Debian GNU/Linux 7 syzkaller ttyS0 net.ipv6.conf.syz0.accept_dad = 0 net.ipv6.conf.syz0.router_solicitations = 0 executing program executing program executing program syzkaller login: [ 29.750798] [ 29.750977] ====================================================== [ 29.751505] WARNING: possible circular locking dependency detected [ 29.752087] 4.13.0-rc6-next-20170825+ #9 Not tainted [ 29.752557] ------------------------------------------------------ [ 29.753152] kworker/0:1/37 is trying to acquire lock: [ 29.753517] ((shepherd).work){+.+.}, at: [] process_one_work+0xb2c/0x1be0 [ 29.754116] [ 29.754116] but now in release context of a crosslock acquired at the following: [ 29.754810] ((complete)&rcu.completion){+.+.}, at: [] __synchronize_srcu+0x1b5/0x250 [ 29.755520] [ 29.755520] which lock already depends on the new lock. [ 29.755520] [ 29.756168] [ 29.756168] the existing dependency chain (in reverse order) is: [ 29.756760] [ 29.756760] -> #2 ((complete)&rcu.completion){+.+.}: [ 29.757270] __lock_acquire+0x3286/0x4620 [ 29.757633] lock_acquire+0x1d5/0x580 [ 29.757945] wait_for_completion+0xc8/0x770 [ 29.758305] __synchronize_srcu+0x1b5/0x250 [ 29.758705] synchronize_srcu+0x1a3/0x560 [ 29.759130] quarantine_remove_cache+0xd7/0xf0 [ 29.759494] kasan_cache_shrink+0x9/0x10 [ 29.759823] kmem_cache_shrink+0x15/0x30 [ 29.760125] acpi_os_purge_cache+0x15/0x20 [ 29.760494] acpi_purge_cached_objects+0x38/0xc9 [ 29.760921] acpi_initialize_objects+0xc5/0x112 [ 29.761288] acpi_init+0x23c/0x8e6 [ 29.761626] do_one_initcall+0x9e/0x330 [ 29.762019] kernel_init_freeable+0x469/0x521 [ 29.762347] kernel_init+0x13/0x172 [ 29.763207] ret_from_fork+0x2a/0x40 [ 29.763501] [ 29.763501] -> #1 (cpu_hotplug_lock.rw_sem){++++}: [ 29.763930] __lock_acquire+0x3286/0x4620 [ 29.764292] lock_acquire+0x1d5/0x580 [ 29.764577] cpus_read_lock+0x42/0x90 [ 29.764889] vmstat_shepherd+0x3d/0x1b0 [ 29.765212] process_one_work+0xbfd/0x1be0 [ 29.765524] worker_thread+0x223/0x1860 [ 29.765833] kthread+0x39c/0x470 [ 29.766130] ret_from_fork+0x2a/0x40 [ 29.766433] [ 29.766433] -> #0 ((shepherd).work){+.+.}: [ 29.766835] process_one_work+0xba5/0x1be0 [ 29.767147] worker_thread+0x223/0x1860 [ 29.767442] kthread+0x39c/0x470 [ 29.767696] ret_from_fork+0x2a/0x40 [ 29.767973] 0xffffffffffffffff [ 29.768261] [ 29.768261] other info that might help us debug this: [ 29.768261] [ 29.768795] Chain exists of: [ 29.768795] (shepherd).work --> cpu_hotplug_lock.rw_sem --> (complete)&rcu.completion [ 29.768795] [ 29.769656] Possible unsafe locking scenario by crosslock: [ 29.769656] [ 29.770207] CPU0 CPU1 [ 29.770523] ---- ---- [ 29.770827] lock(cpu_hotplug_lock.rw_sem); [ 29.771118] lock((complete)&rcu.completion); [ 29.771472] lock((shepherd).work); [ 29.771880] unlock((complete)&rcu.completion); [ 29.772407] [ 29.772407] *** DEADLOCK *** [ 29.772407] [ 29.772811] 3 locks held by kworker/0:1/37: [ 29.773092] #0: ("events_power_efficient"){.+.+}, at: [] process_one_work+0xad4/0x1be0 [ 29.773733] #1: ((&(&sdp->work)->work)){+.+.}, at: [] process_one_work+0xb2c/0x1be0 [ 29.774371] #2: (&x->wait#5){....