io.c: fix race between read and close

* io.c (io_fillbuf): fix race between read and close, in the case
  the IO gets closed before the reading thread achieve the lock.
  [ruby-core:78845] [Bug #13076]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57199 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

io.c

@@ -1775,6 +1775,7 @@ io_fillbuf(rb_io_t *fptr)
 		rb_syserr_fail_path(e, path);
 	    }
         }
+	if (r > 0) READ_CHECK(fptr);
         fptr->rbuf.off = 0;
         fptr->rbuf.len = (int)r; /* r should be <= rbuf_capa */
         if (r == 0)

test/ruby/test_io.rb

@@ -3366,6 +3366,36 @@ __END__
     end
   end if File::BINARY != 0
 
+  def test_race_gets_and_close
+    assert_separately([], "#{<<-"begin;"}\n#{<<-"end;"}")
+    bug13076 = '[ruby-core:78845] [Bug #13076]'
+    begin;
+      100.times do |i|
+        a = []
+        t = []
+        10.times do
+          r,w = IO.pipe
+          a << [r,w]
+          t << Thread.new do
+            begin
+              while r.gets
+              end
+            rescue IOError
+            end
+          end
+        end
+        a.each do |r,w|
+          w.puts "hoge"
+          w.close
+          r.close
+        end
+        assert_nothing_raised(IOError, bug13076) {
+          t.each(&:join)
+        }
+      end
+    end;
+  end
+
   if RUBY_ENGINE == "ruby" # implementation details
     def test_foreach_rs_conversion
       make_tempfile {|t|