llvm-jitlink fixes

llvm/include/llvm/ExecutionEngine/Orc/TaskDispatch.h

@@ -122,7 +122,7 @@ class DynamicThreadPoolTaskDispatcher : public TaskDispatcher {
   void shutdown() override;
 private:
   std::mutex DispatchMutex;
-  bool Running = true;
+  bool Shutdown = false;
   size_t Outstanding = 0;
   std::condition_variable OutstandingCV;
 

llvm/lib/ExecutionEngine/Orc/TaskDispatch.cpp

@@ -31,6 +31,10 @@ void DynamicThreadPoolTaskDispatcher::dispatch(std::unique_ptr<Task> T) {
   {
     std::lock_guard<std::mutex> Lock(DispatchMutex);
 
+    // Reject new tasks if they're dispatched after a call to shutdown.
+    if (Shutdown)
+      return;
+
     if (IsMaterializationTask) {
 
       // If this is a materialization task and there are too many running
@@ -54,6 +58,14 @@ void DynamicThreadPoolTaskDispatcher::dispatch(std::unique_ptr<Task> T) {
       // Run the task.
       T->run();
 
+      // Reset the task to free any resources. We need this to happen *before*
+      // we notify anyone (via Outstanding) that this thread is done to ensure
+      // that we don't proceed with JIT shutdown while still holding resources.
+      // (E.g. this was causing "Dangling SymbolStringPtr" assertions).
+      T.reset();
+
+      // Check the work queue state and either proceed with the next task or
+      // end this thread.
       std::lock_guard<std::mutex> Lock(DispatchMutex);
       if (!MaterializationTaskQueue.empty()) {
         // If there are any materialization tasks running then steal that work.
@@ -64,7 +76,6 @@ void DynamicThreadPoolTaskDispatcher::dispatch(std::unique_ptr<Task> T) {
           IsMaterializationTask = true;
         }
       } else {
-        // Otherwise decrement work counters.
         if (IsMaterializationTask)
           --NumMaterializationThreads;
         --Outstanding;
@@ -78,7 +89,7 @@ void DynamicThreadPoolTaskDispatcher::dispatch(std::unique_ptr<Task> T) {
 
 void DynamicThreadPoolTaskDispatcher::shutdown() {
   std::unique_lock<std::mutex> Lock(DispatchMutex);
-  Running = false;
+  Shutdown = true;
   OutstandingCV.wait(Lock, [this]() { return Outstanding == 0; });
 }
 #endif

llvm/tools/llvm-jitlink/llvm-jitlink.cpp

@@ -2562,6 +2562,7 @@ int main(int argc, char *argv[]) {
     if (Timers)
       Timers->JITLinkTG.printAll(errs());
     reportLLVMJITLinkError(EntryPoint.takeError());
+    ExitOnErr(S->ES.endSession());
     exit(1);
   }