On Thu, Oct 03, 2024 at 05:56:10PM +0900, Sergey Senozhatsky wrote: > 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. We split blk_queue_enter further to distinguish between file system requests and passthrough ones. The file system request should be using bio_queue_enter, which only checks GD_DEAD, instead of QUEUE_FLAG_DYING. Passthrough requests like the cdrom door lock are using blk_queue_enter that checks QUEUE_FLAG_DYING which only gets set in blk_mq_destroy_queue. So AFAICS your trace should not happen with the current kernel, but probably could happen with older stable version unless I'm missing something. What kernel version did you see this on?
