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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 2785BC43441 for ; Tue, 27 Nov 2018 15:52:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E09FB2086B for ; Tue, 27 Nov 2018 15:52:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E09FB2086B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com 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 S1730254AbeK1Cud (ORCPT ); Tue, 27 Nov 2018 21:50:33 -0500 Received: from mga11.intel.com ([192.55.52.93]:56624 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729553AbeK1Cud (ORCPT ); Tue, 27 Nov 2018 21:50:33 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Nov 2018 07:52:13 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,287,1539673200"; d="scan'208";a="93733830" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.154]) by fmsmga008.fm.intel.com with ESMTP; 27 Nov 2018 07:52:13 -0800 Date: Tue, 27 Nov 2018 07:52:13 -0800 From: Sean Christopherson To: Heiko Carstens Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, linux-mm@kvack.org, "Kirill A . Shutemov" , Martin Schwidefsky Subject: Re: [PATCH] mm: warn only once if page table misaccounting is detected Message-ID: <20181127155213.GB27075@linux.intel.com> References: <20181127083603.39041-1-heiko.carstens@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181127083603.39041-1-heiko.carstens@de.ibm.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 27, 2018 at 09:36:03AM +0100, Heiko Carstens wrote: > Use pr_alert_once() instead of pr_alert() if page table misaccounting > has been detected. > > If this happens once it is very likely that there will be numerous > other occurrence as well, which would flood dmesg and the console with > hardly any added information. Therefore print the warning only once. > > Cc: Kirill A. Shutemov > Cc: Martin Schwidefsky > Signed-off-by: Heiko Carstens > --- > kernel/fork.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index 07cddff89c7b..c887e9eba89f 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -647,8 +647,8 @@ static void check_mm(struct mm_struct *mm) > } > > if (mm_pgtables_bytes(mm)) > - pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", > - mm_pgtables_bytes(mm)); > + pr_alert_once("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", > + mm_pgtables_bytes(mm)); I found the print-always behavior to be useful when developing a driver that mucked with PTEs directly via vmf_insert_pfn() and had issues with racing against exit_mmap(). It was nice to be able to recompile only the driver and rely on dmesg to let me know when I messed up yet again. Would pr_alert_ratelimited() suffice? > #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS > VM_BUG_ON_MM(mm->pmd_huge_pte, mm); > -- > 2.16.4 >