Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752535AbaDVHVR (ORCPT ); Tue, 22 Apr 2014 03:21:17 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:52432 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750756AbaDVHVP (ORCPT ); Tue, 22 Apr 2014 03:21:15 -0400 Date: Tue, 22 Apr 2014 09:21:12 +0200 From: Pavel Machek To: Chen Gang Cc: "Rafael J. Wysocki" , Guan Xuetao , len.brown@intel.com, "linux-kernel@vger.kernel.org" , "linux-pm@vger.kernel.org" Subject: Re: [PATCH v2] kernel/power/hibernate.c: use 'u64' instead of 's64' to avoid warning Message-ID: <20140422072112.GB14108@amd.pavel.ucw.cz> References: <5355C5F0.6020606@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5355C5F0.6020606@gmail.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 2014-04-22 09:29:20, Chen Gang wrote: > For do_div(), it need 'u64' type, which means the outside must be sure > of 'start' is not bigger than 'stop', or it will report warning. > > Even if 'start' was really bigger than 'stop', it would print incorrect > information, but for kernel, it still can continue, so use WARN_ON() is > enough. > > The related warning (with allmodconfig for unicore32): > > CC kernel/power/hibernate.o > kernel/power/hibernate.c: In function ‘swsusp_show_speed’: > kernel/power/hibernate.c:237: warning: comparison of distinct pointer types lacks a cast > > Certainly better, but > - s64 elapsed_centisecs64; > + u64 elapsed_centisecs64; > int centisecs; > int k; > int kps; > > elapsed_centisecs64 = timeval_to_ns(stop) - timeval_to_ns(start); > + WARN_ON((s64)elapsed_centisecs64 < 0); > do_div(elapsed_centisecs64, NSEC_PER_SEC / 100); > centisecs = elapsed_centisecs64; ...do we need to do the WARN_ON()? Only result of underflow will be very long elapsed time reported... that does not sound too bad. ... and it will be quite obvious what went wrong. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/