Lock finalizers lists at exit (#49931)

src/gc.c

@@ -495,13 +495,18 @@ static void schedule_all_finalizers(arraylist_t *flist) JL_NOTSAFEPOINT
 
 void jl_gc_run_all_finalizers(jl_task_t *ct)
 {
+    // this is called from `jl_atexit_hook`; threads could still be running
+    // so we have to guard the finalizers' lists
+    JL_LOCK_NOGC(&finalizers_lock);
     schedule_all_finalizers(&finalizer_list_marked);
     // This could be run before we had a chance to setup all threads
     for (int i = 0;i < jl_n_threads;i++) {
         jl_ptls_t ptls2 = jl_all_tls_states[i];
         if (ptls2)
             schedule_all_finalizers(&ptls2->finalizers);
     }
+    // unlock here because `run_finalizers` locks this
+    JL_UNLOCK_NOGC(&finalizers_lock);
     run_finalizers(ct);
 }