}, at: [] complete+0x18/0x80 [ 29.774887] [ 29.774887] stack backtrace: [ 29.775228] CPU: 0 PID: 37 Comm: kworker/0:1 Not tainted 4.13.0-rc6-next-20170825+ #9 [ 29.775815] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 [ 29.776355] Workqueue: events_power_efficient srcu_invoke_callbacks [ 29.776841] Call Trace: [ 29.777056] dump_stack+0x194/0x257 [ 29.777325] ? arch_local_irq_restore+0x53/0x53 [ 29.777649] print_circular_bug+0x503/0x710 [ 29.777951] ? print_circular_bug_entry+0xb0/0xb0 [ 29.778306] check_prev_add+0x865/0x1520 [ 29.778619] ? trace_hardirqs_on+0xd/0x10 [ 29.778951] ? _raw_spin_unlock_irq+0x27/0x70 [ 29.779315] ? graph_lock+0x170/0x170 [ 29.779595] ? check_usage+0xb70/0xb70 [ 29.779880] ? find_held_lock+0x39/0x1d0 [ 29.780176] ? hlock_class+0x140/0x140 [ 29.780448] ? srcu_reschedule+0x130/0x130 [ 29.780769] ? find_next_bit+0x27/0x30 [ 29.781068] lock_commit_crosslock+0xe73/0x1d10 [ 29.781377] ? lock_commit_crosslock+0xe73/0x1d10 [ 29.781769] ? check_prev_add+0x1520/0x1520 [ 29.782125] ? lock_acquire+0x1d5/0x580 [ 29.782416] ? complete+0x18/0x80 [ 29.782663] ? lock_release+0xd70/0xd70 [ 29.782953] ? check_noncircular+0x20/0x20 [ 29.783235] ? do_raw_spin_trylock+0x190/0x190 [ 29.783611] complete+0x24/0x80 [ 29.783830] wakeme_after_rcu+0xd/0x10 [ 29.784347] srcu_invoke_callbacks+0x280/0x4d0 [ 29.784651] ? srcu_queue_delayed_work_on+0x240/0x240 [ 29.784991] ? __lock_is_held+0xbc/0x140 [ 29.785263] process_one_work+0xbfd/0x1be0 [ 29.785543] ? check_noncircular+0x20/0x20 [ 29.785826] ? pwq_dec_nr_in_flight+0x450/0x450 [ 29.786135] ? finish_task_switch+0x1d3/0x740 [ 29.786532] ? __sched_text_start+0x8/0x8 [ 29.786858] ? check_noncircular+0x20/0x20 [ 29.787196] ? unwind_next_frame+0x3e/0x50 [ 29.787536] ? find_held_lock+0x39/0x1d0 [ 29.787860] ? lock_acquire+0x1d5/0x580 [ 29.788193] ? worker_thread+0x4a3/0x1860 [ 29.788524] ? lock_downgrade+0x990/0x990 [ 29.788853] ? lock_release+0xd70/0xd70 [ 29.789152] ? do_raw_spin_trylock+0x190/0x190 [ 29.789526] ? find_held_lock+0x39/0x1d0 [ 29.789874] worker_thread+0x223/0x1860 [ 29.790231] ? process_one_work+0x1be0/0x1be0 [ 29.790554] ? check_noncircular+0x20/0x20 [ 29.790865] ? _raw_spin_unlock_irq+0x27/0x70 [ 29.791186] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 29.791654] ? trace_hardirqs_on+0xd/0x10 [ 29.791952] ? _raw_spin_unlock_irq+0x27/0x70 [ 29.792271] ? finish_task_switch+0x1d3/0x740 [ 29.792603] ? finish_task_switch+0x1aa/0x740 [ 29.792934] ? preempt_notifier_dec+0x20/0x20 [ 29.793260] ? __schedule+0x8f0/0x2070 [ 29.793540] ? __x2apic_send_IPI_dest.constprop.7+0x5b/0x80 [ 29.793954] ? try_to_wake_up+0xf9/0x1600 [ 29.794252] ? lock_commit_crosslock+0xe73/0x1d10 [ 29.794608] ? find_held_lock+0x39/0x1d0 [ 29.794898] ? lock_downgrade+0x990/0x990 [ 29.795174] ? complete+0x18/0x80 [ 29.795404] ? __schedule+0x2070/0x2070 [ 29.795670] ? _raw_spin_unlock_irqrestore+0x31/0xba [ 29.796008] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 29.796341] ? trace_hardirqs_on+0xd/0x10 [ 29.796631] ? __kthread_parkme+0x173/0x240 [ 29.796991] kthread+0x39c/0x470 [ 29.797271] ? process_one_work+0x1be0/0x1be0 [ 29.797658] ? kthread_create_on_node+0x100/0x100 [ 29.798058] ret_from_fork+0x2a/0x40 executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program