From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-f199.google.com (mail-pl1-f199.google.com [209.85.214.199]) by kanga.kvack.org (Postfix) with ESMTP id 469606B1F22 for ; Tue, 20 Nov 2018 07:11:08 -0500 (EST) Received: by mail-pl1-f199.google.com with SMTP id h10so1249294plk.12 for ; Tue, 20 Nov 2018 04:11:08 -0800 (PST) Received: from out4437.biz.mail.alibaba.com (out4437.biz.mail.alibaba.com. [47.88.44.37]) by mx.google.com with ESMTPS id f18si13984202pgl.457.2018.11.20.04.11.05 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 20 Nov 2018 04:11:06 -0800 (PST) Subject: Re: [LKP] dd2283f260 [ 97.263072] WARNING:at_kernel/locking/lockdep.c:#lock_downgrade References: <20181115055443.GF18977@shao2-debian> <20181120085749.lj7dzk52633oq42s@kshutemo-mobl1> From: Yang Shi Message-ID: <9dec33d0-f408-8428-b004-fa63fc2e9091@linux.alibaba.com> Date: Tue, 20 Nov 2018 20:10:51 +0800 MIME-Version: 1.0 In-Reply-To: <20181120085749.lj7dzk52633oq42s@kshutemo-mobl1> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: kernel test robot , Waiman Long , Matthew Wilcox , Andrew Morton , Linux Memory Management List , linux-kernel@vger.kernel.org, LKP , Michal Hocko , Vlastimil Babka On 11/20/18 4:57 PM, Kirill A. Shutemov wrote: > On Fri, Nov 16, 2018 at 08:56:04AM -0800, Yang Shi wrote: >>> a8dda165ec vfree: add debug might_sleep() >>> dd2283f260 mm: mmap: zap pages with read mmap_sem in munmap >>> 5929a1f0ff Merge tag 'riscv-for-linus-4.20-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/palmer/riscv-linux >>> 0bc80e3cb0 Add linux-next specific files for 20181114 >>> +-----------------------------------------------------+------------+------------+------------+---------------+ >>> | | a8dda165ec | dd2283f260 | 5929a1f0ff | next-20181114 | >>> +-----------------------------------------------------+------------+------------+------------+---------------+ >>> | boot_successes | 314 | 178 | 190 | 168 | >>> | boot_failures | 393 | 27 | 21 | 40 | >>> | WARNING:held_lock_freed | 383 | 23 | 17 | 39 | >>> | is_freeing_memory#-#,with_a_lock_still_held_there | 383 | 23 | 17 | 39 | >>> | BUG:unable_to_handle_kernel | 5 | 2 | 4 | 1 | >>> | Oops:#[##] | 9 | 3 | 4 | 1 | >>> | EIP:debug_check_no_locks_freed | 9 | 3 | 4 | 1 | >>> | Kernel_panic-not_syncing:Fatal_exception | 9 | 3 | 4 | 1 | >>> | Mem-Info | 4 | 1 | | | >>> | invoked_oom-killer:gfp_mask=0x | 1 | 1 | | | >>> | WARNING:at_kernel/locking/lockdep.c:#lock_downgrade | 0 | 6 | 4 | 7 | >>> | EIP:lock_downgrade | 0 | 6 | 4 | 7 | >>> +-----------------------------------------------------+------------+------------+------------+---------------+ >>> >>> [ 96.288009] random: get_random_u32 called from arch_rnd+0x3c/0x70 with crng_init=0 >>> [ 96.359626] input_id (331) used greatest stack depth: 6360 bytes left >>> [ 96.749228] grep (358) used greatest stack depth: 6336 bytes left >>> [ 96.921470] network.sh (341) used greatest stack depth: 6212 bytes left >>> [ 97.262340] >>> [ 97.262587] ========================= >>> [ 97.263072] WARNING: held lock freed! >>> [ 97.263536] 4.19.0-06969-gdd2283f #1 Not tainted >>> [ 97.264110] ------------------------- >>> [ 97.264575] udevd/198 is freeing memory 9c16c930-9c16c99b, with a lock still held there! >>> [ 97.265542] (ptrval) (&anon_vma->rwsem){....}, at: unlink_anon_vmas+0x14e/0x420 >>> [ 97.266450] 1 lock held by udevd/198: >>> [ 97.266924] #0: (ptrval) (&mm->mmap_sem){....}, at: __do_munmap+0x531/0x730 >> I have not figured out what this is caused by. But, the below warning looks >> more confusing. This might be caused by the below one. > I *think* we need to understand more about what detached VMAs mean for > rmap. The anon_vma for these VMAs still reachable for the rmap and > therefore VMA too. I don't quite grasp what is implications of this, but > it doesn't look good. I'm supposed before accessing anon_vma, VMA need to be found by find_vma() first, right? But, finding VMA need hold mmap_sem, once detach VMAs is called, others should not be able to find the VMAs anymore. So, the anon_vma should not be reachable except the munmap caller. > > I'll look into this more when I get some free cycles. I'm still traveling, will definitely look into it further once I'm back. Thanks, Yang > > It's better to disable the optimization for now (by ignoring 'downgrade' > in __do_munmap()). Before it hits release. >