Fix GCExt test with resizable threadpool

Author: vchuravy

src/gc.c

@@ -4110,7 +4110,7 @@ JL_DLLEXPORT int jl_gc_conservative_gc_support_enabled(void)
     return jl_atomic_load(&support_conservative_marking);
 }
 
-JL_DLLEXPORT jl_value_t *jl_gc_internal_obj_base_ptr(void *p)
+static inline jl_value_t *internal_obj_base_ptr(void *p)
 {
     p = (char *) p - 1;
     jl_gc_pagemeta_t *meta = page_metadata(p);
@@ -4203,6 +4203,21 @@ JL_DLLEXPORT jl_value_t *jl_gc_internal_obj_base_ptr(void *p)
     return NULL;
 }
 
+JL_DLLEXPORT jl_value_t *jl_gc_internal_obj_base_ptr(void *p)
+{
+    uint8_t restore = gc_all_tls_states == NULL;
+    if (__unlikely(restore)) {
+        gc_n_threads = jl_atomic_load_acquire(&jl_n_threads);
+        gc_all_tls_states = jl_atomic_load_relaxed(&jl_all_tls_states);
+    }
+    jl_value_t *obj = internal_obj_base_ptr(p);
+    if (__unlikely(restore)) {
+        gc_n_threads = 0;
+        gc_all_tls_states = NULL;
+    }
+    return obj;
+}
+
 JL_DLLEXPORT size_t jl_gc_max_internal_obj_size(void)
 {
     return GC_MAX_SZCLASS;