====================================================== WARNING: possible circular locking dependency detected 4.13.0-rc6-next-20170825+ #9 Not tainted ------------------------------------------------------ kworker/1:2/1314 is trying to acquire lock: ((delayed_fput_work).work){+.+.}, at: [] process_one_work+0xb2c/0x1be0 kernel/workqueue.c:2094 but now in release context of a crosslock acquired at the following: ((complete)wq_barr::done/1){+.+.}, at: [] flush_work+0x621/0x930 kernel/workqueue.c:2868 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #6 ((complete)wq_barr::done/1){+.+.}: check_prevs_add kernel/locking/lockdep.c:2020 [inline] validate_chain kernel/locking/lockdep.c:2469 [inline] __lock_acquire+0x3286/0x4620 kernel/locking/lockdep.c:3498 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002 complete_acquire include/linux/completion.h:39 [inline] __wait_for_common kernel/sched/completion.c:108 [inline] wait_for_common kernel/sched/completion.c:122 [inline] wait_for_completion+0xc8/0x770 kernel/sched/completion.c:143 flush_work+0x621/0x930 kernel/workqueue.c:2868 lru_add_drain_all_cpuslocked+0x331/0x520 mm/swap.c:722 lru_add_drain_all+0x13/0x20 mm/swap.c:730 SYSC_mlockall mm/mlock.c:803 [inline] SyS_mlockall+0x2fb/0x670 mm/mlock.c:791 entry_SYSCALL_64_fastpath+0x1f/0xbe -> #5 (lock#5){+.+.}: check_prevs_add kernel/locking/lockdep.c:2020 [inline] validate_chain kernel/locking/lockdep.c:2469 [inline] __lock_acquire+0x3286/0x4620 kernel/locking/lockdep.c:3498 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0x16f/0x1870 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 lru_add_drain_all_cpuslocked+0xb3/0x520 mm/swap.c:704 lru_add_drain_all+0x13/0x20 mm/swap.c:730 SYSC_mlockall mm/mlock.c:803 [inline] SyS_mlockall+0x2fb/0x670 mm/mlock.c:791 entry_SYSCALL_64_fastpath+0x1f/0xbe -> #4 (cpu_hotplug_lock.rw_sem){++++}: check_prevs_add kernel/locking/lockdep.c:2020 [inline] validate_chain kernel/locking/lockdep.c:2469 [inline] __lock_acquire+0x3286/0x4620 kernel/locking/lockdep.c:3498 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002 percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:35 [inline] percpu_down_read include/linux/percpu-rwsem.h:58 [inline] cpus_read_lock+0x42/0x90 kernel/cpu.c:218 get_online_cpus include/linux/cpu.h:126 [inline] kmem_cache_create+0x26/0x2a0 mm/slab_common.c:431 bio_find_or_create_slab block/bio.c:115 [inline] bioset_create+0x42c/0x850 block/bio.c:1981 init_bio+0x193/0x1b6 block/bio.c:2125 do_one_initcall+0x9e/0x330 init/main.c:826 do_initcall_level init/main.c:892 [inline] do_initcalls init/main.c:900 [inline] do_basic_setup init/main.c:918 [inline] kernel_init_freeable+0x469/0x521 init/main.c:1066 kernel_init+0x13/0x172 init/main.c:993 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431 -> #3 (bio_slab_lock){+.+.}: check_prevs_add kernel/locking/lockdep.c:2020 [inline] validate_chain kernel/locking/lockdep.c:2469 [inline] __lock_acquire+0x3286/0x4620 kernel/locking/lockdep.c:3498 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0x16f/0x1870 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 bio_find_or_create_slab block/bio.c:80 [inline] bioset_create+0x261/0x850 block/bio.c:1981 blk_alloc_queue_node+0x139/0xba0 block/blk-core.c:826 blk_mq_init_queue+0x46/0x90 block/blk-mq.c:2264 loop_add+0x2f0/0x990 drivers/block/loop.c:1796 loop_init+0x1ae/0x20a drivers/block/loop.c:2056 do_one_initcall+0x9e/0x330 init/main.c:826 do_initcall_level init/main.c:892 [inline] do_initcalls init/main.c:900 [inline] do_basic_setup init/main.c:918 [inline] kernel_init_freeable+0x469/0x521 init/main.c:1066 kernel_init+0x13/0x172 init/main.c:993 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431 -> #2 (loop_index_mutex){+.+.