On 3/19/18 12:46 PM, Bart Van Assche wrote: > scsi_device_quiesce() uses synchronize_rcu() to guarantee that the > effect of blk_set_preempt_only() will be visible for percpu_ref_tryget() > calls that occur after the queue unfreeze by using the approach > explained in https://lwn.net/Articles/573497/. The rcu read lock and > unlock calls in blk_queue_enter() form a pair with the synchronize_rcu() > call in scsi_device_quiesce(). Both scsi_device_quiesce() and > blk_queue_enter() must either use regular RCU or RCU-sched. > Since neither the RCU-protected code in blk_queue_enter() nor > blk_queue_usage_counter_release() sleeps, regular RCU protection > is sufficient. Note: scsi_device_quiesce() does not have to be > modified since it already uses synchronize_rcu().
Applied, thanks. -- Jens Axboe
