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=-3.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 ACCA9C65BAE for ; Thu, 13 Dec 2018 19:43:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 816E02086D for ; Thu, 13 Dec 2018 19:43:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 816E02086D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729033AbeLMTns (ORCPT ); Thu, 13 Dec 2018 14:43:48 -0500 Received: from mx2.suse.de ([195.135.220.15]:44610 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728626AbeLMTno (ORCPT ); Thu, 13 Dec 2018 14:43:44 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id B6EDCACE8; Thu, 13 Dec 2018 19:43:42 +0000 (UTC) Subject: Re: [PATCH] mm: Replace verify_mm_writelocked() by lockdep_assert_held_exclusive() To: Waiman Long , Andrew Morton , Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Yang Shi References: <1544729885-30702-1-git-send-email-longman@redhat.com> From: Vlastimil Babka Openpgp: preference=signencrypt Message-ID: Date: Thu, 13 Dec 2018 20:40:44 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.3 MIME-Version: 1.0 In-Reply-To: <1544729885-30702-1-git-send-email-longman@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/13/18 8:38 PM, Waiman Long wrote: > Using down_read_trylock() to check if a task holds a write lock on > a rwsem is not reliable. A task can hold a read lock on a rwsem and > down_read_trylock() can fail if a writer is waiting in the wait queue. > > So use lockdep_assert_held_exclusive() instead which can do the right > check when CONFIG_LOCKDEP is on. > > Signed-off-by: Waiman Long There's already a patch in mmotm removing this completely: https://www.ozlabs.org/~akpm/mmots/broken-out/mm-mmap-remove-verify_mm_writelocked.patch Vlastimil