Re: [PATCH] power: remove possible deadlock when unregistering power_supply

[Sebastian Reichel]

Hi,

On Mon, Jun 25, 2018 at 09:51:48AM +0200, Benjamin Tissoires wrote:
> If a device gets removed right after having registered a power_supply node,
> we might enter in a deadlock between the remove call (that has a lock on
> the parent device) and the deferred register work.
> 
> Allow the deferred register work to exit without taking the lock when
> we are in the remove state.
> 
> Stack trace on a Ubuntu 16.04:
> 
> [16072.109121] INFO: task kworker/u16:2:1180 blocked for more than 120 seconds.
> [16072.109127]       Not tainted 4.13.0-41-generic #46~16.04.1-Ubuntu
> [16072.109129] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [16072.109132] kworker/u16:2   D    0  1180      2 0x80000000
> [16072.109142] Workqueue: events_power_efficient power_supply_deferred_register_work
> [16072.109144] Call Trace:
> [16072.109152]  __schedule+0x3d6/0x8b0
> [16072.109155]  schedule+0x36/0x80
> [16072.109158]  schedule_preempt_disabled+0xe/0x10
> [16072.109161]  __mutex_lock.isra.2+0x2ab/0x4e0
> [16072.109166]  __mutex_lock_slowpath+0x13/0x20
> [16072.109168]  ? __mutex_lock_slowpath+0x13/0x20
> [16072.109171]  mutex_lock+0x2f/0x40
> [16072.109174]  power_supply_deferred_register_work+0x2b/0x50
> [16072.109179]  process_one_work+0x15b/0x410
> [16072.109182]  worker_thread+0x4b/0x460
> [16072.109186]  kthread+0x10c/0x140
> [16072.109189]  ? process_one_work+0x410/0x410
> [16072.109191]  ? kthread_create_on_node+0x70/0x70
> [16072.109194]  ret_from_fork+0x35/0x40
> [16072.109199] INFO: task test:2257 blocked for more than 120 seconds.
> [16072.109202]       Not tainted 4.13.0-41-generic #46~16.04.1-Ubuntu
> [16072.109204] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [16072.109206] test            D    0  2257   2256 0x00000004
> [16072.109208] Call Trace:
> [16072.109211]  __schedule+0x3d6/0x8b0
> [16072.109215]  schedule+0x36/0x80
> [16072.109218]  schedule_timeout+0x1f3/0x360
> [16072.109221]  ? check_preempt_curr+0x5a/0xa0
> [16072.109224]  ? ttwu_do_wakeup+0x1e/0x150
> [16072.109227]  wait_for_completion+0xb4/0x140
> [16072.109230]  ? wait_for_completion+0xb4/0x140
> [16072.109233]  ? wake_up_q+0x70/0x70
> [16072.109236]  flush_work+0x129/0x1e0
> [16072.109240]  ? worker_detach_from_pool+0xb0/0xb0
> [16072.109243]  __cancel_work_timer+0x10f/0x190
> [16072.109247]  ? device_del+0x264/0x310
> [16072.109250]  ? __wake_up+0x44/0x50
> [16072.109253]  cancel_delayed_work_sync+0x13/0x20
> [16072.109257]  power_supply_unregister+0x37/0xb0
> [16072.109260]  devm_power_supply_release+0x11/0x20
> [16072.109263]  release_nodes+0x110/0x200
> [16072.109266]  devres_release_group+0x7c/0xb0
> [16072.109274]  wacom_remove+0xc2/0x110 [wacom]
> [16072.109279]  hid_device_remove+0x6e/0xd0 [hid]
> [16072.109284]  device_release_driver_internal+0x158/0x210
> [16072.109288]  device_release_driver+0x12/0x20
> [16072.109291]  bus_remove_device+0xec/0x160
> [16072.109293]  device_del+0x1de/0x310
> [16072.109298]  hid_destroy_device+0x27/0x60 [hid]
> [16072.109303]  usbhid_disconnect+0x51/0x70 [usbhid]
> [16072.109308]  usb_unbind_interface+0x77/0x270
> [16072.109311]  device_release_driver_internal+0x158/0x210
> [16072.109315]  device_release_driver+0x12/0x20
> [16072.109318]  usb_driver_release_interface+0x77/0x80
> [16072.109321]  proc_ioctl+0x20f/0x250
> [16072.109325]  usbdev_do_ioctl+0x57f/0x1140
> [16072.109327]  ? __wake_up+0x44/0x50
> [16072.109331]  usbdev_ioctl+0xe/0x20
> [16072.109336]  do_vfs_ioctl+0xa4/0x600
> [16072.109339]  ? vfs_write+0x15a/0x1b0
> [16072.109343]  SyS_ioctl+0x79/0x90
> [16072.109347]  entry_SYSCALL_64_fastpath+0x24/0xab
> [16072.109349] RIP: 0033:0x7f20da807f47
> [16072.109351] RSP: 002b:00007ffc422ae398 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> [16072.109353] RAX: ffffffffffffffda RBX: 00000000010b8560 RCX: 00007f20da807f47
> [16072.109355] RDX: 00007ffc422ae3a0 RSI: 00000000c0105512 RDI: 0000000000000009
> [16072.109356] RBP: 0000000000000000 R08: 00007ffc422ae3e0 R09: 0000000000000010
> [16072.109357] R10: 00000000000000a6 R11: 0000000000000246 R12: 0000000000000000
> [16072.109359] R13: 00000000010b8560 R14: 00007ffc422ae2e0 R15: 0000000000000000
> 
> Reported-and-tested-by: Richard Hughes <rhughes@xxxxxxxxxx>
> Tested-by: Aaron Skomra <Aaron.Skomra@xxxxxxxxx>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
> ---

Thanks, added Fixes: tag and queued to power-supply-fixes.

-- Sebastian

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