On Tue, Aug 20, 2019 at 02:07:43PM -0700, Bart Van Assche wrote: > On 8/19/19 1:15 AM, Ming Lei wrote: > > hctx->tags is tagset wide or host-wide, which is protected by set->tag_list_lock. > > Isn't the purpose of set->tag_list_lock to protect set->tag_list? In theory, .tags is shared among all queues in tagset, so it should be protected by tagset wide lock, what is why set->tag_list_lock is held in blk_mq_update_nr_hw_queues(). However, both sysfs and debugfs read/write doesn't hold this lock because the .tags won't be shrunk in blk_mq_update_nr_requests(), and blk_mq_update_nr_hw_queues un-registers debugfs/sysfs before changing .tags. thanks, Ming
