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=-2.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 177BDC0650E for ; Wed, 3 Jul 2019 13:54:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D0DC5218A3 for ; Wed, 3 Jul 2019 13:54:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=toxicpanda-com.20150623.gappssmtp.com header.i=@toxicpanda-com.20150623.gappssmtp.com header.b="obWoRzRo" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726743AbfGCNyL (ORCPT ); Wed, 3 Jul 2019 09:54:11 -0400 Received: from mail-qk1-f174.google.com ([209.85.222.174]:35144 "EHLO mail-qk1-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726255AbfGCNyK (ORCPT ); Wed, 3 Jul 2019 09:54:10 -0400 Received: by mail-qk1-f174.google.com with SMTP id r21so2475602qke.2 for ; Wed, 03 Jul 2019 06:54:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=toxicpanda-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:subject:message-id:mime-version:content-disposition :user-agent; bh=gIEYRzqlwIwc7hUk2f2qx/ZlMqS8yR7su+z1FiOxXY0=; b=obWoRzRouPlnuk1N2QYS+tCj2fBQXzy5dv+imJRyhNLg7/9oiM3CeLHzVBTRCyCUfd SpfJTICJL18qhIoZtKN+h5BY6Xc6azcuc7YQzTbeXGUHrHjoJ2SoMCeZVEB6ZkT3t1QF o3YYyt3iGEeaGBdWZ7zx14aOMqDlnih/qXD9VYtO6ybP+xP3YN2ccjO54PoQ+SrcppSB uDY4tcXREew+UdE2tYNo64QheR0VElR6rWFqtf+iyszd209ymScZBseQ7vMQnQFBGwg6 c4i/K9upbI2eMSwe0F3F7FZFLQFAlQnBAQCqP0McZxIAXYtuTiyPdxYBLw90KUXmYuIL wYdw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:subject:message-id:mime-version :content-disposition:user-agent; bh=gIEYRzqlwIwc7hUk2f2qx/ZlMqS8yR7su+z1FiOxXY0=; b=tlbBBRd7F3iHGGIUPolg3eF4ZEYUpT+JOZyx45qV26ROwgfVS7+OOZagxBEu8A1oqB ov1U5wjpTvhNnDIgoM9FYFhIL1Qyz9qVLvpP/Ijp4botcRDIG/2pGVnefUSM0QJPxxM2 CpA64ruvqqdQV94vAiXwJEcSRLHSgDLXg+P5zzTianZ45DFZKLFMskMkdIC8GYuI/O/p TRkn9VWy212QY58U3sReOawgaj2GzcUFbKZonrtgpd3Rdl9zNJVzO87Ew5B1smPTGvFa CLd1AGd9b3OjaI3Fw2mTw88E01iQZiaXwlA8y3xTCDpBieclL/cqXBm6A9jnWJHvFq/s 3KlA== X-Gm-Message-State: APjAAAX/B+zBrUMARwvaj+0+upbSGrX/StjyzfCeaf/hKuia8EFy4zNv EZfDRlbKTtZHaVLw4jECi1/raA== X-Google-Smtp-Source: APXvYqzM5pzh3+qWa0g9z5tHVE/8f0W5Z8VZPA2Awim5MX2pD/agUO8GT8O16VR3K5LLf+cFv+OmEA== X-Received: by 2002:a37:a6c9:: with SMTP id p192mr32234615qke.184.1562162048970; Wed, 03 Jul 2019 06:54:08 -0700 (PDT) Received: from localhost ([2620:10d:c091:480::c14f]) by smtp.gmail.com with ESMTPSA id s134sm873214qke.51.2019.07.03.06.54.07 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 03 Jul 2019 06:54:08 -0700 (PDT) Date: Wed, 3 Jul 2019 09:54:06 -0400 From: Josef Bacik To: peterz@infradead.org, mingo@kernel.org, linux-btrfs@vger.kernel.org Subject: Need help with a lockdep splat, possibly perf related? Message-ID: <20190703135405.kwzg2am7voldx7ac@macbook-pro-91.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: NeoMutt/20180716 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Hello, I've been seeing a variation of the following splat recently and I have no earthly idea what it's trying to tell me. I either get this one, or I get one that tells me the same thing except it's complaining about &cpuctx_mutex instead of sb_pagefaults. There is no place we take the reloc_mutex and then do the pagefaults stuff, so I don't know where it's getting these dependencies from. The stacktraces make no sense because there's perf stuff in here, but it doesn't show me a path where we would be holding _any_ btrfs locks, so I'm not sure how we gain those dependencies. Can you tell me where I'm being stupid? Thanks, ====================================================== WARNING: possible circular locking dependency detected 5.2.0-rc7-00100-ga4067edd7814 #671 Not tainted ------------------------------------------------------ python3.6/44461 is trying to acquire lock: 00000000674af011 (&fs_info->reloc_mutex){+.