[llvm-commits] [llvm] r118461 - /llvm/trunk/lib/VMCore/Attributes.cpp

[Owen Anderson]

Author: resistor
Date: Mon Nov  8 18:27:03 2010
New Revision: 118461

URL: http://llvm.org/viewvc/llvm-project?rev=118461&view=rev
Log:
Fix PR8441, a race condition in the static attributes list.  While the reference counting was itself threadsafe,
the implicit removal of each object from the global list was not.  Make this operation atomic.

Modified:
    llvm/trunk/lib/VMCore/Attributes.cpp

Modified: llvm/trunk/lib/VMCore/Attributes.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/VMCore/Attributes.cpp?rev=118461&r1=118460&r2=118461&view=diff
==============================================================================
--- llvm/trunk/lib/VMCore/Attributes.cpp (original)
+++ llvm/trunk/lib/VMCore/Attributes.cpp Mon Nov  8 18:27:03 2010
@@ -106,7 +106,10 @@
 // AttributeListImpl Definition
 //===----------------------------------------------------------------------===//
 
+
 namespace llvm {
+static ManagedStatic<sys::SmartMutex<true> > ALMutex;
+
 class AttributeListImpl : public FoldingSetNode {
   sys::cas_flag RefCount;
   
@@ -122,10 +125,15 @@
     RefCount = 0;
   }
   
-  void AddRef() { sys::AtomicIncrement(&RefCount); }
+  void AddRef() {
+    sys::SmartScopedLock<true> Lock(*ALMutex);
+    ++RefCount;
+  }
   void DropRef() {
-    sys::cas_flag old = sys::AtomicDecrement(&RefCount);
-    if (old == 0) delete this;
+    sys::SmartScopedLock<true> Lock(*ALMutex);
+    sys::cas_flag old = RefCount++;
+    if (old == 0)
+      delete this;
   }
   
   void Profile(FoldingSetNodeID &ID) const {
@@ -139,11 +147,10 @@
 };
 }
 
-static ManagedStatic<sys::SmartMutex<true> > ALMutex;
 static ManagedStatic<FoldingSet<AttributeListImpl> > AttributesLists;
 
 AttributeListImpl::~AttributeListImpl() {
-  sys::SmartScopedLock<true> Lock(*ALMutex);
+  // NOTE: Lock must be acquired by caller.
   AttributesLists->RemoveNode(this);
 }