syzbot

======================================================
WARNING: possible circular locking dependency detected
4.13.0-rc6-next-20170825+ #9 Not tainted
------------------------------------------------------
kworker/0:2/1376 is trying to acquire lock:
 ((shepherd).work){+.+.}, at: [<ffffffff8146858c>] process_one_work+0xb2c/0x1be0 kernel/workqueue.c:2094

but now in release context of a crosslock acquired at the following:
 ((complete)&rcu.completion){+.+.}, at: [<ffffffff815b4075>] __synchronize_srcu+0x1b5/0x250 kernel/rcu/srcutree.c:898

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 ((complete)&rcu.completion){+.+.}:
       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
       __synchronize_srcu+0x1b5/0x250 kernel/rcu/srcutree.c:898
       synchronize_srcu_expedited kernel/rcu/srcutree.c:923 [inline]
       synchronize_srcu+0x1a3/0x560 kernel/rcu/srcutree.c:974
       quarantine_remove_cache+0xd7/0xf0 mm/kasan/quarantine.c:327
       kasan_cache_shrink+0x9/0x10 mm/kasan/kasan.c:380
       kmem_cache_shrink+0x15/0x30 mm/slab_common.c:857
       acpi_os_purge_cache+0x15/0x20 drivers/acpi/osl.c:1560
       acpi_purge_cached_objects+0x38/0xc9 drivers/acpi/acpica/utxface.c:271
       acpi_initialize_objects+0xc5/0x112 drivers/acpi/acpica/utxfinit.c:302
       acpi_bus_init drivers/acpi/bus.c:1131 [inline]
       acpi_init+0x23c/0x8e6 drivers/acpi/bus.c:1220
       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

-> #1 (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]
       vmstat_shepherd+0x3d/0x1b0 mm/vmstat.c:1707
       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 ((shepherd).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:
  (shepherd).work --> cpu_hotplug_lock.rw_sem --> (complete)&rcu.completion

 Possible unsafe locking scenario by crosslock:

       CPU0                    CPU1
       ----                    ----
  lock(cpu_hotplug_lock.rw_sem);
  lock((complete)&rcu.completion);
                               lock((shepherd).work);
                               unlock((complete)&rcu.completion);

 *** DEADLOCK ***

3 locks held by kworker/0:2/1376:
 #0:  ("events_power_efficient"){.+.+}, at: [<ffffffff81468534>] __write_once_size include/linux/compiler.h:305 [inline]
 #0:  ("events_power_efficient"){.+.+}, at: [<ffffffff81468534>] atomic64_set arch/x86/include/asm/atomic64_64.h:33 [inline]
 #0:  ("events_power_efficient"){.+.+}, at: [<ffffffff81468534>] atomic_long_set include/asm-generic/atomic-long.h:56 [inline]
 #0:  ("events_power_efficient"){.+.+}, at: [<ffffffff81468534>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_power_efficient"){.+.+}, at: [<ffffffff81468534>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_power_efficient"){.+.+}, at: [<ffffffff81468534>] process_one_work+0xad4/0x1be0 kernel/workqueue.c:2090
 #1:  ((&(&sdp->work)->work)){+.+.}, at: [<ffffffff8146858c>] process_one_work+0xb2c/0x1be0 kernel/workqueue.c:2094
 #2:  (&x->wait#5){....}, at: [<ffffffff81528c68>] complete+0x18/0x80 kernel/sched/completion.c:34

stack backtrace:
CPU: 0 PID: 1376 Comm: kworker/0:2 Not tainted 4.13.0-rc6-next-20170825+ #9
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Workqueue: events_power_efficient srcu_invoke_callbacks
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
 wakeme_after_rcu+0xd/0x10 kernel/rcu/update.c:376
 srcu_invoke_callbacks+0x280/0x4d0 kernel/rcu/srcutree.c:1161
 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