diff --git a/lib/ExecutionEngine/ExecutionEngine.cpp b/lib/ExecutionEngine/ExecutionEngine.cpp
index f72ddcb..36f7d2f 100644
--- a/lib/ExecutionEngine/ExecutionEngine.cpp
+++ b/lib/ExecutionEngine/ExecutionEngine.cpp
@@ -50,16 +50,18 @@
 /// at the specified address.
 ///
 const GlobalValue *ExecutionEngine::getGlobalValueAtAddress(void *Addr) {
+  MutexGuard locked(lock);
+
   // If we haven't computed the reverse mapping yet, do so first.
-  if (GlobalAddressReverseMap.empty()) {
+  if (state.getGlobalAddressReverseMap(locked).empty()) {
     for (std::map<const GlobalValue*, void *>::iterator I =
-           GlobalAddressMap.begin(), E = GlobalAddressMap.end(); I != E; ++I)
-      GlobalAddressReverseMap.insert(std::make_pair(I->second, I->first));
+           state.getGlobalAddressMap(locked).begin(), E = state.getGlobalAddressMap(locked).end(); I != E; ++I)
+      state.getGlobalAddressReverseMap(locked).insert(std::make_pair(I->second, I->first));
   }
 
   std::map<void *, const GlobalValue*>::iterator I =
-    GlobalAddressReverseMap.find(Addr);
-  return I != GlobalAddressReverseMap.end() ? I->second : 0;
+    state.getGlobalAddressReverseMap(locked).find(Addr);
+  return I != state.getGlobalAddressReverseMap(locked).end() ? I->second : 0;
 }
 
 // CreateArgv - Turn a vector of strings into a nice argv style array of
@@ -168,8 +170,9 @@
   if (Function *F = const_cast<Function*>(dyn_cast<Function>(GV)))
     return getPointerToFunction(F);
 
-  assert(GlobalAddressMap[GV] && "Global hasn't had an address allocated yet?");
-  return GlobalAddressMap[GV];
+  MutexGuard locked(lock);
+  assert(state.getGlobalAddressMap(locked)[GV] && "Global hasn't had an address allocated yet?");
+  return state.getGlobalAddressMap(locked)[GV];
 }
 
 /// FIXME: document
diff --git a/lib/ExecutionEngine/JIT/JIT.cpp b/lib/ExecutionEngine/JIT/JIT.cpp
index cf4e144..d97f197 100644
--- a/lib/ExecutionEngine/JIT/JIT.cpp
+++ b/lib/ExecutionEngine/JIT/JIT.cpp
@@ -30,13 +30,15 @@
 using namespace llvm;
 
 JIT::JIT(ModuleProvider *MP, TargetMachine &tm, TargetJITInfo &tji)
-  : ExecutionEngine(MP), TM(tm), TJI(tji), PM(MP) {
+  : ExecutionEngine(MP), TM(tm), TJI(tji), state(MP) {
   setTargetData(TM.getTargetData());
 
   // Initialize MCE
   MCE = createEmitter(*this);
 
   // Add target data
+  MutexGuard locked(lock);
+  FunctionPassManager& PM = state.getPM(locked);
   PM.add(new TargetData(TM.getTargetData()));
 
   // Compile LLVM Code down to machine code in the intermediate representation
@@ -216,18 +218,20 @@
 void JIT::runJITOnFunction(Function *F) {
   static bool isAlreadyCodeGenerating = false;
   assert(!isAlreadyCodeGenerating && "Error: Recursive compilation detected!");
+	
+  MutexGuard locked(lock);
 
   // JIT the function
   isAlreadyCodeGenerating = true;
-  PM.run(*F);
+  state.getPM(locked).run(*F);
   isAlreadyCodeGenerating = false;
 
