Guard C API polling by thread state

Author: fangerer

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/cext/capi/transitions/CApiTransitions.java

@@ -454,10 +454,22 @@ public static int pollReferenceQueue() {
         if (handleContext.referenceQueuePollingState != RQ_READY) {
             return manuallyCollected;
         }
+        /*
+         * Polling the reference queue may deallocate native GC objects and therefore re-enter
+         * native code paths that use '_PyThreadState_GET()' to obtain the current thread's GC
+         * state. So, we may only poll once the current thread has installed its native
+         * 'tstate_current' pointer.
+         */
+        if (!context.getThreadState(context.getLanguage()).isNativeThreadStateInitialized()) {
+            return manuallyCollected;
+        }
         try (GilNode.UncachedAcquire ignored = GilNode.uncachedAcquire()) {
             if (handleContext.referenceQueuePollingState != RQ_READY) {
                 return manuallyCollected;
             }
+            if (!context.getThreadState(context.getLanguage()).isNativeThreadStateInitialized()) {
+                return manuallyCollected;
+            }
             ReferenceQueue<Object> queue = handleContext.referenceQueue;
             int count = 0;
             long start = 0;

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/PythonContext.java

@@ -592,6 +592,10 @@ public void setNativeThreadLocalVarPointer(Object ptr) {
                             String.format("ptr = %s; nativeThreadLocalVarPointer = %s", ptr, nativeThreadLocalVarPointer);
             this.nativeThreadLocalVarPointer = ptr;
         }
+
+        public boolean isNativeThreadStateInitialized() {
+            return nativeThreadLocalVarPointer != null;
+        }
     }
 
     private static final class AtExitHook {