[aot] Fix a deadlock in init_plt () by calling create_trampoline () o…

…utside the lock.

Fixes mono#15330.

mono/mini/aot-runtime.c

@@ -4263,10 +4263,10 @@ load_method (MonoDomain *domain, MonoAotModule *amodule, MonoImage *image, MonoM
 		}
 	}
 
-	amodule_lock (amodule);
-
 	init_plt (amodule);
 
+	amodule_lock (amodule);
+
 	mono_atomic_inc_i32 (&mono_jit_stats.methods_aot);
 
 	if (method && method->wrapper_type)
@@ -5155,7 +5155,6 @@ mono_aot_plt_resolve (gpointer aot_module, guint32 plt_info_offset, guint8 *code
  *
  *   Initialize the PLT table of the AOT module. Called lazily when the first AOT
  * method in the module is loaded to avoid committing memory by writing to it.
- * LOCKING: Assumes the AMODULE lock is held.
  */
 static void
 init_plt (MonoAotModule *amodule)
@@ -5166,23 +5165,34 @@ init_plt (MonoAotModule *amodule)
 	if (amodule->plt_inited)
 		return;
 
+	tramp = mono_create_specific_trampoline (amodule, MONO_TRAMPOLINE_AOT_PLT, mono_get_root_domain (), NULL);
+	tramp = mono_create_ftnptr (mono_domain_get (), tramp);
+
+	amodule_lock (amodule);
+
+	if (amodule->plt_inited) {
+		amodule_unlock (amodule);
+		return;
+	}
+
 	if (amodule->info.plt_size <= 1) {
 		amodule->plt_inited = TRUE;
+		amodule_unlock (amodule);
 		return;
 	}
 
-	tramp = mono_create_specific_trampoline (amodule, MONO_TRAMPOLINE_AOT_PLT, mono_get_root_domain (), NULL);
-
 	/*
 	 * Initialize the PLT entries in the GOT to point to the default targets.
 	 */
+	for (i = 1; i < amodule->info.plt_size; ++i)
+		/* All the default entries point to the AOT trampoline */
+		((gpointer*)amodule->got)[amodule->info.plt_got_offset_base + i] = tramp;
 
-	tramp = mono_create_ftnptr (mono_domain_get (), tramp);
-	 for (i = 1; i < amodule->info.plt_size; ++i)
-		 /* All the default entries point to the AOT trampoline */
-		 ((gpointer*)amodule->got)[amodule->info.plt_got_offset_base + i] = tramp;
+	mono_memory_barrier ();
 
 	amodule->plt_inited = TRUE;
+
+	amodule_unlock (amodule);
 }
 
 /*