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 6C775C433FF for ; Thu, 8 Aug 2019 18:18:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3227C21743 for ; Thu, 8 Aug 2019 18:18:30 +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="DYL+FtPK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390133AbfHHSS3 (ORCPT ); Thu, 8 Aug 2019 14:18:29 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:34518 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731038AbfHHSS2 (ORCPT ); Thu, 8 Aug 2019 14:18:28 -0400 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=XHC/DXG/AsJJpTqq+/d9d6/Y4cRytjPRBDIPDxq1Cy8=; b=DYL+FtPKnBxAd1YCNMrIj6xkY eKutNn+BNnoaI3sMq4H+QMbxmgy9VXDqKFZPqganM0B80hcGGXKzySE46O3LFTkiBDmqvBZh2aOUs /iT6efBCnhCEBDnxSyaAb9xiqCJaHm1KkQO8wAY3DUZrlpXceJIRZHphT5Y2dNYWp64JvSCk1OG24 wVrehRnbwmRLcsrhP4/2LH7SO23gmhofLVJC/Txjkmyyu1SCALyZwAJ089a3NiUww5OuZL/uENZxm 9+ilgWbtvtjDr2GsbzCWKRlM+mz/Jikh65vgXwbLen0E3jqcn9WG0d9ERZsx/7DnfisQGbbP63wyt ZDBzuXLNA==; Received: from willy by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1hvmzX-0005jr-2Q; Thu, 08 Aug 2019 18:18:23 +0000 Date: Thu, 8 Aug 2019 11:18:22 -0700 From: Matthew Wilcox To: Christoph Hellwig Cc: Linus Torvalds , Andrew Morton , Thomas =?iso-8859-1?Q?Hellstr=F6m?= , Jerome Glisse , Jason Gunthorpe , Steven Price , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/3] pagewalk: use lockdep_assert_held for locking validation Message-ID: <20190808181822.GK5482@bombadil.infradead.org> References: <20190808154240.9384-1-hch@lst.de> <20190808154240.9384-4-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190808154240.9384-4-hch@lst.de> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 08, 2019 at 06:42:40PM +0300, Christoph Hellwig wrote: > Use lockdep to check for held locks instead of using home grown > asserts. > > @@ -319,7 +319,7 @@ int walk_page_range(struct mm_struct *mm, unsigned long start, > if (!walk.mm) > return -EINVAL; > > - VM_BUG_ON_MM(!rwsem_is_locked(&walk.mm->mmap_sem), walk.mm); > + lockdep_assert_held(&walk.mm->mmap_sem); It occurs to me that this is exactly the pattern that lockdep_pin_lock() was designed for. I'm pretty sure things will go badly if any callee unlocks then relocks the lock.