Hi ming Thanks for your kindly response. On 01/17/2018 02:22 PM, Ming Lei wrote: > This warning can't be removed completely, for example, the CPU figured > in blk_mq_hctx_next_cpu(hctx) can be put on again just after the > following call returns and before __blk_mq_run_hw_queue() is scheduled > to run. > > kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work, msecs_to_jiffies(msecs)) We could use cpu_active in __blk_mq_run_hw_queue() to narrow the window. There is a big gap between cpu_online and cpu_active. rebind_workers is also between them. > > Just be curious how you trigger this issue? And is it triggered in CPU > hotplug stress test? Or in a normal use case? In fact, this is my own investigation about whether the .queue_rq to one hardware queue could be executed on the cpu where it is not mapped. Finally, found this hole when cpu hotplug. I did the test on NVMe device which has 1-to-1 mapping between cpu and hctx. - A special patch that could hold some requests on ctx->rq_list though .get_budget - A script issues IOs with fio - A script online/offline the cpus continuously At first, just the warning above. Then after this patch was introduced, panic came up. Thanks Jianchao
