RB_VM_LOCK_ENTER_NO_BARRIER

Write barrier requires VM lock because it accesses VM global bitmap
but RB_VM_LOCK_ENTER() can invoke GC because another ractor can wait
to invoke GC and RB_VM_LOCK_ENTER() is barrier point. This means that
before protecting by a write barrier, GC can invoke.
To prevent such situation, RB_VM_LOCK_ENTER_NO_BARRIER() is introduced.
This lock primitive does not become GC barrier points.

1 files changed, 13 insertions, 0 deletions

diff --git a/vm_sync.h b/vm_sync.h
index 14b63f3017..8712e1a1ca 100644
--- a/vm_sync.h
+++ b/vm_sync.h
@@ -22,6 +22,7 @@ void rb_vm_unlock_body(LOCATION_ARGS);
 
 struct rb_ractor_struct;
 void rb_vm_lock_enter_body_cr(struct rb_ractor_struct *cr, unsigned int *lev APPEND_LOCATION_ARGS);
+void rb_vm_lock_enter_body_nb(unsigned int *lev APPEND_LOCATION_ARGS);
 void rb_vm_lock_enter_body(unsigned int *lev APPEND_LOCATION_ARGS);
 void rb_vm_lock_leave_body(unsigned int *lev APPEND_LOCATION_ARGS);
 void rb_vm_barrier(void);
@@ -72,6 +73,14 @@ rb_vm_lock_enter(unsigned int *lev, const char *file, int line)
 }
 
 static inline void
+rb_vm_lock_enter_nb(unsigned int *lev, const char *file, int line)
+{
+    if (rb_multi_ractor_p()) {
+        rb_vm_lock_enter_body_nb(lev APPEND_LOCATION_PARAMS);
+    }
+}
+
+static inline void
 rb_vm_lock_leave(unsigned int *lev, const char *file, int line)
 {
     if (rb_multi_ractor_p()) {
@@ -104,6 +113,10 @@ rb_vm_lock_leave_cr(struct rb_ractor_struct *cr, unsigned int *levp, const char
 #define RB_VM_LOCK_ENTER()  { unsigned int _lev; RB_VM_LOCK_ENTER_LEV(&_lev);
 #define RB_VM_LOCK_LEAVE()    RB_VM_LOCK_LEAVE_LEV(&_lev); }
 
+#define RB_VM_LOCK_ENTER_LEV_NB(levp) rb_vm_lock_enter_nb(levp, __FILE__, __LINE__)
+#define RB_VM_LOCK_ENTER_NO_BARRIER()  { unsigned int _lev; RB_VM_LOCK_ENTER_LEV_NB(&_lev);
+#define RB_VM_LOCK_LEAVE_NO_BARRIER()    RB_VM_LOCK_LEAVE_LEV(&_lev); }
+
 #if RUBY_DEBUG > 0
 void ASSERT_vm_locking(void);
 void ASSERT_vm_unlocking(void);