lock<std::mutex>*& __get_once_functor_lock_ptr();
+
+} // std
+
+// XXX/FIXME: std::call_once platform-specific implementations are not exported to the application
+// so we should probably just get rid of std::call_once altogether and replace with a separate implememntation.
+extern "C" int __gthread_once (__gthread_once_t* once, void (*func) (void))
+{
+    if (once->load(std::memory_order_acquire) == GTHREAD_ONCE_STATE_INITIALIZED) {
+        // Short path, already initialized
+        return 0;
+    }
+
+    // Make a local copy, this is a workaround for a non-entrant implementation in libstdc++
+    auto callable = std::__once_functor;
+    auto lock = std::__get_once_functor_lock_ptr();
+    if (lock) {
+        // For consistency
+        std::__set_once_functor_lock_ptr(0);
+        // This won't be relocked in <mutex> std::call_once implementation
+        lock->unlock();
+    }
+    // std::__once_functor() is not usable from this point on, local callable should be used
+
+    auto state = GTHREAD_ONCE_STATE_NOT_INITIALIZED;
+    if (once->compare_exchange_strong(state, GTHREAD_ONCE_STATE_RUNNING,
+            std::memory_order_acq_rel)) {
+        // Switched to initializing/running state
+        callable();
+        once->store(GTHREAD_ONCE_STATE_INITIALIZED, std::memory_order_release);
+    } else {
+        // Wait for some other thread to complete initialization
+        while (once->load(std::memory_order_acquire) == GTHREAD_ONCE_STATE_RUNNING) {
+            HAL_Delay_Milliseconds(0);
+        }
+    }
+
+    return 0;
+}

hal/src/rtl872x/include.mk

@@ -7,6 +7,7 @@ HAL_INCL_RTL872X_PATH = $(TARGET_HAL_PATH)/src/rtl872x
 HAL_SRC_INCL_PATH = $(TARGET_HAL_PATH)/src/rtl872x
 
 INCLUDE_DIRS += $(HAL_INCL_RTL872X_PATH)
+INCLUDE_DIRS += $(TARGET_HAL_PATH)/src/portable/FreeRTOS
 
 ifneq (,$(findstring platform,$(DEPENDENCIES)))
 INCLUDE_DIRS += $(HAL_INCL_RTL872X_PATH)

hal/src/rtl872x/sources.mk

@@ -34,7 +34,7 @@ CPPSRC += $(call target_files,$(HAL_MODULE_PATH)/shared/,*.cpp)
 CPPSRC += $(call target_files,$(HAL_MODULE_PATH)/network/util/,*.cpp)
 
 CSRC += $(TARGET_HAL_PATH)/src/portable/FreeRTOS/heap_5_lock.c
-INCLUDE_DIRS += $(TARGET_HAL_PATH)/src/portable/FreeRTOS
+CPPSRC += $(call target_files,$(TARGET_HAL_PATH)/src/portable/FreeRTOS/bits/,*.cpp)
 
 # ASM source files included in this build.
 ASRC +=

system/src/system_threading.cpp

@@ -121,7 +121,7 @@ namespace std {
         return __once;
     }
 
-    inline std::unique_lock<std::mutex>*& __get_once_functor_lock_ptr()
+    std::unique_lock<std::mutex>*& __get_once_functor_lock_ptr()
     {
       static std::unique_lock<std::mutex>* __once_functor_lock_ptr = 0;
       return __once_functor_lock_ptr;