Fix for memory leak reported by Valgrind

If llvm so lib is dlopened and dlclosed several times, then memory leak can be observed, reported by Valgrind.

This patch fixes the issue.

Reviewed By: lattner, dblaikie

Differential Revision: https://reviews.llvm.org/D83372

diff --git a/llvm/lib/Support/ManagedStatic.cpp b/llvm/lib/Support/ManagedStatic.cpp
index 053493f..a6ae670 100644 (file)
--- a/llvm/lib/Support/ManagedStatic.cpp
+++ b/llvm/lib/Support/ManagedStatic.cpp
@@ -18,16 +18,10 @@
 using namespace llvm;
 
 static const ManagedStaticBase *StaticList = nullptr;
-static std::recursive_mutex *ManagedStaticMutex = nullptr;
-static llvm::once_flag mutex_init_flag;
-
-static void initializeMutex() {
-  ManagedStaticMutex = new std::recursive_mutex();
-}
 
 static std::recursive_mutex *getManagedStaticMutex() {
-  llvm::call_once(mutex_init_flag, initializeMutex);
-  return ManagedStaticMutex;
+  static std::recursive_mutex m;
+  return &m;
 }
 
 void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
@@ -75,9 +69,10 @@ void ManagedStaticBase::destroy() const {
 }
 
 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
+/// IMPORTANT: it's only safe to call llvm_shutdown() in single thread,
+/// without any other threads executing LLVM APIs.
+/// llvm_shutdown() should be the last use of LLVM APIs.
 void llvm::llvm_shutdown() {
-  std::lock_guard<std::recursive_mutex> Lock(*getManagedStaticMutex());
-
   while (StaticList)
     StaticList->destroy();
 }