On Mon, Aug 21, 2017 at 03:49:51PM +0200, Laurent Vivier wrote:

cpumask is the list of CPUs present when the queue is built.
If a new CPU is hotplugged, this list is not updated,
and when the scheduler asks for a CPU id, blk_mq_hctx_next_cpu()
can return WORK_CPU_UNBOUND.
And in this case _blk_mq_run_hw_queue() can be executed by the new CPU
(that is not present in cpumask) and raises the following warning:

    WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
            cpu_online(hctx->next_cpu));

To fix this problem, this patch modifies blk_mq_hctx_next_cpu()
to only return a CPU id present in cpumask.

So, this one isn't needed either.

Thanks.

-- 
tejun