   // If the function referred to a global variable that had not yet been
   // emitted, it allocates memory for the global, but doesn't emit it yet.  Emit
   // all of these globals now.
-  while (!PendingGlobals.empty()) {
-    const GlobalVariable *GV = PendingGlobals.back();
-    PendingGlobals.pop_back();
+  while (!state.getPendingGlobals(locked).empty()) {
+    const GlobalVariable *GV = state.getPendingGlobals(locked).back();
+    state.getPendingGlobals(locked).pop_back();
     EmitGlobalVariable(GV);
   }
 }
@@ -236,6 +240,8 @@
 /// specified function, compiling it if neccesary.
 ///
 void *JIT::getPointerToFunction(Function *F) {
+  MutexGuard locked(lock);
+
   if (void *Addr = getPointerToGlobalIfAvailable(F))
     return Addr;   // Check if function already code gen'd
 
@@ -270,6 +276,8 @@
 /// variable, possibly emitting it to memory if needed.  This is used by the
 /// Emitter.
 void *JIT::getOrEmitGlobalVariable(const GlobalVariable *GV) {
+  MutexGuard locked(lock);
+
   void *Ptr = getPointerToGlobalIfAvailable(GV);
   if (Ptr) return Ptr;
 
@@ -287,7 +295,7 @@
     // compilation.
     uint64_t S = getTargetData().getTypeSize(GV->getType()->getElementType());
     Ptr = new char[(size_t)S];
-    PendingGlobals.push_back(GV);
+    state.getPendingGlobals(locked).push_back(GV);
   }
   addGlobalMapping(GV, Ptr);
   return Ptr;
diff --git a/lib/ExecutionEngine/JIT/JIT.h b/lib/ExecutionEngine/JIT/JIT.h
index 3c14cf7..4cce144 100644
--- a/lib/ExecutionEngine/JIT/JIT.h
+++ b/lib/ExecutionEngine/JIT/JIT.h
@@ -27,18 +27,35 @@
 class TargetJITInfo;
 class MachineCodeEmitter;
 
-class JIT : public ExecutionEngine {
-  TargetMachine &TM;       // The current target we are compiling to
-  TargetJITInfo &TJI;      // The JITInfo for the target we are compiling to
-
+class JITState {
+private:
   FunctionPassManager PM;  // Passes to compile a function
-  MachineCodeEmitter *MCE; // MCE object
 
   /// PendingGlobals - Global variables which have had memory allocated for them
   /// while a function was code generated, but which have not been initialized
   /// yet.
   std::vector<const GlobalVariable*> PendingGlobals;
 
+public:
+  JITState(ModuleProvider *MP) : PM(MP) {}
+
+  FunctionPassManager& getPM(const MutexGuard& locked) {
+    return PM;
+  }
+
+  std::vector<const GlobalVariable*>& getPendingGlobals(const MutexGuard& locked) {
+    return PendingGlobals;
+  }
+};
+
+
+class JIT : public ExecutionEngine {
+  TargetMachine &TM;       // The current target we are compiling to
+  TargetJITInfo &TJI;      // The JITInfo for the target we are compiling to
+  MachineCodeEmitter *MCE; // MCE object
+
+  JITState state;
+
   JIT(ModuleProvider *MP, TargetMachine &tm, TargetJITInfo &tji);
 public:
   ~JIT();
diff --git a/lib/ExecutionEngine/JIT/JITEmitter.cpp b/lib/ExecutionEngine/JIT/JITEmitter.cpp
index 301f5e7..47adee0 100644
--- a/lib/ExecutionEngine/JIT/JITEmitter.cpp
+++ b/lib/ExecutionEngine/JIT/JITEmitter.cpp
@@ -120,6 +120,28 @@
 // JIT lazy compilation code.
 //
 namespace {
+  class JITResolverState {
+  private:
+    /// FunctionToStubMap - Keep track of the stub created for a particular
+    /// function so that we can reuse them if necessary.
+    std::map<Function*, void*> FunctionToStubMap;
+
+    /// StubToFunctionMap - Keep track of the function that each stub
+    /// corresponds to.
+    std::map<void*, Function*> StubToFunctionMap;
+  
+  public:
+    std::map<Function*, void*>& getFunctionToStubMap(const MutexGuard& locked) {
+      assert(locked.holds(TheJIT->lock));
+      return FunctionToStubMap;
+    }
+    
+    std::map<void*, Function*>& getStubToFunctionMap(const MutexGuard& locked) {
+      assert(locked.holds(TheJIT->lock));
+      return StubToFunctionMap;
+    }
+  };
+  
   /// JITResolver - Keep track of, and resolve, call sites for functions that
   /// have not yet been compiled.
   class JITResolver {
@@ -130,13 +152,7 @@
     /// rewrite instructions to use.
     TargetJITInfo::LazyResolverFn LazyResolverFn;
 
