From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752145AbaEFVwU (ORCPT ); Tue, 6 May 2014 17:52:20 -0400 Received: from mail-wi0-f174.google.com ([209.85.212.174]:63415 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751110AbaEFVwT convert rfc822-to-8bit (ORCPT ); Tue, 6 May 2014 17:52:19 -0400 Subject: Re: [PATCH 6/6] mm: Postpone the disabling of kmemleak early logging Mime-Version: 1.0 (Mac OS X Mail 7.2 \(1874\)) Content-Type: text/plain; charset=windows-1252 From: Catalin Marinas In-Reply-To: <536926DD.30402@oracle.com> Date: Tue, 6 May 2014 22:52:16 +0100 Cc: "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Andrew Morton , Li Zefan Content-Transfer-Encoding: 8BIT Message-Id: <49655FE2-17CA-433C-8F4A-76DD6C2FEF61@arm.com> References: <1399038070-1540-1-git-send-email-catalin.marinas@arm.com> <1399038070-1540-7-git-send-email-catalin.marinas@arm.com> <5368FDBB.8070106@oracle.com> <20140506170549.GM23957@arm.com> <536926DD.30402@oracle.com> To: Sasha Levin X-Mailer: Apple Mail (2.1874) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6 May 2014, at 19:15, Sasha Levin wrote: > On 05/06/2014 01:05 PM, Catalin Marinas wrote: >> On Tue, May 06, 2014 at 04:20:27PM +0100, Sasha Levin wrote: >>> On 05/02/2014 09:41 AM, Catalin Marinas wrote: >>>> Currently, kmemleak_early_log is disabled at the beginning of the >>>> kmemleak_init() function, before the full kmemleak tracing is actually >>>> enabled. In this small window, kmem_cache_create() is called by kmemleak >>>> which triggers additional memory allocation that are not traced. This >>>> patch moves the kmemleak_early_log disabling further down and at the >>>> same time with full kmemleak enabling. >>>> >>>> Signed-off-by: Catalin Marinas >>>> Cc: Andrew Morton >>> >>> This patch makes the kernel die during the boot process: >>> >>> [ 24.471801] BUG: unable to handle kernel paging request at ffffffff922f2b93 >>> [ 24.472496] IP: [] log_early+0x0/0xcd >> >> Thanks for reporting this. I assume you run with >> CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF enabled and kmemleak_early_log remains >> set even though kmemleak is not in use. >> >> Does the patch below fix it? > > Nope, that didn't help as I don't have DEBUG_KMEMLEAK_DEFAULT_OFF enabled. > > For reference: > > $ cat .config | grep KMEMLEAK > CONFIG_HAVE_DEBUG_KMEMLEAK=y > CONFIG_DEBUG_KMEMLEAK=y > CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE=400 > # CONFIG_DEBUG_KMEMLEAK_TEST is not set > # CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF is not set I assume your dmesg shows some kmemleak error during boot? I’ll send another patch tomorrow. The code around kmemleak_init was changed by commit 8910ae896c8c (kmemleak: change some global variables to int). It looks like it wasn’t just a simple conversion but slightly changed the kmemleak_early_log logic which led to false positives for the kmemleak cache objects and that’s what my patch was trying to solve. The failure is caused by kmemleak_alloc() still calling log_early() much later after the __init section has been freed because kmemleak_early_log hasn’t been set to 0 (the default off is one path, another is the kmemleak_error path). Catalin