+.}, at: btrfs_record_root_in_trans+0x3c/0x70 but task is already holding lock: 0000000091a6f027 (sb_pagefaults){.+.+}, at: btrfs_page_mkwrite+0x6a/0x4f0 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #10 (sb_pagefaults){.+.+}: __sb_start_write+0x12f/0x1d0 btrfs_page_mkwrite+0x6a/0x4f0 do_page_mkwrite+0x2b/0x70 __handle_mm_fault+0x6f2/0x10e0 handle_mm_fault+0x179/0x360 __do_page_fault+0x24d/0x4d0 page_fault+0x1e/0x30 -> #9 (&mm->mmap_sem#2){++++}: __might_fault+0x6b/0x90 _copy_to_user+0x1e/0x70 perf_read+0x1a9/0x2c0 vfs_read+0x9b/0x150 ksys_read+0x5c/0xd0 do_syscall_64+0x4a/0x1b0 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #8 (&cpuctx_mutex){+.+.}: __mutex_lock+0x81/0x8f0 perf_event_init_cpu+0x9c/0x150 perf_event_init+0x1d0/0x1fe start_kernel+0x365/0x513 secondary_startup_64+0xa4/0xb0 -> #7 (pmus_lock){+.+.}: __mutex_lock+0x81/0x8f0 perf_event_init_cpu+0x69/0x150 cpuhp_invoke_callback+0xb8/0x950 _cpu_up.constprop.29+0xad/0x140 do_cpu_up+0x92/0xe0 smp_init+0xcf/0xd4 kernel_init_freeable+0x13a/0x290 kernel_init+0xa/0x110 ret_from_fork+0x24/0x30 -> #6 (cpu_hotplug_lock.rw_sem){++++}: cpus_read_lock+0x43/0x90 kmem_cache_create_usercopy+0x28/0x250 kmem_cache_create+0x18/0x20 bioset_init+0x157/0x2a0 init_bio+0xa1/0xa7 do_one_initcall+0x67/0x2f4 kernel_init_freeable+0x1ec/0x290 kernel_init+0xa/0x110 ret_from_fork+0x24/0x30 -> #5 (bio_slab_lock){+.+.}: __mutex_lock+0x81/0x8f0 bioset_init+0xb0/0x2a0 blk_alloc_queue_node+0x80/0x2d0 blk_mq_init_queue+0x1b/0x60 0xffffffffa0022131 do_one_initcall+0x67/0x2f4 do_init_module+0x5a/0x22e load_module+0x1ebc/0x2570 __do_sys_finit_module+0xb2/0xc0 do_syscall_64+0x4a/0x1b0 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #4 (loop_ctl_mutex){+.+.}: __mutex_lock+0x81/0x8f0 __blkdev_get+0xba/0x530 blkdev_get+0x1bd/0x340 do_dentry_open+0x1fb/0x390 path_openat+0x4f7/0xd30 do_filp_open+0x91/0x100 do_sys_open+0x127/0x220 do_syscall_64+0x4a/0x1b0 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #3 (&bdev->bd_mutex){+.+.}: __mutex_lock+0x81/0x8f0 __blkdev_get+0x158/0x530 blkdev_get+0x21f/0x340 blkdev_get_by_path+0x4a/0x80 btrfs_get_bdev_and_sb+0x1b/0xb0 open_fs_devices+0x15d/0x290 btrfs_open_devices+0x75/0xa0 btrfs_mount_root+0x237/0x680 legacy_get_tree+0x2d/0x50 vfs_get_tree+0x1e/0x100 fc_mount+0xe/0x40 vfs_kern_mount+0x7c/0x90 btrfs_mount+0x15b/0x82d legacy_get_tree+0x2d/0x50 vfs_get_tree+0x1e/0x100 do_mount+0x6ee/0xab0 ksys_mount+0x7e/0xd0 __x64_sys_mount+0x21/0x30 do_syscall_64+0x4a/0x1b0 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #2 (&fs_devs->device_list_mutex){+.+.}: __mutex_lock+0x81/0x8f0 btrfs_run_dev_stats+0x4d/0x3c0 commit_cowonly_roots+0xb2/0x2a0 btrfs_commit_transaction+0x524/0xa80 btrfs_recover_log_trees+0x366/0x470 open_ctree+0x20a1/0x22dd btrfs_mount_root+0x51e/0x680 legacy_get_tree+0x2d/0x50 vfs_get_tree+0x1e/0x100 fc_mount+0xe/0x40 vfs_kern_mount+0x7c/0x90 btrfs_mount+0x15b/0x82d legacy_get_tree+0x2d/0x50 vfs_get_tree+0x1e/0x100 do_mount+0x6ee/0xab0 ksys_mount+0x7e/0xd0 __x64_sys_mount+0x21/0x30 do_syscall_64+0x4a/0x1b0 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&fs_info->tree_log_mutex){+.