From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BBA5518DF6E for ; Wed, 16 Oct 2024 18:20:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729102813; cv=none; b=OnVWtD95VQT5LkWO4lPyDZzSx8z6ski6GFtkK0n0/DIPxbxukkmylUjdQepOjXCGizJazw/6TIDPpCoA0WtKLOg/ymE5QYqMDsJYg2YiWY4G/wS5ssoxWoQkht98XAoBNgJBwns2aJlfYlvPP/LxmFfbyjKmG+dOi+YBRj/qhuc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729102813; c=relaxed/simple; bh=asShdv9v8uS093w6wQHmJM/MPm08b8CD1idDYHcSA9M=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=NfFe/rzyhhySXouynFyHf24LO7hlTjtuS8zGQQXmDDz787ryLNVdTS0cxs+PsMe9IcmyDePOVy+9Fwk0jA3ZmvwZZgbFLcFaZN230O/rD4GQQO8EH8rbOOAoeAZvk+hcjbzviDrtIbphKZa/5HqHo8l2oyhfzPD5P7BP2l3clx8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=eChrfsz8; arc=none smtp.client-ip=192.198.163.18 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="eChrfsz8" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1729102812; x=1760638812; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=asShdv9v8uS093w6wQHmJM/MPm08b8CD1idDYHcSA9M=; b=eChrfsz8g0W1iT0TFspMdvGCQwLbxJoPDaS1jJzwbI7BMVM4euxM6YVn QXQ3lcZ8oYZzS9zw1vNpYDymsvlcQhJgX8PJqqrJQ1HuaO22cWi2T3sNK wHmi7gcfkoNBJAvKcPXgPj4/HXUJQif4E5DIW3DnlzMr5cwFbtVBa35+Y dX9PWqcxPE3zqonNbpSY9370zUm/Bx3l/iiXPi5QfKsd5cWiUdvhjzF7Y O0kriNxcHdQpQlv2Mb+7MSDPRbplICzuqUB9aRAmxH1lfhTna8BkPRJa3 eNSEPGoHEF25r7ROot0A5f0cfOowcG8pR5X0b5OVFtBoJYvZYdrGJMmPq A==; X-CSE-ConnectionGUID: 8gr6tdvSR/icpHPHM4IhsQ== X-CSE-MsgGUID: FQiFknhTS6eUmFIOxyF1Vg== X-IronPort-AV: E=McAfee;i="6700,10204,11226"; a="28008343" X-IronPort-AV: E=Sophos;i="6.11,208,1725346800"; d="scan'208";a="28008343" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa112.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Oct 2024 11:20:11 -0700 X-CSE-ConnectionGUID: 3niBpy1/R624DLq2Gby+eQ== X-CSE-MsgGUID: GgC6IEmPTQi7O/UgQS9nvw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.11,208,1725346800"; d="scan'208";a="78341263" Received: from smile.fi.intel.com ([10.237.72.154]) by fmviesa008.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Oct 2024 11:20:07 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.98) (envelope-from ) id 1t18cu-00000003ruF-02Dx; Wed, 16 Oct 2024 21:20:04 +0300 Date: Wed, 16 Oct 2024 21:20:03 +0300 From: Andy Shevchenko To: Dave Hansen Cc: Ingo Molnar , Uros Bizjak , linux-mm@kvack.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Dennis Zhou , Tejun Heo , Christoph Lameter , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt Subject: Re: [PATCH v1 1/1] x86/percpu: Cast -1 to argument type when comparing in percpu_add_op() Message-ID: References: <20240905170356.260300-1-andriy.shevchenko@linux.intel.com> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: 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 On Wed, Oct 16, 2024 at 09:06:13PM +0300, Andy Shevchenko wrote: > On Wed, Oct 16, 2024 at 08:44:56AM -0700, Dave Hansen wrote: ... > > This doesn't _look_ right. See below. ... > Maybe more readable, but wouldn't it be theoretically buggy for u64? > I'm talking about the case when u64 == UINT_MAX, which will be true > in your case and false in mine. > > > const int pao_ID__ = (__builtin_constant_p(val) && > > ((val) == 1 || (int)(val) == -1)) ? > > > > (int)(val) : 0; This code _is_ buggy, thanks to my new test case. [ 66.161375] pcp -1 (0xffffffffffffffff) != expected 4294967295 (0xffffffff) Hence, I'll send a v2 with the test case and updated Subject. -- With Best Regards, Andy Shevchenko