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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id b20sm42520585qkb.17.2019.01.09.05.37.30 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 09 Jan 2019 05:37:31 -0800 (PST) Subject: Re: lockdep warning while reading sysfs To: Peter Zijlstra Cc: viro@zeniv.linux.org.uk, gregkh@linuxfoundation.org, tj@kernel.org, linux-kernel@vger.kernel.org, Linux-MM References: <2c9aaa31-d0b7-bc20-f109-751a2fccfb88@lca.pw> <20190109084441.GF1900@hirez.programming.kicks-ass.net> From: Qian Cai Message-ID: Date: Wed, 9 Jan 2019 08:37:30 -0500 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.3.3 MIME-Version: 1.0 In-Reply-To: <20190109084441.GF1900@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > You stripped out the stack trace at the bottom that shows the inversion > :/ > Sorry, I thought it is the same as in #0, but here it is the whole thing. WARNING: possible circular locking dependency detected 5.0.0-rc1+ #60 Not tainted ------------------------------------------------------ read_all/2954 is trying to acquire lock: 00000000c63ff499 (mem_hotplug_lock.rw_sem){++++}, at: show_slab_objects+0x16c/0x450 but task is already holding lock: 0000000047ae17d7 (kn->count#70){++++}, at: kernfs_seq_start+0x79/0x170 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (kn->count#70){++++}: __lock_acquire+0x728/0x1200 lock_acquire+0x269/0x5a0 __kernfs_remove+0x72f/0x9a0 kernfs_remove_by_name_ns+0x45/0x90 sysfs_remove_link+0x3c/0xa0 sysfs_slab_add+0x1bd/0x330 __kmem_cache_create+0x166/0x1c0 create_cache+0xcf/0x1f0 kmem_cache_create_usercopy+0x1aa/0x270 kmem_cache_create+0x16/0x20 mlx5_init_fs+0x195/0x1a10 [mlx5_core] mlx5_load_one+0x1106/0x1e90 [mlx5_core] init_one+0x864/0xd60 [mlx5_core] local_pci_probe+0xda/0x190 work_for_cpu_fn+0x56/0xa0 process_one_work+0xad7/0x1b80 worker_thread+0x8ff/0x1370 kthread+0x32c/0x3f0 ret_from_fork+0x27/0x50 -> #2 (slab_mutex){+.+.}: __lock_acquire+0x728/0x1200 lock_acquire+0x269/0x5a0 __mutex_lock+0x168/0x1730 mutex_lock_nested+0x1b/0x20 kmem_cache_create_usercopy+0x45/0x270 kmem_cache_create+0x16/0x20 ptlock_cache_init+0x24/0x2d start_kernel+0x40e/0x7e0 x86_64_start_reservations+0x24/0x26 x86_64_start_kernel+0xef/0xf6 secondary_startup_64+0xb6/0xc0 -> #1 (memcg_cache_ids_sem){++++}: __lock_acquire+0x728/0x1200 lock_acquire+0x269/0x5a0 down_read+0x92/0x130 memcg_get_cache_ids+0x15/0x20 kmem_cache_create_usercopy+0x37/0x270 kmem_cache_create+0x16/0x20 ptlock_cache_init+0x24/0x2d start_kernel+0x40e/0x7e0 x86_64_start_reservations+0x24/0x26 x86_64_start_kernel+0xef/0xf6 secondary_startup_64+0xb6/0xc0 -> #0 (mem_hotplug_lock.rw_sem){++++}: validate_chain.isra.14+0x11af/0x3b50 __lock_acquire+0x728/0x1200 lock_acquire+0x269/0x5a0 get_online_mems+0x3d/0x80 show_slab_objects+0x16c/0x450 total_objects_show+0x13/0x20 slab_attr_show+0x1e/0x30 sysfs_kf_seq_show+0x1d5/0x470 kernfs_seq_show+0x1fa/0x2c0 seq_read+0x3f7/0x1050 kernfs_fop_read+0x126/0x650 __vfs_read+0xeb/0xf20 vfs_read+0x103/0x290 ksys_read+0xfa/0x260 __x64_sys_read+0x73/0xb0 do_syscall_64+0x18f/0xd23 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: lock(kn->count#70); lock(slab_mutex); lock(kn->count#70); lock(mem_hotplug_lock.rw_sem); *** DEADLOCK *** 3 locks held by read_all/2954: #0: 00000000e8745902 (&p->lock){+.+.}, at: seq_read+0x6b/0x1050 #1: 00000000bb9fa87a (&of->mutex){+.+.}, at: kernfs_seq_start+0x4f/0x170 #2: 0000000047ae17d7 (kn->count#70){++++}, at: kernfs_seq_start+0x79/0x170 stack backtrace: CPU: 100 PID: 2954 Comm: read_all Kdump: loaded Not tainted 5.0.0-rc1+ #60 Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 09/07/2018 Call Trace: dump_stack+0xe0/0x19a print_circular_bug.isra.10.cold.34+0x2f4/0x435 check_prev_add.constprop.19+0xca1/0x15f0 validate_chain.isra.14+0x11af/0x3b50 __lock_acquire+0x728/0x1200 lock_acquire+0x269/0x5a0 get_online_mems+0x3d/0x80 show_slab_objects+0x16c/0x450 total_objects_show+0x13/0x20 slab_attr_show+0x1e/0x30 sysfs_kf_seq_show+0x1d5/0x470 kernfs_seq_show+0x1fa/0x2c0 seq_read+0x3f7/0x1050 kernfs_fop_read+0x126/0x650 __vfs_read+0xeb/0xf20 vfs_read+0x103/0x290 ksys_read+0xfa/0x260 __x64_sys_read+0x73/0xb0 do_syscall_64+0x18f/0xd23 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f01b0000b12 Code: 94 20 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b6 0f 1f 80 00 00 00 00 f3 0f 1e fa 8b 05 36 d9 20 00 85 c0 75 12 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 56 c3 0f 1f 44 00 00 41 54 49 89 d4 55 48 89 RSP: 002b:00007ffd480fc058 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 00007ffd480fc100 RCX: 00007f01b0000b12 RDX: 00000000000003ff RSI: 00007ffd480fc500 RDI: 0000000000000003 RBP: 00007f01b040f000 R08: 0000000000000020 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003 R13: 00007ffd480fc500 R14: 0000000000000028 R15: 0000000000000003