openat(2) also performs a path lookup, so it is also subject
to pathological slowdowns like opendir(3) and open(2) syscalls.
dir.c (struct opendir_at_arg): new struct for callback
(with_gvl_gc_for_fd): new callback for rb_thread_call_with_gvl
(gc_for_fd_with_gvl): moved up
(nogvl_opendir_at): extracted from do_opendir
(opendir_at): new wrapper to release GVL for opendir_at
(do_opendir): use new wrappers to release GVL
(nogvl_dir_empty_p): adjust for gc_for_fd_with_gvl
dir.c: openat calls release GVL, too
openat(2) also performs a path lookup, so it is also subject
to pathological slowdowns like opendir(3) and open(2) syscalls.
(with_gvl_gc_for_fd): new callback for rb_thread_call_with_gvl
(gc_for_fd_with_gvl): moved up
(nogvl_opendir_at): extracted from do_opendir
(opendir_at): new wrapper to release GVL for opendir_at
(do_opendir): use new wrappers to release GVL
(nogvl_dir_empty_p): adjust for gc_for_fd_with_gvl
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60831 b2dd03c8-39d4-4d8f-98ff-823fe69b080e