From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx148.postini.com [74.125.245.148]) by kanga.kvack.org (Postfix) with SMTP id 3AA956B006C for ; Fri, 7 Dec 2012 21:00:55 -0500 (EST) Message-ID: <1354932053.17101.113.camel@gandalf.local.home> Subject: Re: [memcg:since-3.6 493/499] include/trace/events/filemap.h:14:1: sparse: incompatible types for operation (<) From: Steven Rostedt Date: Fri, 07 Dec 2012 21:00:53 -0500 In-Reply-To: <87ehj81pxx.fsf@free.fr> References: <50b7f3c5.kjvAZJjuJNxsqjDZ%fengguang.wu@intel.com> <87ehj81pxx.fsf@free.fr> Content-Type: text/plain; charset="ISO-8859-15" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Robert Jarzmik Cc: Frederic Weisbecker , Ingo Molnar , linux-mm@kvack.org, Andrew Morton , Michal Hocko , kbuild test robot On Sun, 2012-12-02 at 15:36 +0100, Robert Jarzmik wrote: > kbuild test robot 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 * > > 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 * > > 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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org