1 files changed, 14 insertions, 17 deletions
diff --git a/lib/Support/ManagedStatic.cpp b/lib/Support/ManagedStatic.cpp
index 9868207b14ff..7dd31315f90d 100644
--- a/lib/Support/ManagedStatic.cpp
+++ b/lib/Support/ManagedStatic.cpp
@@ -13,20 +13,25 @@
 
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Config/config.h"
-#include "llvm/Support/Atomic.h"
-#include "llvm/Support/Compiler.h"
 #include "llvm/Support/Mutex.h"
 #include "llvm/Support/MutexGuard.h"
+#include "llvm/Support/Threading.h"
 #include <cassert>
 using namespace llvm;
 
 static const ManagedStaticBase *StaticList = nullptr;
+static sys::Mutex *ManagedStaticMutex = nullptr;
+LLVM_DEFINE_ONCE_FLAG(mutex_init_flag);
 
-static sys::Mutex& getManagedStaticMutex() {
+static void initializeMutex() {
+  ManagedStaticMutex = new sys::Mutex();
+}
+
+static sys::Mutex* getManagedStaticMutex() {
   // We need to use a function local static here, since this can get called
   // during a static constructor and we need to guarantee that it's initialized
   // correctly.
-  static sys::Mutex ManagedStaticMutex;
+  llvm::call_once(mutex_init_flag, initializeMutex);
   return ManagedStaticMutex;
 }
 
@@ -34,20 +39,12 @@ void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
                                               void (*Deleter)(void*)) const {
   assert(Creator);
   if (llvm_is_multithreaded()) {
-    MutexGuard Lock(getManagedStaticMutex());
-
-    if (!Ptr) {
-      void* tmp = Creator();
+    MutexGuard Lock(*getManagedStaticMutex());
 
-      TsanHappensBefore(this);
-      sys::MemoryFence();
+    if (!Ptr.load(std::memory_order_relaxed)) {
+      void *Tmp = Creator();
 
-      // This write is racy against the first read in the ManagedStatic
-      // accessors. The race is benign because it does a second read after a
-      // memory fence, at which point it isn't possible to get a partial value.
-      TsanIgnoreWritesBegin();
-      Ptr = tmp;
-      TsanIgnoreWritesEnd();
+      Ptr.store(Tmp, std::memory_order_release);
       DeleterFn = Deleter;
       
       // Add to list of managed statics.
@@ -84,7 +81,7 @@ void ManagedStaticBase::destroy() const {
 
 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
 void llvm::llvm_shutdown() {
-  MutexGuard Lock(getManagedStaticMutex());
+  MutexGuard Lock(*getManagedStaticMutex());
 
   while (StaticList)
     StaticList->destroy();