1 files changed, 12 insertions, 1 deletions
diff --git a/vm_core.h b/vm_core.h
index 7ac6bb1ceb..5a97d10edd 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -396,6 +396,8 @@ struct rb_unblock_callback {
     void *arg;
 };
 
+struct rb_mutex_struct;
+
 struct rb_thread_struct
 {
     VALUE self;
@@ -443,7 +445,7 @@ struct rb_thread_struct
     rb_thread_lock_t interrupt_lock;
     struct rb_unblock_callback unblock;
     VALUE locking_mutex;
-    VALUE keeping_mutexes;
+    struct rb_mutex_struct *keeping_mutexes;
     int transition_for_lock;
 
     struct rb_vm_tag *tag;
@@ -496,6 +498,15 @@ struct rb_thread_struct
     int abort_on_exception;
 };
 
+struct rb_mutex_struct
+{
+    rb_thread_lock_t lock;
+    rb_thread_cond_t cond;
+    struct rb_thread_struct volatile *th;
+    volatile int cond_waiting, cond_notified;
+    struct rb_mutex_struct *next_mutex;
+};
+
 /* iseq.c */
 VALUE rb_iseq_new(NODE*, VALUE, VALUE, VALUE, VALUE);
 VALUE rb_iseq_new_with_bopt(NODE*, VALUE, VALUE, VALUE, VALUE, VALUE);