Hello,
I'm looking at a report from the fleet (don't have a reproducer)
and wondering what you and block folks might think / suggest.
The problem is basically as follows
CPU0
do_syscall
sys_close
__fput
blkdev_release
blkdev_put grabs ->open_mutex
sr_block_release
scsi_set_medium_removal
ioctl_internal_command
scsi_execute_cmd
scsi_alloc_request
blk_mq_alloc_request
blk_queue_enter
schedule
at the same time:
CPU1
usb_disconnect
usb_disable_device
device_del
usb_unbind_interface
usb_stor_disconnect
scsi_remove_host
scsi_forget_host
__scsi_remove_device
device_del
bus_remove_device
device_release_driver_internal
sr_remove
del_gendisk
mutex_lock attempts to grab ->open_mutex
schedule
blk_queue_enter() sleeps forever, under ->open_mutex, there is no
way for it to be woken up and to detect blk_queue_dying(). del_gendisk()
sleeps forever because it attempts to grab ->open_mutex before it calls
__blk_mark_disk_dead(), which would mark the queue QUEUE_FLAG_DYING and
wake up ->mq_freeze_wq (which is blk_queue_enter() in this case).
I wonder how to fix it. My current "patch" is to set QUEUE_FLAG_DYING
and "kick" ->mq_freeze_wq early on in del_gendisk(), before it attempts
to grab ->open_mutex for the first time.
Any suggestions?
