X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FSupport%2FManagedStatic.cpp;h=b8fb2841e5256fdf5b08573b8b4368aecfba490f;hb=1736df6ae099e5d6a5e8b40c50d42012fd4b36b5;hp=6de65752b3d638f396a1e235753ea06733ab6635;hpb=51b16f473759c1546acbf308a5d3f3e7bf3ea23c;p=oota-llvm.git

diff --git a/lib/Support/ManagedStatic.cpp b/lib/Support/ManagedStatic.cpp
index 6de65752b3d..b8fb2841e52 100644
--- a/lib/Support/ManagedStatic.cpp
+++ b/lib/Support/ManagedStatic.cpp
@@ -13,37 +13,50 @@
 
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Config/config.h"
-#include "llvm/System/Atomic.h"
-#include "llvm/System/Mutex.h"
+#include "llvm/Support/Atomic.h"
+#include "llvm/Support/Mutex.h"
+#include "llvm/Support/MutexGuard.h"
 #include <cassert>
 using namespace llvm;
 
-static const ManagedStaticBase *StaticList = 0;
+static const ManagedStaticBase *StaticList = nullptr;
 
-static sys::Mutex* ManagedStaticMutex = 0;
+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;
+  return ManagedStaticMutex;
+}
 
 void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
                                               void (*Deleter)(void*)) const {
-  if (ManagedStaticMutex) {
-    ManagedStaticMutex->acquire();
+  assert(Creator);
+  if (llvm_is_multithreaded()) {
+    MutexGuard Lock(getManagedStaticMutex());
 
-    if (Ptr == 0) {
-      void* tmp = Creator ? Creator() : 0;
+    if (!Ptr) {
+      void* tmp = Creator();
 
+      TsanHappensBefore(this);
       sys::MemoryFence();
+
+      // 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();
       DeleterFn = Deleter;
       
       // Add to list of managed statics.
       Next = StaticList;
       StaticList = this;
     }
-
-    ManagedStaticMutex->release();
   } else {
-    assert(Ptr == 0 && DeleterFn == 0 && Next == 0 &&
+    assert(!Ptr && !DeleterFn && !Next &&
            "Partially initialized ManagedStatic!?");
-    Ptr = Creator ? Creator() : 0;
+    Ptr = Creator();
     DeleterFn = Deleter;
   
     // Add to list of managed statics.
@@ -58,34 +71,20 @@ void ManagedStaticBase::destroy() const {
          "Not destroyed in reverse order of construction?");
   // Unlink from list.
   StaticList = Next;
-  Next = 0;
+  Next = nullptr;
 
   // Destroy memory.
   DeleterFn(Ptr);
   
   // Cleanup.
-  Ptr = 0;
-  DeleterFn = 0;
-}
-
-bool llvm::llvm_start_multithreaded() {
-#if LLVM_MULTITHREADED
-  assert(ManagedStaticMutex == 0 && "Multithreaded LLVM already initialized!");
-  ManagedStaticMutex = new sys::Mutex(true);
-  return true;
-#else
-  return false;
-#endif
+  Ptr = nullptr;
+  DeleterFn = nullptr;
 }
 
 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
 void llvm::llvm_shutdown() {
+  MutexGuard Lock(getManagedStaticMutex());
+
   while (StaticList)
     StaticList->destroy();
-
-  if (ManagedStaticMutex) {
-    delete ManagedStaticMutex;
-    ManagedStaticMutex = 0;
-  }
 }
-