Hello Jens, The five patches in this patch series fix the queue lockup I reported recently on the linux-block mailing list. Please consider these patches for inclusion in the upstream kernel. Thanks, Bart. Changes between v2 and v3: - Removed the blk_mq_ops.restart_hctx function pointer again. - Modified blk_mq_sched_restart_queues() such that only a single hardware queue is restarted instead of multiple if hardware queues are shared. - Introduced a new function in the block layer, namely blk_mq_delay_run_hw_queue(). Changes between v1 and v2: - Reworked scsi_restart_queues() such that it no longer takes the SCSI host lock. - Added two patches - one for exporting blk_mq_sched_restart_hctx() and another one to make iterating with RCU over blk_mq_tag_set.tag_list safe. Bart Van Assche (5): blk-mq: Make it safe to use RCU to iterate over blk_mq_tag_set.tag_list blk-mq: Restart a single queue if tag sets are shared blk-mq: Clarify comments in blk_mq_dispatch_rq_list() blk-mq: Introduce blk_mq_delay_run_hw_queue() scsi: Avoid that SCSI queues get stuck block/blk-mq-sched.c | 60 +++++++++++++++++++++++++++++++++++-------- block/blk-mq-sched.h | 16 +----------- block/blk-mq.c | 68 +++++++++++++++++++++++++++++++++++++++---------- drivers/scsi/scsi_lib.c | 6 ++--- include/linux/blk-mq.h | 2 ++ include/linux/blkdev.h | 1 - 6 files changed, 111 insertions(+), 42 deletions(-) -- 2.12.0