3 files changed, 22 insertions, 17 deletions
diff --git a/lib/Support/ManagedStatic.cpp b/lib/Support/ManagedStatic.cpp
index 6a1c2a545a..9d7e99f97f 100644
--- a/lib/Support/ManagedStatic.cpp
+++ b/lib/Support/ManagedStatic.cpp
@@ -15,15 +15,32 @@
 #include "llvm/Config/config.h"
 #include "llvm/Support/Atomic.h"
 #include <cassert>
+#include <mutex>
 using namespace llvm;
 
 static const ManagedStaticBase *StaticList = nullptr;
 
+// ManagedStatics can get created during execution of static constructors.  As a
+// result, we cannot use a global static std::mutex object for the lock since it
+// may not have been constructed.  Instead, we do a call-once initialization of
+// a pointer to a mutex.
+static std::once_flag MutexInitializationFlag;
+static std::recursive_mutex* ManagedStaticMutex = nullptr;
+
+// Not all supported platforms (in particular VS2012) have thread-safe function
+// static initialization, so roll our own.
+static std::recursive_mutex& GetManagedStaticMutex() {
+  std::call_once(MutexInitializationFlag,
+      []() { ManagedStaticMutex = new std::recursive_mutex(); } );
+
+  return *ManagedStaticMutex;
+}
+
 void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
                                               void (*Deleter)(void*)) const {
   assert(Creator);
   if (llvm_is_multithreaded()) {
-    llvm_acquire_global_lock();
+    std::lock_guard<std::recursive_mutex> Lock(GetManagedStaticMutex());
 
     if (!Ptr) {
       void* tmp = Creator();
@@ -43,8 +60,6 @@ void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
       Next = StaticList;
       StaticList = this;
     }
-
-    llvm_release_global_lock();
   } else {
     assert(!Ptr && !DeleterFn && !Next &&
            "Partially initialized ManagedStatic!?");
@@ -75,6 +90,8 @@ void ManagedStaticBase::destroy() const {
 
 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
 void llvm::llvm_shutdown() {
+  std::lock_guard<std::recursive_mutex> Lock(GetManagedStaticMutex());
+
   while (StaticList)
     StaticList->destroy();
 
diff --git a/lib/Support/Threading.cpp b/lib/Support/Threading.cpp
index 1acfa79b11..2358dde0e6 100644
--- a/lib/Support/Threading.cpp
+++ b/lib/Support/Threading.cpp
@@ -21,13 +21,10 @@ using namespace llvm;
 
 static bool multithreaded_mode = false;
 
-static sys::Mutex* global_lock = nullptr;
-
 bool llvm::llvm_start_multithreaded() {
 #if LLVM_ENABLE_THREADS != 0
   assert(!multithreaded_mode && "Already multithreaded!");
   multithreaded_mode = true;
-  global_lock = new sys::Mutex(true);
 
   // We fence here to ensure that all initialization is complete BEFORE we
   // return from llvm_start_multithreaded().
@@ -47,7 +44,6 @@ void llvm::llvm_stop_multithreaded() {
   sys::MemoryFence();
 
   multithreaded_mode = false;
-  delete global_lock;
 #endif
 }
 
@@ -55,14 +51,6 @@ bool llvm::llvm_is_multithreaded() {
   return multithreaded_mode;
 }
 
-void llvm::llvm_acquire_global_lock() {
-  if (multithreaded_mode) global_lock->acquire();
-}
-
-void llvm::llvm_release_global_lock() {
-  if (multithreaded_mode) global_lock->release();
-}
-
 #if LLVM_ENABLE_THREADS != 0 && defined(HAVE_PTHREAD_H)
 #include <pthread.h>
 
diff --git a/lib/Support/Timer.cpp b/lib/Support/Timer.cpp
index 61465ae5e8..210bda754e 100644
--- a/lib/Support/Timer.cpp
+++ b/lib/Support/Timer.cpp
@@ -19,6 +19,7 @@
 #include "llvm/Support/Format.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/Mutex.h"
+#include "llvm/Support/MutexGuard.h"
 #include "llvm/Support/Process.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
@@ -84,14 +85,13 @@ static TimerGroup *getDefaultTimerGroup() {
   sys::MemoryFence();
   if (tmp) return tmp;
   
-  llvm_acquire_global_lock();
+  sys::SmartScopedLock<true> Lock(*TimerLock);
   tmp = DefaultTimerGroup;
   if (!tmp) {
     tmp = new TimerGroup("Miscellaneous Ungrouped Timers");
     sys::MemoryFence();
     DefaultTimerGroup = tmp;
   }
-  llvm_release_global_lock();
 
   return tmp;
 }