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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 367BAC433F5 for ; Thu, 10 Feb 2022 12:53:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241836AbiBJMxs (ORCPT ); Thu, 10 Feb 2022 07:53:48 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:36832 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236713AbiBJMxr (ORCPT ); Thu, 10 Feb 2022 07:53:47 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7166D1026; Thu, 10 Feb 2022 04:53:48 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 0ED1061DCC; Thu, 10 Feb 2022 12:53:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BCE8AC004E1; Thu, 10 Feb 2022 12:53:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1644497627; bh=Sj8DWq94LOKTBM0ypVNljY/FQe/q5/1ffqBT+QjXKsU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nqLLEdK01Ls4G9UhwGNLKFP2ED7XDuwawFhl64Aal59FMAGnTN6bg54QVqVxEp+3n vfdLYXzwTJ9C3myyptw2qrYxUB0EbyRCJL54k4nBWTIkIHJjNDXRguCeTvNJZ+BcBR rDvOeJkfp5v6S39D8dzpoPDPzklGzEIkUCmOEOzs= Date: Thu, 10 Feb 2022 13:53:43 +0100 From: Greg KH To: Cheng Jui Wang Cc: Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Boqun Feng , Matthias Brugger , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, stable@vger.kernel.org, wsd_upstream@mediatek.com, Eason-YH Lin , Kobe-CP Wu , Jeff-CC Hsu Subject: Re: [PATCH] lockdep: Correct lock_classes index mapping Message-ID: References: <20220210105011.21712-1-cheng-jui.wang@mediatek.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220210105011.21712-1-cheng-jui.wang@mediatek.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 10, 2022 at 06:50:11PM +0800, Cheng Jui Wang wrote: > A kernel exception was hit when trying to dump /proc/lockdep_chains after > lockdep report "BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!": > > Unable to handle kernel paging request at virtual address 00054005450e05c3 > ... > 00054005450e05c3] address between user and kernel address ranges > ... > pc : [0xffffffece769b3a8] string+0x50/0x10c > lr : [0xffffffece769ac88] vsnprintf+0x468/0x69c > ... > Call trace: > string+0x50/0x10c > vsnprintf+0x468/0x69c > seq_printf+0x8c/0xd8 > print_name+0x64/0xf4 > lc_show+0xb8/0x128 > seq_read_iter+0x3cc/0x5fc > proc_reg_read_iter+0xdc/0x1d4 > > The cause of the problem is the function lock_chain_get_class() will > shift lock_classes index by 1, but the index don't need to be shifted > anymore since commit 01bb6f0af992 ("locking/lockdep: Change the range of > class_idx in held_lock struct") already change the index to start from > 0. > > The lock_classes[-1] located at chain_hlocks array. When printing > lock_classes[-1] after the chain_hlocks entries are modified, the > exception happened. > > The output of lockdep_chains are incorrect due to this problem too. > > Fixes: f611e8cf98ec ("lockdep: Take read/write status in consideration when generate chainkey") > > Signed-off-by: Cheng Jui Wang > --- > kernel/locking/lockdep.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > index 4a882f83aeb9..f8a0212189ca 100644 > --- a/kernel/locking/lockdep.c > +++ b/kernel/locking/lockdep.c > @@ -3462,7 +3462,7 @@ struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i) > u16 chain_hlock = chain_hlocks[chain->base + i]; > unsigned int class_idx = chain_hlock_class_idx(chain_hlock); > > - return lock_classes + class_idx - 1; > + return lock_classes + class_idx; > } > > /* > @@ -3530,7 +3530,7 @@ static void print_chain_keys_chain(struct lock_chain *chain) > hlock_id = chain_hlocks[chain->base + i]; > chain_key = print_chain_key_iteration(hlock_id, chain_key); > > - print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id) - 1); > + print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id)); > printk("\n"); > } > } > -- > 2.18.0 > This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.