On Sun, 2012-12-02 at 15:36 +0100, Robert Jarzmik wrote: > kbuild test robot <fengguang.wu@xxxxxxxxx> writes: > > > tree: git://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git since-3.6 > > head: 422a0f651b5cefa1b6b3ede2e1c9e540a24a6e01 > > commit: 07b81da5f80b27543ddbe3164170c64e0941a812 [493/499] mm: trace filemap add and del > > > > > > sparse warnings: > > > > + include/trace/events/filemap.h:14:1: sparse: incompatible types for operation (<) > > include/trace/events/filemap.h:14:1: left side has type struct page *<noident> > > include/trace/events/filemap.h:14:1: right side has type int > > include/trace/events/filemap.h:45:1: sparse: incompatible types for operation (<) > > include/trace/events/filemap.h:45:1: left side has type struct page *<noident> > > include/trace/events/filemap.h:45:1: right side has type int > > Hi Steven, Frederic and Ingo, Sorry for the late reply, It's end of year and I'm getting a lot of pressure at work to get things done. > > I just drop this note to make you aware (as FTRACE maintainers) of the sparse > warning I received. > > This sparse warning will touch all submission to the FTRACE events API AFAIK. > The node of the problem : > - in include/linux/ftrace_event.h, we have : > #define is_signed_type(type) (((type)(-1)) < 0) > - this is used by kernel/trace/trace_events.c > #define __common_field(type, item) > ... > is_signed_type(type) > ... > > Here, if a trace field is a pointer (for example struct page *), we end up with > this in my case : > > static int __attribute__((no_instrument_function)) > ftrace_define_fields_mm_filemap_delete_from_page_cache(struct ftrace_event_call > *event_call) { struct ftrace_raw_mm_filemap_delete_from_page_cache field; int > ret; ret = trace_define_field(event_call, "struct page *", "page", > __builtin_offsetof(typeof(field),page), sizeof(field.page), (((struct page > *)(-1)) < 0), FILTER_OTHER); if (ret) return ret; ret = > trace_define_field(event_call, "unsigned long", "i_ino", > __builtin_offsetof(typeof(field),i_ino), sizeof(field.i_ino), (((unsigned > long)(-1)) < 0), FILTER_OTHER); if (ret) return ret; ret = > trace_define_field(event_call, "unsigned long", "index", > __builtin_offsetof(typeof(field),index), sizeof(field.index), (((unsigned > long)(-1)) < 0), FILTER_OTHER); if (ret) return ret; ret = > trace_define_field(event_call, "dev_t", "s_dev", > __builtin_offsetof(typeof(field),s_dev), sizeof(field.s_dev), (((dev_t)(-1)) < > 0), FILTER_OTHER); if (ret) return ret;; return ret; }; ;; > > And I think, (((struct page *)(-1)) < 0) gives the warning. I don't know if > "is_signed_type()" makes sense on a pointer, but I think you'll get other > reports of that kind for any new event added to trace API. Hmm, this is mostly automated via the macros. Not sure how we can differentiate a pointer from other fields. Would this be fixed if we did: #define is_signed_type(type) (((type)(-1) < (type)0) ? -- Steve -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>