Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754827AbaDVA6m (ORCPT ); Mon, 21 Apr 2014 20:58:42 -0400 Received: from mail-pd0-f180.google.com ([209.85.192.180]:64243 "EHLO mail-pd0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753252AbaDVA6j (ORCPT ); Mon, 21 Apr 2014 20:58:39 -0400 Message-ID: <5355BEBA.8040001@gmail.com> Date: Tue, 22 Apr 2014 08:58:34 +0800 From: Chen Gang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: "Rafael J. Wysocki" , Pavel Machek CC: Guan Xuetao , len.brown@intel.com, "linux-pm@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] kernel/power/hibernate.c: be sure of 'start' is not bigger than 'stop' References: <53551FCB.3030109@gmail.com> <20140421200930.GA9880@amd.pavel.ucw.cz> <1597133.Gff7RjtQZQ@vostro.rjw.lan> In-Reply-To: <1597133.Gff7RjtQZQ@vostro.rjw.lan> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/22/2014 04:43 AM, Rafael J. Wysocki wrote: > On Monday, April 21, 2014 10:09:30 PM Pavel Machek wrote: >> On Mon 2014-04-21 21:40:27, 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. >>> >>> 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 >>> >>> Signed-off-by: Chen Gang >> >>> { >>> - s64 elapsed_centisecs64; >>> + u64 elapsed_centisecs64; >>> int centisecs; >>> int k; >>> int kps; >>> >>> elapsed_centisecs64 = timeval_to_ns(stop) - timeval_to_ns(start); >>> + if ((s64)elapsed_centisecs64 < 0) { >>> + printk(KERN_ERR "PM: stop: %llu < start %llu\n", >>> + timeval_to_ns(stop), timeval_to_ns(start)); >>> + return; >>> + } >>> do_div(elapsed_centisecs64, NSEC_PER_SEC / 100); >>> centisecs = elapsed_centisecs64; >>> if (centisecs == 0) >> >> Quite a lot of code to shut up warning in mostly debugging >> function... is there alternative method of shutting it up? Have you >> seen < 0 values in wild? > > No, I don't think so. This is a purely theoretical problem that never > happens in practice, because all of the callers do the right thing. > > Rafael > OK, it sounds fine to me, I shall send patch v2 for it. Thanks. -- Chen Gang Open, share, and attitude like air, water, and life which God blessed -- 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/