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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 CEDBEC5DF60 for ; Fri, 8 Nov 2019 09:31:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9DB72214DA for ; Fri, 8 Nov 2019 09:31:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="O84mdoRO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731030AbfKHJbn (ORCPT ); Fri, 8 Nov 2019 04:31:43 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:33128 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729873AbfKHJbn (ORCPT ); Fri, 8 Nov 2019 04:31:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=mmNnULM/VKjYavmcObobx5Rd93KoR1x/7NkcWKtN1+Q=; b=O84mdoRO2yNi9tsZBrBodcX/E 5E6ZDTyfmxhjwCMaOtvdi7eVL6nxVo1Vp3n1GDN1wcodPVMDAiGcI3RrRfZZPVALovO7AIeileEyM vm4d2KnKmPxLcLntBWldGGcFygj2lSnLIBhCZoz0vd2r7vafR3xcvApdGB+pt9RrYIFE4jSy1be03 msmvyZo5AoBNNcDNljebfvRPWa/CKJ9nqoJqtZQFMr8S/ePgYqkJAUxRR6ugOQz0dhtaxtnM2G2HA eC3I+m5SUMy0YsNdf79D5WITW7wDa6RSuoPRhliCB7A5JpCuzKVcAZFS2uY9AlNSK8fUHHsNloW6A sDoPV4Xng==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iT0cF-00018T-KV; Fri, 08 Nov 2019 09:31:39 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 67F77301A79; Fri, 8 Nov 2019 10:30:31 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 136362022B9E1; Fri, 8 Nov 2019 10:31:36 +0100 (CET) Date: Fri, 8 Nov 2019 10:31:36 +0100 From: Peter Zijlstra To: tim Cc: Johannes Weiner , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH] psi:fix divide by zero in psi_update_stats Message-ID: <20191108093136.GI4114@hirez.programming.kicks-ass.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 08, 2019 at 03:33:24PM +0800, tim wrote: > In psi_update_stats, it is possible that period has value like > 0xXXXXXXXX00000000 where the lower 32 bit is 0, then it calls div_u64 which How can this happen? Is that a valid case or should we be avoiding that?