Effectiveness of workqueue cpumasks.

[GElliott]

The real-time profile includes the following settings:

[sysfs]
/sys/bus/workqueue/devices/writeback/cpumask = ${not_isolated_cpumask}
/sys/devices/virtual/workqueue/cpumask = ${not_isolated_cpumask}
/sys/devices/virtual/workqueue/*/cpumask = ${not_isolated_cpumask}

Do these settings have any effect, in practice? Setting these values does not appear to change the affinity of any currently running workqueues, even the unbound ones. Do the settings only take effect after a kernel module with a work queue is reloaded? I don't believe tuned is at fault---it appears to me that the kernel exposes these knobs with nothing attached on the other side. Am I mistaken?