ObjectSpace.{dump,dump_all,dump_shapes} needs vm barrier. (ruby#15569)

This allows these methods to be called from ractors.

Add new exported function `rb_vm_lock_with_barrier()` that requires
users to include "vm_sync.h"

Author: luke-gruber

ext/objspace/objspace_dump.c

@@ -29,7 +29,7 @@
 #include "ruby/util.h"
 #include "ruby/io.h"
 #include "vm_callinfo.h"
-#include "vm_core.h"
+#include "vm_sync.h"
 
 RUBY_EXTERN const char ruby_hexdigits[];
 
@@ -771,22 +771,33 @@ dump_result(struct dump_config *dc)
     return dc->given_output;
 }
 
-/* :nodoc: */
 static VALUE
-objspace_dump(VALUE os, VALUE obj, VALUE output)
+dump_locked(void *args_p)
 {
     struct dump_config dc = {0,};
+    VALUE obj = ((VALUE*)args_p)[0];
+    VALUE output = ((VALUE*)args_p)[1];
+
     if (!RB_SPECIAL_CONST_P(obj)) {
         dc.cur_page_slot_size = rb_gc_obj_slot_size(obj);
     }
-
     dump_output(&dc, output, Qnil, Qnil, Qnil);
 
     dump_object(obj, &dc);
 
     return dump_result(&dc);
 }
 
+/* :nodoc: */
+static VALUE
+objspace_dump(VALUE os, VALUE obj, VALUE output)
+{
+    VALUE args[2];
+    args[0] = obj;
+    args[1] = output;
+    return rb_vm_lock_with_barrier(dump_locked, (void*)args);
+}
+
 static void
 shape_id_i(shape_id_t shape_id, void *data)
 {
@@ -835,11 +846,15 @@ shape_id_i(shape_id_t shape_id, void *data)
     dump_append(dc, "}\n");
 }
 
-/* :nodoc: */
 static VALUE
-objspace_dump_all(VALUE os, VALUE output, VALUE full, VALUE since, VALUE shapes)
+dump_all_locked(void *args_p)
 {
     struct dump_config dc = {0,};
+    VALUE output = ((VALUE*)args_p)[0];
+    VALUE full = ((VALUE*)args_p)[1];
+    VALUE since = ((VALUE*)args_p)[2];
+    VALUE shapes = ((VALUE*)args_p)[3];
+
     dump_output(&dc, output, full, since, shapes);
 
     if (!dc.partial_dump || dc.since == 0) {
@@ -860,9 +875,23 @@ objspace_dump_all(VALUE os, VALUE output, VALUE full, VALUE since, VALUE shapes)
 
 /* :nodoc: */
 static VALUE
-objspace_dump_shapes(VALUE os, VALUE output, VALUE shapes)
+objspace_dump_all(VALUE os, VALUE output, VALUE full, VALUE since, VALUE shapes)
+{
+    VALUE args[4];
+    args[0] = output;
+    args[1] = full;
+    args[2] = since;
+    args[3] = shapes;
+    return rb_vm_lock_with_barrier(dump_all_locked, (void*)args);
+}
+
+static VALUE
+dump_shapes_locked(void *args_p)
 {
     struct dump_config dc = {0,};
+    VALUE output = ((VALUE*)args_p)[0];
+    VALUE shapes = ((VALUE*)args_p)[1];
+
     dump_output(&dc, output, Qfalse, Qnil, shapes);
 
     if (RTEST(shapes)) {
@@ -871,13 +900,26 @@ objspace_dump_shapes(VALUE os, VALUE output, VALUE shapes)
     return dump_result(&dc);
 }
 
+/* :nodoc: */
+static VALUE
+objspace_dump_shapes(VALUE os, VALUE output, VALUE shapes)
+{
+    VALUE args[2];
+    args[0] = output;
+    args[1] = shapes;
+    return rb_vm_lock_with_barrier(dump_shapes_locked, (void*)args);
+}
+
 void
 Init_objspace_dump(VALUE rb_mObjSpace)
 {
 #undef rb_intern
 #if 0
     rb_mObjSpace = rb_define_module("ObjectSpace"); /* let rdoc know */
 #endif
+#ifdef HAVE_RB_EXT_RACTOR_SAFE
+    RB_EXT_RACTOR_SAFE(true);
+#endif
 
     rb_define_module_function(rb_mObjSpace, "_dump", objspace_dump, 2);
     rb_define_module_function(rb_mObjSpace, "_dump_all", objspace_dump_all, 4);

test/objspace/test_objspace.rb

@@ -827,6 +827,27 @@ def dump_my_heap_please
     end
   end
 
+  def test_dump_all_with_ractors
+    assert_ractor("#{<<-"begin;"}#{<<-'end;'}")
+    begin;
+      require "objspace"
+      require "tempfile"
+      require "json"
+      rs = 4.times.map do
+        Ractor.new do
+          Tempfile.create do |f|
+            ObjectSpace.dump_all(output: f)
+            f.close
+            File.readlines(f.path).each do |line|
+              JSON.parse(line)
+            end
+          end
+        end
+      end
+      rs.each(&:join)
+    end;
+  end
+
   def test_dump_uninitialized_file
     assert_in_out_err(%[-robjspace], <<-RUBY) do |(output), (error)|
       puts ObjectSpace.dump(File.allocate)

vm_sync.c

@@ -297,3 +297,14 @@ rb_ec_vm_lock_rec_release(const rb_execution_context_t *ec,
 
     VM_ASSERT(recorded_lock_rec == rb_ec_vm_lock_rec(ec));
 }
+
+VALUE
+rb_vm_lock_with_barrier(VALUE (*func)(void *args), void *args)
+{
+    VALUE result = 0;
+    RB_VM_LOCKING() {
+        rb_vm_barrier();
+        result = func(args);
+    }
+    return result;
+}

vm_sync.h

@@ -28,6 +28,10 @@ void rb_vm_lock_leave_body_nb(unsigned int *lev APPEND_LOCATION_ARGS);
 void rb_vm_lock_leave_body(unsigned int *lev APPEND_LOCATION_ARGS);
 void rb_vm_barrier(void);
 
+RUBY_SYMBOL_EXPORT_BEGIN
+VALUE rb_vm_lock_with_barrier(VALUE (*func)(void *args), void *args);
+RUBY_SYMBOL_EXPORT_END
+
 #if RUBY_DEBUG
 // GET_VM()
 #include "vm_core.h"