+.}: __mutex_lock+0x81/0x8f0 btrfs_commit_transaction+0x4c9/0xa80 btrfs_recover_log_trees+0x366/0x470 open_ctree+0x20a1/0x22dd btrfs_mount_root+0x51e/0x680 legacy_get_tree+0x2d/0x50 vfs_get_tree+0x1e/0x100 fc_mount+0xe/0x40 vfs_kern_mount+0x7c/0x90 btrfs_mount+0x15b/0x82d legacy_get_tree+0x2d/0x50 vfs_get_tree+0x1e/0x100 do_mount+0x6ee/0xab0 ksys_mount+0x7e/0xd0 __x64_sys_mount+0x21/0x30 do_syscall_64+0x4a/0x1b0 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&fs_info->reloc_mutex){+.+.}: lock_acquire+0xb0/0x1a0 __mutex_lock+0x81/0x8f0 btrfs_record_root_in_trans+0x3c/0x70 start_transaction+0xaa/0x510 btrfs_dirty_inode+0x49/0xe0 file_update_time+0xc7/0x110 btrfs_page_mkwrite+0x152/0x4f0 do_page_mkwrite+0x2b/0x70 do_wp_page+0x4b1/0x5e0 __handle_mm_fault+0x6b8/0x10e0 handle_mm_fault+0x179/0x360 __do_page_fault+0x24d/0x4d0 page_fault+0x1e/0x30 other info that might help us debug this: Chain exists of: &fs_info->reloc_mutex --> &mm->mmap_sem#2 --> sb_pagefaults Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sb_pagefaults); lock(&mm->mmap_sem#2); lock(sb_pagefaults); lock(&fs_info->reloc_mutex); *** DEADLOCK *** 3 locks held by python3.6/44461: #0: 000000005a6ec7ac (&mm->mmap_sem#2){++++}, at: __do_page_fault+0x13d/0x4d0 #1: 0000000091a6f027 (sb_pagefaults){.+.+}, at: btrfs_page_mkwrite+0x6a/0x4f0 #2: 00000000a7f74f74 (sb_internal){.+.+}, at: start_transaction+0x36b/0x510 stack backtrace: CPU: 10 PID: 44461 Comm: python3.6 Kdump: loaded Not tainted 5.2.0-rc7-00100-ga4067edd7814 #671 Hardware name: Quanta Leopard ORv2-DDR4/Leopard ORv2-DDR4, BIOS F06_3B17 03/16/2018 Call Trace: dump_stack+0x5e/0x8b print_circular_bug+0x1f1/0x1fe __lock_acquire+0x1724/0x1970 ? find_held_lock+0x31/0xa0 lock_acquire+0xb0/0x1a0 ? btrfs_record_root_in_trans+0x3c/0x70 ? btrfs_record_root_in_trans+0x3c/0x70 __mutex_lock+0x81/0x8f0 ? btrfs_record_root_in_trans+0x3c/0x70 ? find_held_lock+0x31/0xa0 ? btrfs_record_root_in_trans+0x3c/0x70 ? join_transaction+0x39f/0x3f0 btrfs_record_root_in_trans+0x3c/0x70 start_transaction+0xaa/0x510 btrfs_dirty_inode+0x49/0xe0 ? current_time+0x46/0x80 file_update_time+0xc7/0x110 btrfs_page_mkwrite+0x152/0x4f0 ? find_held_lock+0x31/0xa0 ? do_wp_page+0x4a9/0x5e0 do_page_mkwrite+0x2b/0x70 do_wp_page+0x4b1/0x5e0 __handle_mm_fault+0x6b8/0x10e0 handle_mm_fault+0x179/0x360 ? handle_mm_fault+0x46/0x360 __do_page_fault+0x24d/0x4d0 ? page_fault+0x8/0x30 page_fault+0x1e/0x30 RIP: 0033:0x7fe888361860 Code: 00 48 89 df e8 e1 2b ff ff 48 89 c3 48 83 f8 ff 74 2b 4c 89 e1 45 0f b7 45 00 0f b7 c0 48 c1 f9 10 75 4b 48 8b 05 18 d7 20 00 <66> 41 89 5d 00 48 ff 00 48 83 c4 08 5b 41 5c 41 5d 5d c3 e8 a8 2c RSP: 002b:00007fff4ab2ea70 EFLAGS: 00010246 RAX: 00007fe8b101c110 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 00007fe8b1538708 RSI: 00007fe8b1014040 RDI: 00007fe8b1066d00 RBP: 00007fff4ab2ea90 R08: 0000000000000000 R09: 0000000000000000 R10: 00007fe8885843e0 R11: 00007fe8b1026540 R12: 0000000000000002 R13: 00007fe8b138e000 R14: 00007fe886ace730 R15: 00007fe8b1066d00