Re: [syzbot] INFO: task hung in nfc_rfkill_set_block

Hi,

This looks like the device_lock vs rfkill_global_mutex inversion
fixed by 1ab526d97a57 ("net: nfc: fix deadlock between
nfc_unregister_device and rfkill_fop_write"). That fix credited a
different syzbot report, so this one was never linked to it.

I ran the C reproducer for 600 s per kernel, x86_64 under QEMU/KVM:

  1ab526d97a57^  hung task report at 91 s (rfkill_sync_work in
                 nfc_dev_down, nfc_unregister_device in
                 rfkill_unregister)
  1ab526d97a57   no hang
  9d66f26fefac   no hang (mainline)

#syz fix: net: nfc: fix deadlock between nfc_unregister_device and rfkill_fop_write

Thanks,
Magnus