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=-6.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,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 CE480C65BAE for ; Thu, 13 Dec 2018 22:04:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9C10C20870 for ; Thu, 13 Dec 2018 22:04:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9C10C20870 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.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 S1728537AbeLMWEQ (ORCPT ); Thu, 13 Dec 2018 17:04:16 -0500 Received: from mx1.redhat.com ([209.132.183.28]:3934 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726435AbeLMWEP (ORCPT ); Thu, 13 Dec 2018 17:04:15 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5730F3002892; Thu, 13 Dec 2018 22:04:15 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-223.bos.redhat.com [10.18.17.223]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4A8AD67649; Thu, 13 Dec 2018 22:04:14 +0000 (UTC) Subject: Re: [PATCH 2/2] debugobjects: Print warnings outside bucket lock To: Dmitry Safonov , linux-kernel@vger.kernel.org Cc: 0x7f454c46@gmail.com, kernel test robot , Andrew Morton , Ingo Molnar , Peter Zijlstra , Sergey Senozhatsky , Thomas Gleixner References: <20181213043447.23006-1-dima@arista.com> <20181213043447.23006-2-dima@arista.com> From: Waiman Long Openpgp: preference=signencrypt Autocrypt: addr=longman@redhat.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181213043447.23006-2-dima@arista.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Thu, 13 Dec 2018 22:04:15 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/12/2018 11:34 PM, Dmitry Safonov wrote: > Whenever debugobjects finds invalid pattern during life time of a kernel > object such as: > - Activation of uninitialized objects > - Initialization of active objects > - Usage of freed/destroyed objects > it prints a warning and tries to make fixup over an object. > > Unfortunately, it becomes error-prone to use WARN() or printing under > debugobjects bucket lock: printk() may defer work to workqueue, and > realization of workqueues uses debugobjects. Further, console drivers > use page allocator, potentially vmalloc() or slub/slab. Which reasonably > makes lockdep to go nuts as there are debug_check_no_obj_freed() checks > in allocators. > > Move printings out of debugobjets bucket lock to address the potential > lockups. > > Link: lkml.kernel.org/r/20181211091154.GL23332@shao2-debian > Reported-by: kernel test robot > Cc: Andrew Morton > Cc: Ingo Molnar > Cc: Peter Zijlstra > Cc: Sergey Senozhatsky > Cc: Thomas Gleixner > Cc: Waiman Long > Signed-off-by: Dmitry Safonov > --- > lib/debugobjects.c | 89 ++++++++++++++++++++++++---------------------- > 1 file changed, 47 insertions(+), 42 deletions(-) > > diff --git a/lib/debugobjects.c b/lib/debugobjects.c > index 98968219405b..0c92e46cb588 100644 > --- a/lib/debugobjects.c > +++ b/lib/debugobjects.c > @@ -313,7 +313,7 @@ static struct debug_bucket *get_bucket(unsigned long addr) > return &obj_hash[hash]; > } > > -static void debug_print_object(struct debug_obj *obj, char *msg) > +static void __debug_print_object(struct debug_obj *obj, char *msg) > { > struct debug_obj_descr *descr = obj->descr; > static int limit; > @@ -330,6 +330,14 @@ static void debug_print_object(struct debug_obj *obj, char *msg) > debug_objects_warnings++; > } > > +#define debug_print_object(obj, msg, lock, flags) \ > + do { \ > + struct debug_obj tmp = *obj; \ > + \ > + raw_spin_unlock_irqrestore(lock, flags); \ > + __debug_print_object(&tmp, msg); \ > + } while(0) > + My main problem with this patch is the hiding of the unlock call in the macro. I will prefer matching unlocks to be clearly visible in the function bodies. Otherwise, the readers may be confused. Cheers, Longman