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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 9F0DAC34047 for ; Tue, 18 Feb 2020 19:25:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7798B21D56 for ; Tue, 18 Feb 2020 19:25:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="LInPmrzn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726352AbgBRTZ2 (ORCPT ); Tue, 18 Feb 2020 14:25:28 -0500 Received: from mail-ot1-f68.google.com ([209.85.210.68]:39472 "EHLO mail-ot1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726291AbgBRTZ2 (ORCPT ); Tue, 18 Feb 2020 14:25:28 -0500 Received: by mail-ot1-f68.google.com with SMTP id 77so20651704oty.6 for ; Tue, 18 Feb 2020 11:25:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=ckyuMsvFFux27LQS5gOMapLWD0YEn71aKg1bpT/CAjA=; b=LInPmrzntLI+jey3b9w6N4OrF2TdfG25R+K2QF/mwg6GTKX2jDpNjmqDrf8XptazpF 0eJnz6Q1Nly0gjKtPY5OS3iUmwv2lWV1k8wAwe2ozY+oI5mVBxRPMXXZihTZQor5kX0u 3Z77DqUqb83Gcv5APxzKjWL+9YImg9aDivBa0Yw8wOsd48e1PeNJhVnQoYPq+5fWyPQ7 UY64+pNkMncc7yibup3yOtrxNd1WCEAXPZPTFTY3lPqdM23ARdrIdLB7gIW137/Ml04T QIo328ZrSU7GsXA8u/PQQuXj4f+n8xkH3xf7jSC/xzzDjs/3KufJnszHAFlIni42hjyI z/8g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=ckyuMsvFFux27LQS5gOMapLWD0YEn71aKg1bpT/CAjA=; b=cWIl+DTgl9V97RtZdP+zz8R6PP+CrP4a6U4tkzL8J9gbLDSnwLwkpAR8FSyXRbtuYn ovwmR1qYAy2gz05TA1JEkgx9BQKvme6DdpkVsUsQ488tNBYRLoF+hqqW7Xkud8ghtyWk XhfPoCTsrX9NYac+RWjvGGR0vs8hhiGJYW37xj7w/v/XJVjlqBVYaKaaFJf64Mck2Fm/ pyIz0f6/aXyDHZVKbKoAUuitIUne1EHBpprUhcUobpBvn/v+daRDMls6LMvgfq1WjKQu /GQorPZrvjbW4LiLqRFbYSpgi6Xt3Yj3zJpwemqV1/SqFFoOuRyKXLuPwRRylNoqyPVa ux/Q== X-Gm-Message-State: APjAAAW8lBAeXf5O1SA+pPnEsuE3iRBEJlSOup9BonX8qcDQI2hr12cP jc/25/XZNWeUuCc390CswES9a7TX9z0HKRMugsSHww== X-Google-Smtp-Source: APXvYqxdPz6sqyLtEpkrPTZBYVznrMujoqBsbH5oFjCkK58IwNmBJxEu5A/RAN57n0ppJXZezlJKQabZ5mLB3Rudsc4= X-Received: by 2002:a9d:6a2:: with SMTP id 31mr16569798otx.313.1582053925869; Tue, 18 Feb 2020 11:25:25 -0800 (PST) MIME-Version: 1.0 References: <20200211213128.73302-1-almasrymina@google.com> <20200211151906.637d1703e4756066583b89da@linux-foundation.org> <1582035660.7365.90.camel@lca.pw> In-Reply-To: From: Mina Almasry Date: Tue, 18 Feb 2020 11:25:14 -0800 Message-ID: Subject: Re: [PATCH v12 1/9] hugetlb_cgroup: Add hugetlb_cgroup reservation counter To: Mike Kravetz Cc: Qian Cai , Andrew Morton , shuah , David Rientjes , Shakeel Butt , Greg Thelen , open list , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, cgroups@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Tue, Feb 18, 2020 at 11:14 AM Mike Kravetz wrote: > > On 2/18/20 10:35 AM, Mina Almasry wrote: > > On Tue, Feb 18, 2020 at 6:21 AM Qian Cai wrote: > >> > >> On Tue, 2020-02-11 at 15:19 -0800, Andrew Morton wrote: > >>> On Tue, 11 Feb 2020 13:31:20 -0800 Mina Almasry wrote: > >>> > >> [ 7933.806377][T14355] ------------[ cut here ]------------ > >> [ 7933.806541][T14355] kernel BUG at mm/hugetlb.c:490! > >> VM_BUG_ON(t - f <= 1); > >> [ 7933.806562][T14355] Oops: Exception in kernel mode, sig: 5 [#1] > > > Hi Qian, > > > > Yes this VM_BUG_ON was added by a patch in the series ("hugetlb: > > disable region_add file_region coalescing") so it's definitely related > > to the series. I'm taking a look at why this VM_BUG_ON fires. Can you > > confirm you reproduce this by running hugemmap06 from the ltp on a > > powerpc machine? Can I maybe have your config? > > > > Thanks! > > Hi Mina, > > Looking at the region_chg code again, we do a > > resv->adds_in_progress += *out_regions_needed; > > and then potentially drop the lock to allocate the needed entries. Could > anopther thread (only adding reservation for a single page) then come in > and notice that there are not enough entries in the cache and hit the > VM_BUG_ON()? Maybe. Also I'm thinking the code thinks actual_regions_needed >= in_regions_needed, but that doesn't seem like a guarantee. I think this call sequence with the same t->f range would violate that: region_chg (regions_needed=1) region_chg (regions_needed=1) region_add (fills in the range) region_add (in_regions_needed = 1, actual_regions_needed = 0, so assumptions in the code break). Luckily it seems the ltp readily reproduces this, so I'm working on reproducing it. I should have a fix soon, at least if I can reproduce it as well.