}: check_prevs_add kernel/locking/lockdep.c:2020 [inline] validate_chain kernel/locking/lockdep.c:2469 [inline] __lock_acquire+0x3286/0x4620 kernel/locking/lockdep.c:3498 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0x16f/0x1870 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 lo_open+0x1b/0xa0 drivers/block/loop.c:1586 __blkdev_get+0x2f9/0xf90 fs/block_dev.c:1464 blkdev_get+0x3a1/0xad0 fs/block_dev.c:1601 blkdev_open+0x1ff/0x2c0 fs/block_dev.c:1757 do_dentry_open+0x67f/0xd70 fs/open.c:752 vfs_open+0x107/0x220 fs/open.c:866 do_last fs/namei.c:3388 [inline] path_openat+0x1157/0x3520 fs/namei.c:3528 do_filp_open+0x25b/0x3b0 fs/namei.c:3563 do_sys_open+0x502/0x6d0 fs/open.c:1059 SYSC_open fs/open.c:1077 [inline] SyS_open+0x2d/0x40 fs/open.c:1072 entry_SYSCALL_64_fastpath+0x1f/0xbe -> #1 (&bdev->bd_mutex){+.+.}: check_prevs_add kernel/locking/lockdep.c:2020 [inline] validate_chain kernel/locking/lockdep.c:2469 [inline] __lock_acquire+0x3286/0x4620 kernel/locking/lockdep.c:3498 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0x16f/0x1870 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 blkdev_put+0x2a/0x4f0 fs/block_dev.c:1801 blkdev_close+0x91/0xc0 fs/block_dev.c:1850 __fput+0x333/0x7f0 fs/file_table.c:210 delayed_fput+0x44/0x70 fs/file_table.c:240 process_one_work+0xbfd/0x1be0 kernel/workqueue.c:2098 worker_thread+0x223/0x1860 kernel/workqueue.c:2233 kthread+0x39c/0x470 kernel/kthread.c:231 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431 -> #0 ((delayed_fput_work).work){+.+.}: process_one_work+0xba5/0x1be0 kernel/workqueue.c:2095 worker_thread+0x223/0x1860 kernel/workqueue.c:2233 kthread+0x39c/0x470 kernel/kthread.c:231 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431 0xffffffffffffffff other info that might help us debug this: Chain exists of: (delayed_fput_work).work --> lock#5 --> (complete)wq_barr::done/1 Possible unsafe locking scenario by crosslock: CPU0 CPU1 ---- ---- lock(lock#5); lock((complete)wq_barr::done/1); lock((delayed_fput_work).work); unlock((complete)wq_barr::done/1); *** DEADLOCK *** 3 locks held by kworker/1:2/1314: #0: ("mm_percpu_wq"){++++}, at: [] __write_once_size include/linux/compiler.h:305 [inline] #0: ("mm_percpu_wq"){++++}, at: [] atomic64_set arch/x86/include/asm/atomic64_64.h:33 [inline] #0: ("mm_percpu_wq"){++++}, at: [] atomic_long_set include/asm-generic/atomic-long.h:56 [inline] #0: ("mm_percpu_wq"){++++}, at: [] set_work_data kernel/workqueue.c:617 [inline] #0: ("mm_percpu_wq"){++++}, at: [] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: ("mm_percpu_wq"){++++}, at: [] process_one_work+0xad4/0x1be0 kernel/workqueue.c:2090 #1: ((&barr->work)){+.+.}, at: [] process_one_work+0xb2c/0x1be0 kernel/workqueue.c:2094 #2: (&x->wait#14){....}, at: [] complete+0x18/0x80 kernel/sched/completion.c:34 stack backtrace: CPU: 1 PID: 1314 Comm: kworker/1:2 Not tainted 4.13.0-rc6-next-20170825+ #9 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Workqueue: mm_percpu_wq wq_barrier_func Call Trace: __dump_stack lib/dump_stack.c:16 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:52 print_circular_bug+0x503/0x710 kernel/locking/lockdep.c:1259 check_prev_add+0x865/0x1520 kernel/locking/lockdep.c:1894 commit_xhlock kernel/locking/lockdep.c:5002 [inline] commit_xhlocks kernel/locking/lockdep.c:5046 [inline] lock_commit_crosslock+0xe73/0x1d10 kernel/locking/lockdep.c:5085 complete_release_commit include/linux/completion.h:49 [inline] complete+0x24/0x80 kernel/sched/completion.c:39 wq_barrier_func+0x16/0x20 kernel/workqueue.c:2437 process_one_work+0xbfd/0x1be0 kernel/workqueue.c:2098 process_scheduled_works kernel/workqueue.c:2159 [inline] worker_thread+0xa4b/0x1860 kernel/workqueue.c:2238 kthread+0x39c/0x470 kernel/kthread.c:231 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431