From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DDD0FC433E0 for ; Fri, 29 May 2020 18:38:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C1949206A1 for ; Fri, 29 May 2020 18:38:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728061AbgE2SiZ (ORCPT ); Fri, 29 May 2020 14:38:25 -0400 Received: from mga12.intel.com ([192.55.52.136]:53988 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726487AbgE2SiY (ORCPT ); Fri, 29 May 2020 14:38:24 -0400 IronPort-SDR: X8BN8IS12sHEUaTHIkVru7AvrhIng9yqC0gZY5HE6r3J+nnPg2dXkphjAJ3v3ABT0ZFXLOU38U MHc7JLai3Zcw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 May 2020 11:38:23 -0700 IronPort-SDR: 9+ZGDviCJ42RMi6zDwfwVcQtLGz+fnchgPlZuK7dyGWULAWk6ONd6um1NhzlmeTqRxnOpzfavc bmD8/LPhKM3g== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,449,1583222400"; d="scan'208";a="285614426" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by orsmga002.jf.intel.com with ESMTP; 29 May 2020 11:38:21 -0700 Received: from andy by smile with local (Exim 4.93) (envelope-from ) id 1jejtg-009ftl-2R; Fri, 29 May 2020 21:38:24 +0300 Date: Fri, 29 May 2020 21:38:24 +0300 From: Andy Shevchenko To: Syed Nayyar Waris Cc: kbuild test robot , Linus Walleij , Andrew Morton , kbuild-all@lists.01.org, William Breathitt Gray , Arnd Bergmann , Linux-Arch , Linux Kernel Mailing List Subject: Re: [PATCH v7 1/4] bitops: Introduce the the for_each_set_clump macro Message-ID: <20200529183824.GW1634618@smile.fi.intel.com> References: <17cb2b080b9c4c36cf84436bc5690739590acc53.1590017578.git.syednwaris@gmail.com> <202005242236.NtfLt1Ae%lkp@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 29, 2020 at 11:38:18PM +0530, Syed Nayyar Waris wrote: > On Sun, May 24, 2020 at 8:15 PM kbuild test robot wrote: ... > > 579 static inline unsigned long bitmap_get_value(const unsigned long *map, > > 580 unsigned long start, > > 581 unsigned long nbits) > > 582 { > > 583 const size_t index = BIT_WORD(start); > > 584 const unsigned long offset = start % BITS_PER_LONG; > > 585 const unsigned long ceiling = roundup(start + 1, BITS_PER_LONG); > > 586 const unsigned long space = ceiling - start; > > 587 unsigned long value_low, value_high; > > 588 > > 589 if (space >= nbits) > > > 590 return (map[index] >> offset) & GENMASK(nbits - 1, 0); > > 591 else { > > 592 value_low = map[index] & BITMAP_FIRST_WORD_MASK(start); > > 593 value_high = map[index + 1] & BITMAP_LAST_WORD_MASK(start + nbits); > > 594 return (value_low >> offset) | (value_high << space); > > 595 } > > 596 } > Regarding the above compilation warnings. All the warnings are because > of GENMASK usage in my patch. > The warnings are coming because of sanity checks present for 'GENMASK' > macro in include/linux/bits.h. > > Taking the example statement (in my patch) where compilation warning > is getting reported: > return (map[index] >> offset) & GENMASK(nbits - 1, 0); > > 'nbits' is of type 'unsigned long'. > In above, the sanity check is comparing '0' with unsigned value. And > unsigned value can't be less than '0' ever, hence the warning. > But this warning will occur whenever there will be '0' as one of the > 'argument' and an unsigned variable as another 'argument' for GENMASK. > > This warning is getting cleared if I cast the 'nbits' to 'long'. > > Let me know if I should submit a next patch with the casts applied. > What do you guys think? Proper fix is to fix GENMASK(), but allowed workaround is to use (BIT(nbits) - 1) instead. -- With Best Regards, Andy Shevchenko