-    // FunctionToStubMap - Keep track of the stub created for a particular
-    // function so that we can reuse them if necessary.
-    std::map<Function*, void*> FunctionToStubMap;
-
-    // StubToFunctionMap - Keep track of the function that each stub corresponds
-    // to.
-    std::map<void*, Function*> StubToFunctionMap;
+    JITResolverState state;
 
     /// ExternalFnToStubMap - This is the equivalent of FunctionToStubMap for
     /// external functions.
@@ -159,8 +175,9 @@
     /// instruction without the use of a stub, record the location of the use so
     /// we know which function is being used at the location.
     void *AddCallbackAtLocation(Function *F, void *Location) {
+      MutexGuard locked(TheJIT->lock);
       /// Get the target-specific JIT resolver function.
-      StubToFunctionMap[Location] = F;
+      state.getStubToFunctionMap(locked)[Location] = F;
       return (void*)LazyResolverFn;
     }
 
@@ -181,8 +198,10 @@
 /// getFunctionStub - This returns a pointer to a function stub, creating
 /// one on demand as needed.
 void *JITResolver::getFunctionStub(Function *F) {
+  MutexGuard locked(TheJIT->lock);
+
   // If we already have a stub for this function, recycle it.
-  void *&Stub = FunctionToStubMap[F];
+  void *&Stub = state.getFunctionToStubMap(locked)[F];
   if (Stub) return Stub;
 
   // Call the lazy resolver function unless we already KNOW it is an external
@@ -207,7 +226,7 @@
 
   // Finally, keep track of the stub-to-Function mapping so that the
   // JITCompilerFn knows which function to compile!
-  StubToFunctionMap[Stub] = F;
+  state.getStubToFunctionMap(locked)[Stub] = F;
   return Stub;
 }
 
@@ -231,16 +250,21 @@
 void *JITResolver::JITCompilerFn(void *Stub) {
   JITResolver &JR = getJITResolver();
 
+  MutexGuard locked(TheJIT->lock);
+
   // The address given to us for the stub may not be exactly right, it might be
   // a little bit after the stub.  As such, use upper_bound to find it.
   std::map<void*, Function*>::iterator I =
-    JR.StubToFunctionMap.upper_bound(Stub);
-  assert(I != JR.StubToFunctionMap.begin() && "This is not a known stub!");
+    JR.state.getStubToFunctionMap(locked).upper_bound(Stub);
+  assert(I != JR.state.getStubToFunctionMap(locked).begin() && "This is not a known stub!");
   Function *F = (--I)->second;
 
-  // The target function will rewrite the stub so that the compilation callback
-  // function is no longer called from this stub.
-  JR.StubToFunctionMap.erase(I);
+  // We might like to remove the stub from the StubToFunction map.
+  // We can't do that! Multiple threads could be stuck, waiting to acquire the
+  // lock above. As soon as the 1st function finishes compiling the function,
+  // the next one will be released, and needs to be able to find the function it needs
+  // to call.
+  //JR.state.getStubToFunctionMap(locked).erase(I);
 
   DEBUG(std::cerr << "JIT: Lazily resolving function '" << F->getName()
                   << "' In stub ptr = " << Stub << " actual ptr = "
@@ -249,7 +273,7 @@
   void *Result = TheJIT->getPointerToFunction(F);
 
   // We don't need to reuse this stub in the future, as F is now compiled.
-  JR.FunctionToStubMap.erase(F);
+  JR.state.getFunctionToStubMap(locked).erase(F);
 
   // FIXME: We could rewrite all references to this stub if we knew them.
   return Result;