On Thu, Apr 11, 2019 at 01:34:46PM +1000, Nicholas Piggin wrote: > This patch provides an arch option, ARCH_SUSPEND_NONZERO_CPU, to > opt-in to allowing suspend to occur on one of the housekeeping CPUs > rather than hardcoded CPU0. > > This will allow CPU0 to be a nohz_full CPU with a later change. > > It may be possible for platforms with hardware/firmware restrictions > on suspend/wake effectively support this by handing off the final > stage to CPU0 when kernel housekeeping is no longer required. Another > option is to make housekeeping / nohz_full mask dynamic at runtime, > but the complexity could not be justified at this time. Should we not tie this into whatever already allows an achitecture to hotplug CPU-0? For instance, x86 default disallows this but has cpu0_hotpluggable to allow this. Presumably POWER already allows hotplugging CPU-0 ?
